Hi, I'm new and I need substantial help here..

[ShadowGT]

Hey there, my name is Dennis and I'm from the gulf coast of Texas.
Sorry for the long post you're about to read.

I lost my car in hurricane Ike. I bought a 98 Legacy GT Wagon from a local pastor for 500 bucks. It has 140,000 miles, well plus 600 that I put on the car.
The man I bought it from pulled the engine out, rebuilt it, machined the heads and valves, put a new head gaskets on and so on. The car is pristine except for a crack in the front bumper and a door ding. Even the interior is flawless.

The car has issues that I resolved except for a few that I need advice with.
Here we go:
The car leaked oil from the valve covers. I put new valve cover gaskets on, problem solved.
The air intake box was cracked to pieces.. I installed a Cosmo Racing / ebay CAI. It has all the right parts and vacuum hose ports in the right places. Installed MAF collar after the filter,all that works fine. (Loud as hades though)
I changed the cone filter to a universal KN cone filter, replaced every vacuum hose with Goodyear fuel / emission hoses.
Changed the front O2 sensor.
Changed the neutral switch sensor
Changed the camshaft position sensor
Installed a Kartboy short throw shifter and polyurethane bushing kit.
Put my JVC CD/MP3 stereo head in the car because I have no use for the tape deck.. as retro cool as that may be.
Put new belts on the car, reinstalled the shrouds.
Installed NGK sparkplugs and Beck Arnley Blue Thunder plug wires.
Removed the hood scoop blocker so my CAI can breathe.
Installed engine coolant temp sensor
Installed new thermostat.
Installed salvaged Air Idle Controller and solenoid.
New throttle position sensor.
Walbro 225 fuel pump


So the car had a lot of work done between myself and the pastor I bought it from. Carfax verifies he was the sole owner and was never wrecked

Problems:
The car drives like a raped monkey. That's a good thing.
Except from time to time the car feels like I'm dragging an anchor behind me, loses power and bogs down then dies.
Car runs well.. but randomly just loses power and dies. Restarts just fine.. then loses power again and dies. This goes on and on.
When I got the car, it couldn't run 5 feet without dying. It looks like I bought a bunch of random parts but there was a method to the madness and now the car runs.. not well but better.

I have an elm327 ODBII interface for my laptop. I use Scantool for diagnostics. I tested Scantool on my wife's new Hyundai Tucson, everything works right and reads correctly.

On the Legacy.. not so much.
Misfires on all 4 cylinders. Clear them out, get the codes right back.
Neither O2 sensor shows data or voltage information. Scantool can read the truck's so I know what I'm looking for.. but neither O2 sensor on the Legacy.. not even the new Bosch one I put in reads back data.

Car starts in open loop mode. I know.. weird.. Stays mostly in open loop mode in idle.

Occasionally get a warning on Scantoon saying that there is a ground or VBatt fault but only when hooked to the Legacy. I never see that when plugged into the truck.

The Elm327 constantly loses communication to the Legacy ECU. But not the Tucson.

So now what?
When the car runs.. believe me it does run.. it runs awesome. Sounds awesome. Just from time to time it bogs down and every miss fire burns a lot of fuel.
I know the car is running rich. The catalytic converter gets very hot and makes that heat-ticking sound.. more so than any car I've ever owned.

I know this is a hell of a first post but I'm lost here.. love this car. It's really super nice. It had a lot of problems and I chased them all down except for this one.

Anybody have any ideas? Bad ECU? Bad wiring? I have a voltmeter, I also have a Haynes book and the shop manual for the car.
Just need to know where to look and how to check this.

Sorry for the long epic post. I've lurked this site and Scoobymods for a long time. I just felt like being a member now and farm some knowledge from you guys.

Thanks,

Dennis.

[decke48]

welcome.
as for the problem. it sounds like a bad ecu. cant really check for it either only to replace with a used unit and see if it goes away.

[ShadowGT]

Hey, thanks for the welcome.
Yes.. this ECU thing is something I feared. I suspected I would run into this problem but I wasn't looking forward to it.

Love the car. Absolutely love it. Don't mind working on it, don't mind doing stuff to it.

I guess my concern now really is where to find an ECU that I can be sure it works and doesn't cost a fortune. Yeah theres eBay and car-parts.com.

I need to think about this. At first I thought it was my Elm327 that wasn't working but my wife's truck proved that wrong.

For what its worth, I'm impressed with this forum. So much information, so much stuff already answered that I had questions for. Nice place.

[Huffer]

Does the car randomly switch off while driving? In that case I would check your ignition switch - do you have a heavy bunch of keys?

[ShadowGT]

Hi there,
No it doesnt randomly switch off per-say.
My key ring consists of two car keys, two remote fobs and a house key and a gun locker key. (I work for the government.. I'm armed from time to time.)

So my key ring isn't inadvertently switching the ignition off by vibrating a connection loose.

When the car dies while driving it starts with the misfire. It starts sputtering while driving.. doesn't matter if the car is hot or cold, it truly occurs randomly.
Sometimes it doesn't happen at all and I can get to where I'm going just fine and the length of the trip doesn't matter either.

So.. on track here..
Car starts to sputter. I lay on the gas to keep it running and I become Spy Hunter and I emit a long stream of a black smoke screen from the back of the car. Not burning oil.. smells like burnt gas / rich combustion.
That's when the anchor dragging feel / deployed parachute feel starts.

If I let off the gas.. sometimes it just returns to idle but starts bouncing from 700RPM to 1200 RPM.
If the RPM's fall fast enough, the car shuts off completely and takes a second to restart.

It'll happen when idling or while cruising down the highway. I tried using cruise control, it holds just fine.. the misfires occur "quickly" in cruise control.
Not just one prolonged event, it'll feel like several small sputters.
It hasn't died in cruise control, but I haven't been trying to make it die in that mode either.

For what it's worth:
The air idle controller is good. I cleaned it up with carb cleaner. The valve moves freely without resistance. I put good gaskets on it. The solenoid works, gets voltage and I can actually adjust the idle speed by moving the solenoid "twisting" back and forth.
I set it right so that the car does idle at 700 RPM under load with the AC and lights on. The car compensates AC on and off by adjusting the idle. It hovers at 700 until things start to go wrong and the misfires occur.

I'm no longer getting MIL/CEL codes from the ECU. The car has died twice on the way to work by prolonged misfires and it used to register the 4 codes for the cylinders. That doesn't happen anymore.

I'm not sure if the engine thinks that's normal now since I reset the ECU through Scantool last night.

I would like to blame the ECU. It'll make my life easier to just replace it.

[anothernord]

Possibly check the electrical connections to the ECU? If those are all good, check the ECU internals to make sure there's no moisture buildup or shorting. It sounds like you have already taken care most of the failure-prone parts so the ECU could be the culprit. Check eBay or a salvage yard for a new unit.

[Huffer]

I'd consider picking up a MAF sensor too and see if that'll help.

[ShadowGT]

Possibly check the electrical connections to the ECU? If those are all good, check the ECU internals to make sure there's no moisture buildup or shorting. It sounds like you have already taken care most of the failure-prone parts so the ECU could be the culprit. Check eBay or a salvage yard for a new unit.

Aha.. See.. I get into this broad minded mode where sometimes I don't really consider small things sometimes.
Pull the ECU, look at it, inspect it.. I guess clean it somehow and put it back in.

At the age of the car, considering the engine has been pulled out of the car and all I suppose the ECU would be something worth replacing. Just hope I know what to look for when seeking a replacement.

Somehow it can't be as easy as saying "yeah, need a 98 Legacy 2.5 GT ECU, it has a manual transmission."
If having a manual transmission has any bearing on the type of ECU.

As for the MAF sensor..
Probably wouldn't hurt. Already changed so much in the car, why not? A salvaged unit isn't expensive. Already saw those on eBay.

The current one in the car does show a signal on Scantool, at idle in close loop while warmed up the sensor read .8 lb per minute at 850 RPM, calculated engine load at the time was 5.1 percent, throttle position 0, timing advance 15 degrees.

But.. why not get a new one. After all that's been done so far I guess this car will last damn near forever after this. :smile:

Which is good.. because I like the car.
I almost bought a BMW 323CI instead of this car but the exterior was a little more rough looking in places and I realized that doing home mechanic work on a Bimmer would be an uphill battle.

But all in all.. when the Scoobie is running right, it feels very good and confident.. just like that 323CI.

By the way.. this is going to sound very vague, but bear with me.
Under the driver side dashboard there are two little wire connections that are unplugged. They look like they fit together but are not plugged together, just hanging side by side. Smallish.. like what you would see in a computer tower. Right above the brake pedal.
Anybody knows what that is? I don't want to randomly plug stuff in without knowing what I could be doing.

Considering I'm here at work, don't want to blow something out and strand myself here at the center.

[Reason]

Find someone parting out a car with the same engine. Average it would be $50, at most $75.

[ShadowGT]

Find someone parting out a car with the same engine. Average it would be $50, at most $75.

Will do.
I've already called all the salvage yards in the area I live in and the answer was usually "we've never had a Subaru in the yard".
The closest Subaru place is Baytown, 90 miles away.. just to give the general idea of what's around me. To be honest, I haven't seen a Subie other than mine.
Plus after the hurricane, I'm very leery of cars being parted or sold because of flooding issue.

But I'll look around on other boards and what not. I imagine I'll stumble over a reasonably priced one by Thanksgiving.

[Huffer]

Under the driver side dashboard there are two little wire connections that are unplugged. They look like they fit together but are not plugged together, just hanging side by side. Smallish.. like what you would see in a computer tower. Right above the brake pedal.
Anybody knows what that is? I don't want to randomly plug stuff in without knowing what I could be doing.

Considering I'm here at work, don't want to blow something out and strand myself here at the center.

DO NOT PLUG GREEN PLUGS TOGETHER.
Those are diagnostic plugs and will put the car into a limp mode.

[anothernord]

+ 1 for replacing the MAF. The filament wire is very delicate and doesn't tolerate much abuse. Plus they're cheap and it would be another part out the the equation.

[ShadowGT]

Under the driver side dashboard there are two little wire connections that are unplugged. They look like they fit together but are not plugged together, just hanging side by side. Smallish.. like what you would see in a computer tower. Right above the brake pedal.
Anybody knows what that is? I don't want to randomly plug stuff in without knowing what I could be doing.

Considering I'm here at work, don't want to blow something out and strand myself here at the center.

DO NOT PLUG GREEN PLUGS TOGETHER.
Those are diagnostic plugs and will put the car into a limp mode.

Lol.. those were green. I was using my little tactical light which puts out a blue LED. Wait till daylight.. yeah those are green plugs under there.

I'm off work this weekend, I'll use that time to extract the ECU to see what the part number is and see what the general conditions are like under that kickplate.

Meanwhile I'm going to find that MAF sensor collar thingie.
In other news, my car has completely baffled me. On my way to work yesterday evening my car misfire and I had to pull of the road for a bit to let the car calm down before continuing the 22 mile commute.
On my way home this morning after my shift, the car ran home perfectly with no problems. I even let the car idle in my parking spot to finish listening to a song on the radio and the car never missed a beat.

On my way back to work, it ran like a champ.. I stopped a quickie-mart to get some Mountain Dew and a pack of smokes for the shift and for the last three blocks from the store to work the car ran like total crap.
I was in the store for a grand total of 5 minutes.

There is no rhyme of reason to this problem, I can't even recreate the situations. Sometimes it runs great.. sometimes it runs awful.

But yes.. this weekend, I'll be on a mission to locate, extract and inspect the ECU and tonight I'll look for that MAF.

[anothernord]

Sounds like a good plan, let us know how it turns out!

[Plays_with_Toys]

Things I would be checking...

1)MAF
2)Throttle position sensor, helped a local girl here replace that as she was having a misfire in two cylinders and it cleared up.
3)Check spark plugs. Didn't see that you replaced them. If you did replace them, and you didn't replace them with NGK or Denso's then replace them again.
4)Check the connection to your coil pack, check that all the spark plug wires are seated.
5)I'm afraid to ask- is the car overheating at all? Have you checked the temp gauge when this is happening?
6)He pulled the motor. Did it have these problems before it was pulled? Are you confident in his timing belt abilities?
7)PCV
7)SEAFOAM that biyotch. Give it a good 12 hour soak time before restarting it. I think i sucked it down the PCV line on mine revving up around 1800-2000, and cranking the engine up more when it'd bog down. Check the seafoam thread on here, but half through the vacuum line half a nearly empty tank, drive to fill it up.

[ShadowGT]

Things I would be checking...

1)MAF
2)Throttle position sensor, helped a local girl here replace that as she was having a misfire in two cylinders and it cleared up.
3)Check spark plugs. Didn't see that you replaced them. If you did replace them, and you didn't replace them with NGK or Denso's then replace them again.
4)Check the connection to your coil pack, check that all the spark plug wires are seated.
5)I'm afraid to ask- is the car overheating at all? Have you checked the temp gauge when this is happening?
6)He pulled the motor. Did it have these problems before it was pulled? Are you confident in his timing belt abilities?
7)PCV
7)SEAFOAM that biyotch. Give it a good 12 hour soak time before restarting it. I think i sucked it down the PCV line on mine revving up around 1800-2000, and cranking the engine up more when it'd bog down. Check the seafoam thread on here, but half through the vacuum line half a nearly empty tank, drive to fill it up.

1. Though the current MAF was showing 8 pounds of air at idle through Scantool, I ordered another one and it will ship tomorrow. I figured why not, it was cheap and supposedly guaranteed to work. Eitherway I'll just get that out of the way.

2 TPS is brand new. Just put that in the car last week. I made sure that the rotating bar on the throttlebody side aligned with the rotating bit on the sensor while the car was off.
3. Spark plugs are new, they're NGKs.
4. Coil pack is plugged in, I pulled it off, inspected it - looked fine, reseated everything from the input to the plug wires.
5. I suspected the car might be oveheating but could never confirm it. The waterpump is new, was installed when the engine was pulled. I put a new thermostat in and I replaced the ECT sensor. (That was a bundle of fun) I even flushed and replaced the coolant for good measure.
6. Timing is good, doesn't slip or jump. A mechanic did the timing when original owner put the engine back in.
7. I put in a new PCV valve. Original didn't rattle.
8. I seafoamed the fuel system, but didn't put any in the air tract. Will consider that after I check the ECU this weekend and I install the new MAF.

So I'm right there with you, man.
I'm confident I'm going to resolve this soon so I can move on to better things.

[ShadowGT]

Sorry for the double post. At least it wasn't back to back, enough time has passed.

Here's an update.

I pulled the ECU. If you want me to do a write up, I'd be glad to do so. I'll say this, the Haynes book seriously over complicates the process.

Got the ECU out, it is in great shape and visibly / physically there was nothing wrong that I could find. Doesn't rattle in the inside, nothing appearing out of place, nothing burned. The wire harness, which makes no sense by how the Haynes book describes it was alright, nothing pushed out of place.

After reinstalling the ECU I decided to slightly adjust the air idle controller solenoid. Cranked it open a degree or two and ensured I have no vacuum leaks anywhere.

More on the ECU later.

I sea-foamed the air intake. Four ounces into the PCV valve using a small plastic small engine gas / mixing tool. Just slowly fed the elixir in. The engine was practically sucking it out of the syringe tool.

Poured the remainder mostly into the half full gas tank and a small bit into the oil fill spout.

Waited..

Restarted and behold the smoke screen.

The car has been running great all day. Been running errands with it and it has been smooth as silk with stop and go's and highway running.

Back to the ECU. Still convinced I have a faulty ECU. Scan tool only reads the first page of information. MAF appears to work despite that I have a new one on the way. I unplugged the MAF while the car was idling and the car died. Plugged it back in, restarted and cleared the code from the engine. Car was fine.

Scantool can not read the O2 sensors. As far as I know, the car is not getting proper information if any from either O2 sensors. There is some information appearing before the data stream halts. I briefly see the mili-volt inputs and they appear in parameter before the data stream stops.

Since reseating the ECU, I'm not getting VBATT or ground faults from Scantool.

Tomorrow with good daylight I will undo the Bosch universal O2 sensor wire splice set up and use a normal crimp-collar set up. Maybe something is wrong with that box from hell set up Bosch gives you to splice the wires together.
Perhaps because the second O2 reads from the first O2, because bad info is coming from the new first O2 sensor, the 2nd isn't doing anything.

I found the main junction in the wiring harness where the O2 sensors join the rest of the car wiring and goes to the firewall. It's that giant bundle of shit for wires that sits behind the AIC. I unplugged the O2s and reseated them.

I think the car runs well now because the weather has been favorable, therefore the car is less likely trying to switch from lean to rich to compensate for temperatures. The car is idling in closed loop mode for what it's worth now.

We'll see what happens tomorrow when I resplice the front O2.

[anothernord]

Nice work! Keep the info coming; It looks like you're on the right track. And If all else fails, you can always turn in your man card and take it to a Subaru dealer or shop. Good luck!

[Huffer]

Solder the O2 wires, don't crimp.

There's likely nothing wrong with your ECU, typically the sensors (various) go bad which create faulty readings. Its like if you lost one of your eyes, you could still move around but your depth perception is all messed up.

Don't forget to check your plugs after seafoaming and give it a fresh oil change too.

[Okin DaVanh]

Yout's why I asked. also mentioned you had a K&N.... Not oiled, is it? I had a nightmare happen to me when I tried, tha

[Zedhead]

Didja calbrate the TPS when You installed it?

.5V throttle plate closed, 5V wide open.


It sounds suspiciously like the ECU. If It won't come out of open loop, when warmed up.

It might be going closed when the engine starts running like crap? Do You have the capabilities to monitor it while driving?

[ShadowGT]

Update:

All is well in the world.

For starters, I traced a ground wired from the ECU that attaches to the chassis in the engine bay. It was loose, the screw holding it in had backed out. Don't know why, probably something to do with the previous owner taking the engine out of the car. I cleaned it up and put back to the chassis properly. Ran Scantool, still no mysterious fault errors and suddenly all the sensor data that was previously unavailable had now become visible.

The MAF sensor looked suspicious because of some low readings of pounds of air being pulled through past the sensor and the oxygen sensors were still a no-show on the Scantool.

My new MAF (salvaged) came in and I just tossed that on. Scantool shows 10 pounds at idle being sucked past the MAF.
OK..

Bought another O2 sensor to replace the rear downstream sensor. I removed all the stupid Bosch box style wire connectors and used the crimp connectors I had. Yes, solder is better. But I don't have an extension cord long enough to reach out of my apartment to go to my covered parking stall in front on my apartment. (think townhome.. just no actual garage)
I know theres a butane solder iron and a cold heat-battery iron..

Don't like the idea of using the butane iron underneath the car. I'll consider other options later on.
Point is.. the removing the box connectors and using the crimp connectors work perfectly for now.

First O2 sensor, I bought apparently had a bad connection with that insipid box connector set up they want you to use. Skipping that and going straight to the crimp style for the second bypassed that problem.

Checked Scantool, voila' now the O2 sensors are reading on Scantool.. except the second O2 sensor was showing 1.2 volts constant. Not good.

Working at night, with a flashlight underneath my car I somehow reversed a sensor wire and a heater wire. I changed that connection back to normal, ran scantool again.. perfect. Now both O2 sensors read and fluctuate between .2 and .8 milivolts.

Also..
After redoing the ground wire I found, I did find a code that immediately popped up that never appeared before. "Air idle control idle speed higher than expected."
Yes, before I had increased the idle speed by rotating the solenoid a few degrees to try to stop the bogging down while I figure out everything else.
So now that it appears and is recognizes, I believe the ECU works properly. I dialed the AIC back to around 770 RPM at load, with AC, lights and radio on.
Engine idles with load at 4%.
Turn everything off and the car idles at an even 700 RPM, 4%.
That was after resetting the ECU with Scantool and then unplugging the car battery to make the car relearn.

To answer a previous question, the KN filter is oiled. Well, preoiled. It's brand new, never had to re-oil it yet.

Drove the car 200 miles past few days, starting and stopping, hot, cold, fast slow, highway, traffic, on, off, so on and so forth and the car has not missed a beat.
No smoke screens, no hesitations, no misfires, no bogging down. Best of all, no error codes.

I am convinced to a satisfactory degree that all is well under the hood electrically and mechanically.
Put my SLI stickers on the other day as well.

Now, all I need to do is track down the little things that bug me. Lights don't work on the AC control surface, power steering belt squeals now since the temperature has changed outside, power antenna doesn't retract all the way down.. just to the last segment, sunroof leaks in a car wash but not in the rain.

Oh yeah.. clutch hydraulic pressure.. every two weeks I have to remove the push rod from the clutch pedal and manually pump up the pressure in the slave cylinder then reconnect the rod to the pedal. Not leaking fluid out of the car.. Master cylinder stays full all the time. Something weird. Not end of the world, just annoying.

Now I can concentrate on those little things and stop wondering about the damn engine.

Thanks for all your input so far, guys. Its been challenging but we got past a major hurdle with the Legacy. Now it's fun to drive.

[Huffer]

Great to hear pretty much everything is working well now! The grounding system is one of those things that is truly underrated.


Now, all I need to do is track down the little things that bug me. Lights don't work on the AC control surface, power steering belt squeals now since the temperature has changed outside, power antenna doesn't retract all the way down.. just to the last segment, sunroof leaks in a car wash but not in the rain.

Oh yeah.. clutch hydraulic pressure.. every two weeks I have to remove the push rod from the clutch pedal and manually pump up the pressure in the slave cylinder then reconnect the rod to the pedal. Not leaking fluid out of the car.. Master cylinder stays full all the time. Something weird. Not end of the world, just annoying.

The lights not working on the HVAC unit is common. There's a DIY fix in the forum section.
PS belts can be tightened using the tensioner, power antenna can be replaced with a universal non-retracting one for cheap, or an OEM style for a bit more.

The sunroof could require a drain clean - there's a thread on how to fix that too.

The clutch slave cylinder probably needs replacing. At the same time you do that you might think about adding a stainless clutch line.

[Zedhead]

I duuno why Bosche uses that wiring set up. Why would you want to hack up the OEM harness? I used a new OEM O2 sensor up front. P&P.

[Huffer]

I duuno why Bosche uses that wiring set up. Why would you want to hack up the OEM harness?

Lower cost. Fabbing up a replacement sensor with exactly the right length of wire WITH a factory style plug is expensive and provides a limited sales base. Providing a semi-universal (3-wire) setup with a generic connection setup (which, if installed correctly and soldered, provides a weatherproof connection box) is a much cheaper production cost.

Personally I have used the Bosche setup twice and while it was initially a PITA, once I figured out the install process (cut wires, put box and grommets on, solder, slide box over top and seal, install sensor) it was smooth and lasted at least 60k. I saved $40 per sensor, that's just over 3 tanks of gas at current fuel prices for me.

*shrug*

[ShadowGT]

Great to hear pretty much everything is working well now! The grounding system is one of those things that is truly underrated.


Now, all I need to do is track down the little things that bug me. Lights don't work on the AC control surface, power steering belt squeals now since the temperature has changed outside, power antenna doesn't retract all the way down.. just to the last segment, sunroof leaks in a car wash but not in the rain.

Oh yeah.. clutch hydraulic pressure.. every two weeks I have to remove the push rod from the clutch pedal and manually pump up the pressure in the slave cylinder then reconnect the rod to the pedal. Not leaking fluid out of the car.. Master cylinder stays full all the time. Something weird. Not end of the world, just annoying.

The lights not working on the HVAC unit is common. There's a DIY fix in the forum section.
PS belts can be tightened using the tensioner, power antenna can be replaced with a universal non-retracting one for cheap, or an OEM style for a bit more.

The sunroof could require a drain clean - there's a thread on how to fix that too.

The clutch slave cylinder probably needs replacing. At the same time you do that you might think about adding a stainless clutch line.

OK, so a few hundred miles later everything is perfect. Car still runs great. Got that strut brace that I accidentally won off of eBay. That installed pretty quick, no fuss.

I saw the DIY fix for the HVAC. I'll be getting to that soon.

I did tighten the PS belt, no problem. The AC belt.. problem. The tensioner is broken as I discovered. The tension screw has broken away from the pulley slide. Well.. the slide on the pulley is actually broken so it won't tighten up. I'll look into fixing that later.

Sunroof.. still trying to figure out why it "hiccups" when I close the doors. The pressure change in the car causes the sunroof to shudder. Probably why it leaks under high pressure. Then again, it won't kill me to look at the drains too.

I found a replacement slave cylinder for 35 bucks. That and the stainless clutch line will be my next project. That and soldering the O2 wires together now that I'm convinced everything works right now.

See, now things get fun. I'm so happy the car runs well now.

[Huffer]

Sunroof.. still trying to figure out why it "hiccups" when I close the doors. The pressure change in the car causes the sunroof to shudder. Probably why it leaks under high pressure. Then again, it won't kill me to look at the drains too.

The hiccupping is normal, don't worry about it. I take my car through a carwash all the time. There's another cause for the leak, and the best way to tell is find out where the leak is coming from (what part of the roof) and trace it backwards. Do this soon, because rust is a PITA.