Head gaskets replaced, but still overheating?

[danci1973]

My '99 2.5 BH which started overheating when driving at higher speed for a period of time - ie. highway @3000 RPM (or more). After stopping, I had to refill the coolant (both the radiator and the reservoir were almost empty), but there was no smoke coming out of the exhaust.

If I kept the RPM below 2500 RPM (also avoiding hard acceleration) I could drive for weeks with no coolant disappearing and no other obvious ill effects.

Reading some info on this forum and also asking some mechanics / Subie dealers for opinion the verdict was - head gasket(s).

So I got the gaskets, took the engine out and removed the heads... Looking at heads, old gasket and cylinder block I couldn't see any evidence of a leak or anything similar. There also wasn't any oil in the coolant (now pretty much just distilled water) or water in oil - at least not in the amount that could be visible.

I had heads machined and the guy at the machine shop confirmed that one of the heads was slightly warped while the other was fine.

So I put it all back and went for a test ride - unfortunately the car still behaves exactly the same! Driving at 4000 RPM for a couple of minutes and the temperature starts rising... Taking the foot of the pedal the temp drops and I'm able to maintain normal temperature when driving at ~2000 RPM.

After stopping I checked the coolant - again, it has disappeared. I checked both pipes of the radiator and while the top one was HOT, the lower one (the one that goes to the thermostat which was replaced) was COLD! Not hot, not worm - it was cold.

Driving back home I kept the revs under 2500 and back at home, the water was still all there and both pipes were hot.

I haven't replaced the water pump and the radiator, but I can't imagine how these could fail in such a bizarre manner?

What is going on with my car?

Any other ideas??

D.

[Huffer]

Do you have a leak in your cooling system somewhere?

Check the radiator for blocks, check your t-stat is opening properly.

[danci1973]

Do you have a leak in your cooling system somewhere?

Check the radiator for blocks, check your t-stat is opening properly.
As far as I could see, there are no leaks... After filling the cooling system and bleeding the air out of it I moved the car to a dry location and let it warm up, just so I could see if any drops would come out of the engine - but there were none.

The t-stat has been replaced, even though old one seemed OK when I cooked it.

How can I check the radiator for blocks?


Today we (a friend of mine and me) just replaced the water pump (even though the old one looked OK, only a tiny bit rusty), but again - it didn't change anything. On the test drive the temperature started rising - I stopped immediately and we checked the coolant - it was bubbling a lot in the expansion reservoir and after opening the radiator cap (hot!), there was just steam. We re-filled it with distilled water and crippled back home - this time, water was still all there.

A friend of mine says that he can only think of three more options:


a warped block - it could be machined just as the heads were, right?[/*:m:3hxue70d]
a crack in the block[/*:m:3hxue70d]
a crack in the head[/*:m:3hxue70d]

I don't like any of these, but would settle for the first one...

However - before going through all the engine removal trouble again - is there anything else that could be causing this?

D.

[j_saffron]

Today we (a friend of mine and me) just replaced the water pump (even though the old one looked OK, only a tiny bit rusty), but again - it didn't change anything. On the test drive the temperature started rising - I stopped immediately and we checked the coolant - it was bubbling a lot in the expansion reservoir and after opening the radiator cap (hot!), there was just steam.

We re-filled it with distilled water and crippled back home - this time, water was still all there.

if you put the water in while it was still hot.


a crack in the block

just sayin.

[danci1973]

if you put the water in while it was still hot.


a crack in the block

just sayin.
Well, I didn't pour water in immediately (waited for 10 minutes or so) and I poured it in the radiator relatively slowly... But yeah, basically this could have happened AFTER the car initially started behaving in this manner.

Should I start looking for a replacement engine? The EJ251 (SOHC) seem pretty rare... :(

D.

[AR-45ACP]

Are you sure you dont have air in the system? That will definitly cause car to overheat. may not apply to subarus though......

[decke48]

if your loosing coolant. you have a leak somewhere. try pressure testing the system for leaks

[danci1973]

Are you sure you dont have air in the system? That will definitly cause car to overheat. may not apply to subarus though......
I filled the coolant 'by the book' and then some. I think there was no air in the system when we went for a test ride...


if your loosing coolant. you have a leak somewhere. try pressure testing the system for leaks
I'm not loosing coolant if I drive slow (ie. below 2500 RPM). If I go over 3000 RPM, it overheats in minutes, the coolant boils and gets pushed out through the expansion reservoir...

Things that have been done so far:


heads machined[/*:m:2gshmgwk]
head gaskets changed[/*:m:2gshmgwk]
radiator cap changed[/*:m:2gshmgwk]
thermostat changed[/*:m:2gshmgwk]
water pump changed[/*:m:2gshmgwk]

I'm slowly running out of options... :roll:

D.

[decke48]

fans kicking on?

[danci1973]

fans kicking on?
Yes.

Is there a method for checking the radiator for (partial) blockage? :smt017

D.

[danci1973]

Today a new radiator arrived. This was the last 'cheap' thing that could be replaced before giving up on this engine.

Guess what - it was the radiator. I just got back from a 150+ km test drive including all sorts of driving (fast, slow, uphill, downhill, ...) and it was OK - the temperature was rock stable just a hint under the middle (a reminder - before a 10 minutes of 130 km/h was all it took for the engine to overheat).

I think I learned a valuable lesson here - don't assume the worst possible scenario has come true. I could've saved a lot of money if I had gone through the whole thing systematically from the cheapest possibility (a T-stat probably) upward to the most expensive (replacing the head gaskets).

I hope it'll last for a while now.

Danilo

[Huffer]

Check the radiator for blocks, check your t-stat is opening properly.

I WIN! :D

Glad to hear it's better. Sorry no-one got back to you about pressure-testing the rad.

[danci1973]

Check the radiator for blocks, check your t-stat is opening properly.

I WIN! :D

Yes, you do! :)



Glad to hear it's better. Sorry no-one got back to you about pressure-testing the rad.
I still have no idea how I could test the radiator - since it's not leaking, what would pressure testing show?

It wasn't fully blocked either - now that it's out of the car I can pour water on the top and it comes out on the bottom with no noticeable problems.

I noticed some 'residue' on the walls of the expansion reservoir - as far as I could feel it with my fingers, it was pretty thick. I can imagine how this sort of build-up on the inside of the radiator can lower it's efficiency a lot.

I'm happy the car is back on the road (and in the fast lane). :)

D.

[danci1973]

Just in case someone is interested - it seems the problem was the 'neck' of the radiator, where the cap should seal. That inner surface was damaged (looks like erosion) and the coolant could flow freely into the expansion reservoir. Consequently there was no pressure in the system and when the temperature rose (due to higher engine load) the coolant would boil, pushing itself out of the expansion reservoir.

Here (http://foto.slovenija.net/index.php?album=%2FDanci%2FRazno%2FSubieforum%2FStari_hladilnik) are some pictures of the damage:

https://sl-i.net/FORUM/images/imported/2009/05/IMG_8165-1.jpg
https://sl-i.net/FORUM/images/imported/2009/05/IMG_8166-1.jpg

The 'orange stuff' is probably rust because in the recent months I was adding just distilled water and when I took the old water pump out, the impeller was pretty rusty.

I have no idea what caused this 'erosion' though. Maybe a bad radiator cap cause a small, but steady leak that did this?

Anyway, the car has been thoroughly tested by now. It also got a new clutch and single-mass flywheel in the process. :smt023

D.

[massdrewski]

I had the same problem with my 98 2.5 as it turned out the radiator was just junked up. It flowed but at higher speeds/RPM's, it was'nt getting enough flow. Replaced and now perfect.