1998 subaru overheat !!!

[subarunut]

hello all i have a big issue my Subaru legacy ej25d coolant heat rises drastically but it will idle forever at normal temperature 160ish and once i go anywhere like around the block the coolant goes up 234 on the scan tool i replaced the water pump and the thermostat the head gaskets were replaced at 201791 miles and currently i think i have 202ooo i think i put 200ish miles on the car since i rebuilt the engine im running just water through the cooling system and i havent had a problem i was going to flush it and put coolant in but then this came up the original scenario was 180ish miles after rebuild i went shopping with my mother "to test the practicality of my everlasting Subaru" and i went probably 17 miles overall then on the road it died at a traffic light i turned my music off right before and i thought i heard a tick tick tick at the light before i said that doesnt sound good i looked at the gauge it read right below half it looked fine i saw the rpms were wicked low then it died i didnt know why after a police officer pushed me out of the road i went and looked the radiator cap wasnt on i wAS pissed and i called my father to bring coolant and a cap bought a new one cuz we didnt have a perfect fit

HERES THE KICKER
new head gaskets
camseals
timing belt
water pump
thermostat
radiator was just flushed when the engine was apart it had stop leak in the sleeves scraped and blew that out
entire system doesnt have a leak pressure tested it hoses are clear
the top hose is warm and the hose after the pump an thermostat is cold most of the time both tank on the radiator are about the same temp
bleed screw doesnt leak but when unscrewed does leak steam after a few turns
radiator cap was cold after reaching temps of 230s
coolant resvoir was almost completely full
my fater (mechanic of 40+ years ) and i (soon to be mechanic) are stumped on this all parts work fine thermostat opens in hot water and the impeller on the pump doesn't spin when car is off(its attached to the timing belt so it wont move)


PLEASE HELP IM FURIOUS AT THIS CAR I CANT FIGURE THIS OVER HEAT ISSUE OUT

[Dead91silvia]

Sounds like you need to burp it more... I just had a customer call me tonight about the same thing with his XT OB. Most likely has some air in the system, even more so if the cap is cold and the motor is hot.

[subarunut]

I also suspect a faulty or just a cheap cap i needed one to get me home from my resting spot so i think im going to buy oem part and i will burp it more is there something i might be missing that is specific to Subaru bleeding procedure? also the lower radiator hose is cold after running but it was getting warm just before i left the house to run it around the block and the upper hose is always warm after its been warmed up i found that could be a thermostat issue but mine is perfectly functional any thoughts on this ?

[harrymaneuvers]

Are you 100% certain that your thermostat was an OEM one and not a Napa/Autozone/Advanced thermostat.

There is s pretty significant difference between them and I have first hand experienced this. Car warms up just fine at idle and then once I would start to drive it... it would start to overheat within a couple minutes or sooner.

Try taking your thermostat completely out of the car, reassemble and burp the system. If you can drive it around without overheating... it was your thermostat.


Difference:

https://sl-i.net/FORUM/images/imported/2010/08/DSC00412JPG-1.jpg

[subarunut]

But I never had a problem for 170 miles it never went above 1/2 way with the dura last part I am pretty sure it is the radiator cap so ill change that but if the oem cap doesn't work ill go get an oem radiator cap

[Cleck]

Are you 100% certain that your thermostat was an OEM one and not a Napa/Autozone/Advanced thermostat.

There is s pretty significant difference between them and I have first hand experienced this. Car warms up just fine at idle and then once I would start to drive it... it would start to overheat within a couple minutes or sooner.

Try taking your thermostat completely out of the car, reassemble and burp the system. If you can drive it around without overheating... it was your thermostat.


Difference:

[img]*snip*

Sorry to revive an old thread, but...

I'm having the same problem, replaced my t-stat as well, and I can drive around without it and have heat/no overheating, but as soon as I put the t-stat in, it didn't get heat and it overheated. My t-stats look just like the ones in your picture, what's the difference? I tested my new one in boiling water and it opened right up at 170°F as it is supposed to. Why does the design make a difference?

[harrymaneuvers]

Because the smaller design has 3 relativly small openings through the top for coolant to flow where the OEM one has two really large openings. It just cannot move coolant through it as quickly as the OEM one.

[Cleck]

Hmm that's interesting. When I tested it the other day, it seemed to have one pretty big opening when it did open. Granted, I did not test the oem one to see if the opening was different/larger/comparable, etc. Maybe I should. Either way, I think my oem one was still good, I just replaced it when I did a coolant flush recently.

[98legacygt22]

My gt wagon did this last winter after I changed the head gaskets. Park the nose of it on a hill and crack the little bleeder on the top passenger side of the radiator.

[unsullied_spy]

Sorry to revive an old thread, but...

I'm having the same problem, replaced my t-stat as well, and I can drive around without it and have heat/no overheating, but as soon as I put the t-stat in, it didn't get heat and it overheated. My t-stats look just like the ones in your picture, what's the difference? I tested my new one in boiling water and it opened right up at 170°F as it is supposed to. Why does the design make a difference?

Go to your nearest dealer and buy a new radiator cap. I've had issues with my car overheating for nearly two years (including a new cap from the dealer) and put in a new cap on Friday and ever since then my car has cooled perfectly. The gaskets on the cap I removed looked perfect and the spring tension was identical to the new cap but somehow that fixed my problem--either that or something happened simultaneously with the cap replacement. Either way it's cheap and easy to replace!

When your car overheats with the T-stat in how hot is the lower hose? It should be warmish or hot to the touch. Otherwise it's either a cap, T-stat, air bubble (or HG), or a plugged heater core. Air bubbles can be a bugger in these cars but if you jack up the front end, let it idle with the cap off until the fan(s) come on, put the cap back on, and let it cool completely you can bleed 95+% of the air from the system. Over a few days of driving it should bleed the rest out on its own.