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Overheating WRX!?!?! I'm LOST...

5064 Views 18 Replies 6 Participants Last post by  Cribbtay04
Okay so I'm at a complete standstill with this and only have a few more options that I can think of that is causing this overheating problem. I've never posted on here until now and wouldn't be if I wasn't seriously lost.

So here's some background. I bought this 2005 Subaru WRX wagon stock with a accessport and that's it. (I was told the timing belt needed to be done in the next 20k miles range). I have had it for a while and decided to get some more power out of it so I purchased and installed a turboXs tmic, 18g blouche turbo, sti 565cc injectors, catless uppipe, invidia high flow catted downpipe, spec-d catback exhaust, 255 walbro fuel pump, grimspeed boost control solenoid, and I could be missing some stuff but you get the point.

Within the time I installed all these parts, my friend broke one of the plastic nipples on my upper coolant expansion tank so I had to jerry rig a metal one from a 99' jdm sti (i believe)... so idk if this might have anything to do with it...

I limped my car in to get a protune and on the first day they noticed my injectors were leaking fuel out of the o rings so I limped in back to fix this issue (I know how stupid this is so I don't need crap for it haha). So after that problem was fixed I brought it back in to finish the tune and low and behold my lower coolant return line decided to start leaking so stupid me drove it 20+ miles overheating (no coolant) on the highway to change that out with oem spec tubing.

Now I haven't returned to finish the tune since then because now I don't have that leak anymore but my car seems to love to overheat not 5-10min after driving it from dead cold. So I'll start her up from cold and let it reach operating temperature and all the while my heat is working fantastic... then i'll go drive and as soon as I reach a stop my heater goes dead cold and my temp gauge skyrockets to the red zone.

So here's what I have done to try and address the problem:

1. I've bled and replaced the coolant on more than one occasion (yes I know the subaru filling and burping method and have done this every time)

2. I check my A/F ratio to make sure I'm not running too lean or rich and my optimum is around 14.7 which I've been told is what you want ideally.

3. I've checked all my fuses for the radiator and fans.

4. I've replaced the thermostat and radiator caps.

5. My fans do come on at operating temperature at a standstill with no overheating but I haven't checked the fans after the car overheats yet.

6. I've tested for Headgasket failure and all tests have come back negative. I used the block tester, have used the pressure gun to make sure air isn't being let it or introduced into the system, and I don't have ANY coolant leaks or white smoke from the exhaust.

7. I've checked for crimping of any of the main radiator hoses and haven't noticed anything (this is also at a standstill, haven't checked them after the fact of it overheating)

Now here's what I'm left with that it might be:

1. The water pump might be slipping, or I damaged the impellers driving it so hot for so long, or it has air lock. If I can't figure out anything else to fix it, I'm probably going to result in changing this water pump and timing belt out to see if that helps anything. The water pump has no noticeable leaking.

2. I have a bad radiator. I feel like this is unlikely because the previous owner installed a much larger one than stock but I am unaware on how long ago... I still don't think that much sediment could be built up in so little time.

3. I have a bad heater core. (no leaking noticed)

4. I'm getting SUPER BAD heatsoak... which i also think is unlikely to cause so much overheating but i'm not trying to rule anything out.

All these things must be a real strange coincidence that they went out right after I chose to mod my car or I messed up my car myself while either installing or driving it like a dumb***.

Now I've tried to do as much research as possible and I'm still really confused on what it could be. I tried to include as much information as possible but please please PLEASE let me know if I need to add anything to better understand my situation because I really really do need help. Thanks so much in advance!
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Before anything else, are you at least running a base map from the shop you took it to for the upgraded injectors? You talk about having a Cobb AP, but there is no calibration that they offer for 565cc injectors.
Right. I'm not running any OTS maps. I am currently on the protuners custom made map (from off a dyno), it's just not finished
You could have air in the lines, bleed it. Then bleed it again, then once more for good measure. The symptoms sound to me of a air pocket getting caught at the thermostat or the heater core or both

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^^^Try this. And then if you're still struggling changing the water pump and timing belt could possibly kill two birds with one stone. That job would still get the timing belt done and a new water pump but that's a risky gamble assuming you can fix this issue plaguing the engine. GDs can get finicky sometimes. Trust me i've been there.
Thanks for the quick reply from you both! Any ideas for purging the air from the system? Or draining the system COMPLETELY and then how to refill the car without having air get into the system?
There are special funnels that attach to the radiator caps that you fill start the car and let burp out. You'll want to use the highest point in the system, and since you can't bleed from the heater core the radiator or the reservoir near the turbo

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Okay sweet. Yeah someone from my NASIOC post said to try using one of those lisle funnels so I'll give that a try. Thanks again
UPDATE: Okay so here's an update. I changed out my timing belt as well as my water pump and put in the OEM thermostat. As the car now takes a bit longer (couple minutes) before overheating... it still does so.

What I found interesting is that when it overheats, only the top 1-2inches of the radiator are hot and the rest of the radiator is like cold cold.

Please lmk if this changes something. Thanks
Poor circulation. You may have a clogged radiator or an air pocket in it.

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What do I need to do to fix that then? I took the radiator to a shop (with it out of the vehicle) and had them flush it and they told me that it had good flow. I've burped the system many of times and I still can't seem to solve the problem. Thanks!
I also purchased that lisle funnel and have been using that every time I attempt burping it.
Where are you burping? At the radiator or at the high point by the turbo?

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Ive burped multiple times from both the upper expansion tank and the radiator itself. I've also tried jacking up different sides of the car to kind of coax air out but to no avail...
It may be time for a water pump. I'm not sure where else to check besides possible stuck thermostat.

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Something does not make sense. If only the top portion of the radiator is hot, the rest is plugged up not allowing flow. If the shop told you it had good flow, they didn't know what they were talking about.
Just replaced the water pump in conjunction with the timing belt and it did not fix the issue.

I too thought that the shop might have not done a very good job, so I tried running my garden hose water through it and it seemed to flow perfect fine to me. No gunk came out either.
I found this. Don't know what your aftermarket radiator is, but perhaps you still do not have the correct cap on it???


The provided Mishimoto radiator cap should replace the stock cap located on the expansion tank. The stock cap attached to the radiator should be installed on the Mishimoto Performance Aluminum Radiator. The Mishimoto radiator cap is a two way valve, while the stock radiator cap is a single valve. Due to the difference in construction, the Mishimoto cap cannot be used on the radiator. If the Mishimoto cap is fit on the radiator, overheating may occur.
Op was there any resolve to this im having the same issue with my 06 wrx tr
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