What is causing me to overheat?

[Benjewman]

Some details, probably too many but meh.

 

I have a 2005 lgt, ~138k miles on the original block, og turbo replaced at ~45k miles.

 

I have had an overheating issue that started back in about 2018 and it is getting worse, mainly cus im driving the car more than ever, an hour commute each way to work/school and back.

 

My car only overheats when I'm driving slow, like in traffic, through a drive thru line, around a parking lot, stuff like that. Driving at speed or on the highway, no issues. When it goes to overheat, I will watch my temperature gauge slowly rise and it will go up to just around the red but never over, it will sit there for a second or two and then drop down to where it should be, a smidge below the middle. This would happen randomly and infrequently, so i didnt worry too much. Although I did look into it and some research and the community led me to change my thermostat and temp sensor, which I did with oem units. it worked perfectly for a couple of months until I took the car off the road for about 1.5 years and brought it back on last september. She came off because I had bought another car, not because she was overheating.

 

In April, the problem started again, I talked to my shop and he replaced the T-stat again, problem didnt occur anymore, thought I got a faulty T-stat when I did the replacement. Back in June of this year, on the hottest day of the year, I blew a coolant line, specifically to my turbo. I had it towed home ,replaced it and burped the system. Seemed to be fine again. Then it started happening more and more frequently. Now sometimes it would hover at the high mark for longer than it did before. I realized if the revs were high, it would drop down. Specifically, If it was high, I would drop a gear, do a pull and it would just plummet to below the middle. I had thought that was really weird, but just took it as more evidence and kept monitoring. During all of this up until the last couple of weeks, besides the intermittent overheating, the car has felt fine. Pulled strong, held boost no problems, same gas mileage, nothing else telling me something was wrong.

 

Some other things ive noticed are that my coolant overflow would boil over and spray coolant all over the underside of my hood. I would top it off so as to not run out, and it would blow it all out so I now keep it low in the overflow tank but still make sure there is some in there. I have checked in the tank, and seen, idk if it is steam from boiling coolant or exhaust gas, but when I smell it, it smells sweet like coolant but a slight hint of something else i cant put my finger on, could be exhaust gas. A couple of weeks ago, making a pass on the highway in 5th from 75-85, there was a stutter in the car and then it went fine, got a code for P0244, wastegate solenoid performance. That has only happened twice, mainly cus I avoided 5th gear passes under boost.

 

After this week, now I am worried. When I hit boost merging on to the highway, the car stuttered a bit, it overboosted slightly to ~13-14 psi from normal of 11 and the boost would flutter heavily. Then I got a CEL for P0301, cyl 1 misfire, and PFFFF and PFFFE from my accessport. Reset the codes and drove it gingerly. Then this morning, I accidently forgot, hit boost, maybe about 30% throttle at most and the same thing happened.

 

Some of the testing I have tried include I burped the system after I noticed it had been boiling over everywhere. I did do the coolant exhaust leak test. I did the test 4 times, and the fluid never changed colors, I believe this to be because the problem isn't constant. I even tried doing the test on the coolant overflow to see if the the vapor was steam or exhaust gas. I gave it an oil change, there was no coolant or metal or anything odd whatsoever, matter of fact the oil looked really good. I was advised to run a compression test. I tried to do it myself but didnt have the capabilities, mainly the space and time. Talked to my local shop who does most of the average car stuff for me, he said not to have him do it, have the shop who would do the repair work so I dont pay for the test twice. So the compression test hasnt been done yet.

 

All of the things I have thought it to be are a bad radiator?, nah coolant flows fine and is clean. I also have no shortage of heat for the aircon. Fans dont work?, nope, I hear them working all of the time, especially when the car is trying to overheat. Since I could get the temperature down with a pull, maybe the waterpump? I was thinking the higher revs would spin the pump faster and move more coolant through the system. Idk still could be a possibility. Timing belt and everything was replaced at 106k. Now that I am getting a cyl 1 misfire at boost, Im thinking there is in fact a hg leak, in cylinder 1 and the its a small one thats getting worse and the boost is causing the leak to expand thus the boost issue, i.e overboosting and fluttering.

 

Another thing I am worried about is since the car has gotten hot a good amount of times, but never actually overheated, could my heads have been warped? If they are warped and/or there is a hg leak, when does it make more sense to machine and fix the current engine, replace the engine entirely or junk the car?

 

So yeah, thats my problem, dont know whats going on and I cant get a solid answer as it doesnt seem to follow any standard failure signs. Do you guys have any insight or leads? Anything is appreciated. Thanks

Edited November 9, 2021 by Benjewman

[Pleides]

An aluminum block and multiple overheating incidents? You'd be lucky to not have a warped head or head gasket. Those coolant turkey baster block tester fluid color change tests can be fooled with leaks still. My Honda blew a head gasket after the thermostat got closed for maybe 30 seconds. I'd imagine you're probably in for a big repair bill. I'd assume you have an external head gasket leak. That's how most Subarus go, not with oil and coolant creating a nice cocktail together.

 

The plastic end tanks in the radiators tend to fail on these cars. That said, anything over 220F sustained on these cars can do damage, so I'd be doing a compression and leakdown test first.

[Max Capacity]

Just asking, have you replaced both radiator caps ? My wagon gave me some concern a few weeks back with coolant levels in the overflow bottle.

 

Since replacing both caps. (I used the NAPA cap for the turbo tank). No more issues.

 

You can let your idle and watch to make sure the fans cycle after a few minutes. It may take 10 minutes. Make sure they work when the car is parked.

 

But I also agree you may need to do that color test, as you have lot's of higher heat in the block.

[All_talk]

My vote is bad radiator, but you may now have other issues from the repeated overheating.

 

The rad can look fine from the outside with no external leaks and still be bad. It is common with Subaru's for the tubes in the rad to plug. To check this, bring the car up to temp, make sure the thermostat in open and let it run for a bit. Shut it down and feel the radiator core top to bottom (reach through the fans or pull them first). If you find sections that are cold or much cooler than the rest the rad is bad.

 

First check for bad head gaskets is bubbles in the recovery tank.

 

Gary

[Benjewman]

So maybe the bad radiator could be the problem. And then raising the revs sent more fluid though the system and overpowered the block in the radiator?

 

If that's the case, could my cyl 1 misfire now be because of constant overheating and now my heads are in fact warped?

 

I have seen bubbles in the overflow tank but I thought it might be been boiling from the overheated coolant.

 

I will try to check the radiator though.

[Pleides]

If you're getting misfires consistently then just replacing the radiator almost certainly won't solve your problem. Yes, you could very likely have warped your heads or broken up a valve from prolonged overheating.

 

The radiator would be easy to replace with the engine out of the car for a head gasket replacement. I wouldn't throw a new radiator at the car until you're 100% certain your vital engine parts are in good shape.

 

Bubbles in your coolant overflow mean there's an appreciable amount of air or pressure from exhaust gases making its way into the coolant. Since you managed to not see a change in color with the block tester fluid, I'd check around the perimeter of the heads for leaks. Might be easy to spot, might not be, but that's usually how Subaru HGs fail. Also totally possible you have a little air getting in from a coolant leak elsewhere given how old our cars are now.

[Benjewman]

I just got home rom driving home from work. I tried feeling the radiator the best I could through the fans. I'll admit it probably wasnt the best feeling but going up and down a couple of times, it seemed to feel the same temp, if anything slightly cooler towards the top.

 

The idea of the radiator being faulty seems to make sense with most of the symptoms ive been experiencing. Is there a better, more sure fire way to check the radiator with out removing from the car?

 

 

 

I was under my car recently to do an oil change and I also had to change my power steering pump. While I was under there, I chcked for leaks of any kind, oil cooolant what have you, I couldnt see anything that I know of. Ive also been monitoring regularly from up top and dont see any visible leaks either.

[Rusty9]

Are your fans actually working?

 

-Check fan operation (detailed instructions/troubleshooting in FSM

-replace caps (2 different caps, make sure they are in the correct locations, inexpensive and easy to change)

-check for pinhole leaks (UV dye)

-check water pump (vanes can erode from cavitation, no flow at low rpm)

-check that "jiggle" pin is in the correct orientation on t-stat. (up)

-replace radiator (inexpensive and easy to change)

[Benjewman]

Are your fans actually working?

 

-Check fan operation (detailed instructions/troubleshooting in FSM

-replace caps (2 different caps, make sure they are in the correct locations, inexpensive and easy to change)

-check for pinhole leaks (UV dye)

-check water pump (vanes can erode from cavitation, no flow at low rpm)

-check that "jiggle" pin is in the correct orientation on t-stat. (up)

-replace radiator (inexpensive and easy to change)

 

Just Curious,

 

How does changing the caps help if it seems the system is properly pressurized?

 

The fans do work as they are supposed to. When I was running the fluid test, they came on a couple of times. I can also hear them when I'm driving and I can hear it echoing off of something so the fnas arent the problem.

 

UV Die test? How do I conduct that? Im assuming put it in the coolant, drive and then search with an ultraviolet light?

 

A shop replaced the most recent T-stat so I'd assume he installed it properly. Also dont have the time to start pulling coolant lines and dealing with all of that. I have an unbelievable amount of personal stuff happening all at once.

 

The radiator seems like a sensible fix, lining up with the sympstoms I have but I checked last night and didnt feel any cool zones. Do you have any other methods to test the radiator. Also I agree with the dude above you that even if it is the radiator, Im not replacing it until I know whats going inside the engine now with misfires.

[Rusty9]

well, a cap may hold pressure, but not the correct pressure. I think the manual states 12 psi as the lower limit for replacement, 14-18 psi being ok. If it only holds 10-12 psi (or less) then your coolant will boil. Most cooling systems testers available for rent at auto parts stores can test this, but caps are like $7

 

UV dye is added to the coolant, just like you imagine and then you drive around for a day or two and then inspect every hose, fitting, clamp, radiator with UV flashlight. Some pin hole leaks are so small the heat from the engine bay evaporates any wetness you might see without the UV dye.

 

You'd be surprised at how many brand new t-stats I've pulled with the jiggle pin at the bottom. not the end of the world but it can make burping the system take forever.

 

Only other test for radiator is pressure tester, but that won't detect a clog like feeling for cold/cooler spots or inspecting with an IR thermometer or camera.

[Benjewman]

Gotchya, yea that makes sense. Ill for sure look into those two tests. Worst case scenario its 40 bucks gone. I also have my sister bringing me her ir thermometer so ill be able to get a better reading of that and report back to you guys.

[Infosecdad]

Was it an OEM thermostat? It's fairly well documented around here where many aftermarket thermostats fail quite quickly.