Ok so I have a 95 eclipse rst and im having the hardest time tracking down an overheating issue. I can start the car and drive it for about fifteen min with the coolant temp gauge reading normal but after this no matter if im sitting or moving the ect will start to rise to about 3/4 temp with both fans running. The problem seems to get better when I coast or keep the rpms low and stay away from boosting. I have installed a new water pump, thermostat, rad. cap, rad. hoses. Also I have dont a cylinder leakdown test that showed 10% 10% 20% 10%, I checked this before and the readings are the same as before. everything is leading me to believe headgasket issues but since I did the leakdown test and there is no oil in my coolant or vice versa im doubting this. Any help or comments would be appreciated.

Have you checked out the Coolant Temp Sensor yet? I believe it can be tested. If not, since you've already replaced everything else, maybe that is at fault. I would check out the wiring too just to be safe.

How about your radiator & heater core? Sure you don't have a clog? Both bottom and top hose hot at full temp?

EDIT: Is there anything blocking the radiator at all? Trash, paper, etc...

You need to verify that the gauge and sending unit are reading correctly. Get an IR temp sensor or another means to verify the physical temperature of the coolant, before you spend any more money on replacing parts. If the Gauge sending unit is off, the gauge will reflect an incorrect reading - not that the gauge tells you much useful information to begin with without numbers. If the ECT sensor is off, it will not give the correct temp. to the ECU and the fans will not trigger appropriately.

Both sensors have been replaced. Looking at pid data on a scan tool ect is as high as 220. Both the instrument cluster gauge and ect sensor agree that its overheating. No trash or debris in front of radiator. Big front mount infront of it but my problem just started so highly doubting that's the issue

Do you have the fans going the right direction? Alsohave you tried cleaning the radiator with soap and water, iveseenthe fins get dirt in them and not cool. Last step, is it an oem radiator? No matter what I did after I put my hahn fmic on it would overheat when driving. If all that checks out the we can assume either a hg or worse.

Rad is fairly clean only a few bugs and stuff. It is a stock rad but I've been running it for months prior with no significant problems.

Its getting to be summer time though.

I've drove it on days much hotter then what it is now with no problems. Even the other night it was 60 degrees or so out at like 12 midnight with a nice breeze and it still overheats. I see what you guys are saying but its not a rad problem, I'm 95 percent sure. I'm going to do a block test, compression, and another leakdown test tom morning. I just want to see some bad results so I can end this problem.

They sell hydrocarbon test kits. Might be worth checking into.

My car did the same thing after swapping to MS. Mine came down to voltage tho. Under any acceleration, my voltage would increase resulting in the temp. gauge to rise. Best bet is as stated, get a coolant gauge to monitor it. I purchased a cheap sunpro one from autozone. Read correct all the time.

Block test, comp check, and leakdown tomorrow. Def getting a coolant temp gauge ASAP and gana try some heat blankets and header wrap if I see good results on the other there test. I do have a volt gauge and haven't noticed anything out of the ordinary as of now. Might get creative with some ducting to the rad and stuff too. Ill keep you guys posted. Thanks

The headgasket can blow without any mixing of coolant. You have a blown headgasket.

shes gana be ok. Today I actually took time to think out my problem and I am 99 percent sure I've found it. I got out the inferred thermometer and checked all my hoses when my temp gauge was reading three quarter temp, found 185 to 200 on all hoses except the coolant crossover pipe right above the exhaust manifold... This crossover pipe read 240! this pipe dumps directly into the thermostat housing and also right to both the ect sensor and sensor that goes to the gauge cluster. So what I'm trying to say is a very good heat shield is being made tom to shield this hose from the 700 deg. Temps coming off the log style turbo manifold. makes sense that under boost and while even on the gas ect temps go through the roof. Ill make that shield and let you guys know if I'm right with my diag.