Hey Guys, I too recently purchased the mishimoto radiator with new gimmick hoses and 160 degree thermostat 1 month ago and almost immediately had over heating issues. After weeks of burping, filling and overheating, due to low radiator fluid I said enough is enough. I decided to go through the total cooling system to determine the problem. I had the radiator installed by a certified mechanic and he to was frustrated with the reoccurring problem. So, we took a whole day and tried to diagnose the problem. Note, the car never overheated with the stock radiator and was only upgraded to better help cool the car in its new Florida home. Car is now blowing coolant out of the radiator filler cap.
List of procedures we tried:
1.Mishimoto radiator came with a 1.1bar cap and I replaced with a 1.3bar-Same problem
2.I pulled the 160 thermostat and replaced it with the stock 180- Same problem and worse
3. Heated both thermostats on the stove in water with temperature gauge-both worked perfect
4. Flushed the whole system and refilled with new fluid/ drain petcock worked great and flow was steady-Same problem
5. Checked the fans-Working perfect
6. Checked the radiator for cold spots while car is off and at operating temperature-None could be felt
7. Checked the radiator with a laser heat gun- All readings from left to right normal 155 on drivers side and 180 on passengers side. Mishimoto verified this to be normal
8.Checked for any leaks-1bar no leaks 1.5bar it would leak at the filler tube on the compression tester fitting. Tried several different fittings and was able to push 2bars with no leaking-System air tight
9. Co2 chemical test for exhaust fumes in coolant system-Clear
10. Checked oil for antifreeze-None
11. Checked antifreeze for any contaminates-None
12. Removed upper hose and ran to confirm water pump was working-Working great and had great flow
13. Contacted mishimoto. Was asked to email everything we tried, tech was out. No response as of 10/4 but only emailed them on 10/31 and would assume the tech would be out until 10/5 and hope to get a response soon after.
14. Switched the upper radiator cap on the filler box with the radiator cap on the radiator-NO PROBLEMS AFTER 4 DAYS AND 200 MILES OF SPIRITED DRIVING TO TRY AND CAUSE OVERHEATING!
Next step was to pull the radiator and reinstall the stock radiator to see if the radiator was somehow bad. Radiators in all respects are very simple and with no radiator fin damage, leaks or blockage it is unlikely to fail or have problems. Blockage would have been the only answer and I am not going to flow test a new radiator to determine adequate flow. I will let mishimoto replace the radiator and test it for that issue.
So far the conclusion is that the 3rd radiator cap tried worked well or that the upper and lower combination of radiator caps worked. I no longer have coolant blow off and in return the coolant level is staying consistent and has been checked after each drive and every morning with no further overheating. Will try and keep everyone updated and hope this will help you with any of your radiator problems.
I highly recommend installing an aftermarket temperature gauge with a warning to make sure that the overheating does not cause engine damage. I did this immediately after it overheated the first time. The stock gauge works well but is hard to monitor going down the road and you will not see the 20 degree ups and downs that happen very quickly. The temp warning on the aftermarket gauge can be set to give you amble time to pull over and let the car cool down. Hope this helps!