I just bought an s4 with a blown engine. The first engine I swapped into the car appears to have a blown coolant seal. The engine runs great but it overheats in about 15 miles. It doesn't matter if I just cruise around or run it at redline. The temp gauge stays fairly stable for the first few miles and then jumps up to the line just before the red zone. When I stop the coolant is bubbling/boiling, the radiator hoses are so hot you can just barely touch them, the radiator is very hot on the passenger side (where the hoses are) and almost cold on the drivers side. The radiator temp is what really has me confused. I originally thought I had a bad radiator and changed that but still have the same results. I don't really understand what is happening when the coolant seal goes but my guess is that exhaust gases are getting pumped into the cooling system. That explains the super hot hoses but whats going on with the radiator? Do I have two problems here? What are the chances of having two radiators that have a flow problem? One of the radiators has a cap on it and I have confirmed the water pump is working. Am I missing something? I am picking up another engine on Friday that was supposed to be a spare, but I'm feeling that I am swapping another engine. Hey at least I'll be good at it now. Two swaps in two weeks! Any thoughts are appreciated.

Chuck

 

Ever checked the thermostat? Any air in the system? properly bled? Take the cap off the rad when its cold of course have a look in there with a flashlight drain a little coolant if necessary see if the rads all clogged up, although i highly doubt it.

 

I first thought I had a bad T-Stat so I yanked it and drove without it. Same problem. Tested T-Stat in boiling water and it does open, so that wasn't the problem. I also heard that driving rotary's without T-Stat is something they don't like, not sure if thats true but I did not see any difference in overheating issue. As far as air in system that was another thing I thought I had because the heater would blow cold/cooler air sometimes. Finally I did a pressure test and the system leaked but no signs of any leaks/coolant in the engine bay. I had someone else start the car and could smell anti freeze in exhaust, so I'm fairly confident I have a blown coolant seal. The weird thing to me is the temp difference from side to side on the radiator. I have a contact type infrared themometer and one time when I checked the radiator it was 100C on passenger side and 30C on drivers side. Thats when I thought I had a cloged radiator and changed it. I have an electric fan and I even flipped it around so the temp sensor was on the hot side of the radiator but it made little to no difference. My plan is to change the engine again, but I am concerned I still have a cooling system problem. Is there a special trick to bleeding air? The directions I have say to fill at the gooseneck with the bleed screw out. Once coolant comes out of bleed screw put screw back in and top off at gooseneck. Is there something else? The other thing I read somewhere was that if you have two pressure caps (which I do, 1 on gooseneck, 1 on radiator) that does bad things and that one cap should be just a flat cap (non-pressure) but I don't see how that would make a difference. The car that I got the donor engine from had the two caps. From the other posts I have read it seems that the needle for most people stays about 1/4 - 1/3 on the gauge, does this sound right? I'm itching to get to really drive the car, it handles great and even with a messed up engine it seemed plenty powerfull. I've got a track day coming up in mid-November that I hope I can get to.

Thanks, Chuck

 

If the temp accross the rad is uneven, then it is probably clogged.

 

i have the same problem the top of the radiator is cool and the temps allways in the cool (it works) and i overheat i thought the pump was out so i pulled it the pump turned out ok i was told that mabey to much rust in the passegas so i put cleaner in there still same results oh ya it will blow the hoses to pieces when i floor it its driving me insane i just got the trash on the pass. side the way i like it