I've got a number of tuning questions but first, the car is overheating. My car is finally finished. I got it back two weeks ago. The engine is an MMS aluminum block 427. Last week with about 400 miles on the engine it started getting hot. This was after 3-4 hours of 50-60MPH back roads, some stop and go traffic and some highway miles. The odd thing was that it didn't get hot until I stopped for about 15 minutes before going out again. When it got hot (needle went just past 210 which appears to be about 230 via autotap) I flipped on the heater and it went right down. I pulled over at the next exit and as soon as I stopped moving the needle went back up. I shut it off and watched it keep going up to about 245 (I've got an idea of how the temperatur gauge works now after a few hours of atap). I left the heater on (in georgia heat ) and started it a couple times for a few seconds to pump more water into the heater core. It cooled off quick and stayed at the 210 line until I got home. Then I hit the ls1 boards.

The first thing I did was pull the FTRA. I thought the big cubes might require more airflow. That didn't change anything except how quickly it cooled back off once I was at highway speed. Next, I bled the coolant system. I let it run for an hour in the garage with the cap off and kept adding dex & water. I was getting bubbles then but I thought it was just air in the system. When I was done I drove it for about three hours with the air on max in stop and go traffic and the temp never went above 205 (watching atap). This morning I went out and took off the cap and there was a vacume in the radiator. Is that normal? I let it run again for about 15 minute and added coolant again. It took about two quarts and there were still bubbles coming up in the coolant. The reservoir was at the same level it was the day before. I drove it about an hour and it heated up again. I drove it home with the heater on again and it now sits in the garage.

My first question is, should I have just left the cap on? Did I introduce air into the system by opening the cap again today? Second question is, should there be ANY bubbles in the coolant? The lines all look fine, the thermostat appears to be opening and the fans both work and are running in the right direction. I even left both fans on at one point with the SLP fan switch. The fans are set at 175/165 and 185/175. The thermostat is (supposed to be) a 160 stat.

The next few things on my list are replace the cap, test the stat, check the plugs, and do a compression test. I fear a blown head gasket but with only 500 miles on the engine (and 3200 miles on the rest of the car) I'm having a hard time believing it could be a head gasket or anything mechanical for that matter... I don't hear a belt slipping. It doesn't leak any coolant. I don't see any white smoke. Aside from the overheating the engine/car runs great. I'm getting zero knock retard and don't hear any detonation even when it's hot (02s are at 950-990 at WOT and my ltrims are between -3 and 0 when I'm cruising). I'm really baffled but I'm fearing it's the head gasket.

Anyway, TIA for any suggestions.

 

Sorry to hear you are having problems with your new motor. The plan of attack you listed sounds like a good one. I would do a compression or a leak down test first. You have to pull the plugs out to do this, so you can take a look at them when they come out.

If this comes back OK, then start going back down your list of ideas. There should be no reason you still have air in the line after all you have done.

The best way I have found to get the air out on a F-body is to keep the line going to the coolant crossover on the front of the cylinder head off. Keep adding coolant to the radiator under you see a steady stream of coolant coming out of the crossover tube.

Jason

 

If all that comes to no avail then you can do a CO test on the cooling system. There a tester called a CO tester, a special tester that checks for the presense of carbon monoxide in the cooling system. Found many difficult head gasket/motor problems with this tool.All it is is a multi-chambered piece with a sqeeze bulb at the top. Then it has a special dye in the chambers. You pull air from the colling system of a hot/running engine & it will pass or fail.

 

Well, I ordered the felpro head gaskets. Seems to be a lot of problems with the comtek... I'm getting the leak down test done and coolant pressure tested tomorrow but preparing for the worst. Hopefully there's no problems with the head now. I'll let you all know how it works out.