Hello,
My '01 3.8 overheats after a short time running at idle and after a few miles. I had an overheating event from coolant loss due to heater core leak. Leak was repaired and but continues to overheat. Fans are ok, waterpump is ok, thermostat is ok. Appears to be oil in coolant. Will run ok on highway but of course in city traffick will overheat. Any help with diagnosis would be appreciated. Thanks.

 

You said the fans are ok yet you describe a fan issue perfectly. How did you test the fans?

 

Did you purge the air out of the system? There is a little brass air bleeder screw on the top of the T-stat housing. Find a spot to aim the car slightly nose up, fill the rad, fill the overflow and run the engine at idle. When it gets hot open the valve and let the air out. It may take a couple times to get it all out so dont think that the first time you get coolant out of the bleeder that you are done.

Also my 3.8 always looked like it had coolant in the rad and I dont know why as the cooling system does not pass through any oiling systems of the engine. I thought trans fluid so I had a trans shop check the lines and there was no pressure lost in my trans cooling lines. I chalked it up to dirty hands or a drip or drop that go in while I had the engine out.

Massey

 

Most of the time when someone complains of oil in the coolant it ends up being left over Dexcool. Even flushing can miss some.

 

I bypassed the relays so I could maually activate the fans.
Regarding the purging, I thought I was done after the first time the coolant started coming out of the bleeder. I will go through the process again. Thanks for your input. Also, regarding the comment I made about oil in the coolant, I'm not absolutely positive it's oil. I should have said it appears to be oil. How can I determine if it is oil or not?

 

Like I said mine always looked like there was oil floating on the top. Dex cool mixed with other coolant can do that as well. It is not a big deal unless you are actually pumping oil into the water jackets. There is no place in this engine were pressurized oil gets near the cooling system except the trans cooler built into the rad. There are a couple places were you can get water into the oil but not the other way around.

Massey

 

I suggest anyone that works on cooling systems buy a Lisle funnel. It comes with a set of radiator adapters for most any car.

You attach it, fill the radiator and leave coolant in the funnel. As the engine warms air moves through the radiator and comes out the funnel. Once your done you put the supplied plug in the funnel and move the leftover to the tank.

I used the built in purge valve several times and still had air coming out the funnel.

here is a link to one on amazon. I actually got mine at Oreilly auto.

 

Those funnels work great and keep spillage from happening as the radiator "burps" the problem with the 3800 is the intake is higher up than the radiator is and the air gets trapped at the highest point and never leaves. Then it will build up pressure and not allow any water to pass by which will cause overheating. Small amounts of air will get caught in the stream of water flow and move to the radiator which is the bubbles you get after the large ammount of air has been purged. This air would normally have been purged by the radiator cap and sent into the overflow bottle.

Using these funnels is a great idea as they help prevent the spillage while filling and the inital burping of the system but with any engine where the intake is higher than the radiator make sure you also purge the air from ALL valves. (the 3800 only has the one)

Massey

 

Massey,
Wasn't implying not to use the purge valve. Rather using both. Wouldn't want anyone to think the funnel replaces the purge valve. I just did a flush and even after having steady flow of coolant at the purge valve I still had air coming out the filler. Most likely small bubbles initially trapped in the radiator.

 

Have you felt your hoses that come off the engine headed to the heater core? Mine were completely blocked and it took some time and a coat hanger to unblock the lines. This was due to the Dexcoolant getting all gunked up and causing a lot of issues. You may also have a block in your radiator as well. You may want to not drive it in this condition till you figure out what is going on. You could do some serious harm if you overheat the engine and have some weak lower intake manifold gaskets. My 97 RS overheated, coolant and water flowed into the block which resulted in a chatosrophic failure. I had to find a new donor motor but still had the blocked hoses. I also ran a hose to the heater core, turned on my faucet and watched the mud flow for 10 minutes. My cooling system was completely gone. Sorry those are things that happened to me.