Hello everyone, I just signed up to the forum.

I have a '99 LHS (3.5 v6). About 2 years ago, my water pump locked up causing my timing belt to melt over time until it snapped. It was pretty bad damage. I had to replace the starter, tensioner pulley, crank sprocket, water pump, thermostat, all belts, 3 exhaust valves on the left head and have it shaved off since it was warped. The car was running great, getting great gas mileage however i was experiencing some cooling/heating issues.

During winter, it would never get hot unless I came to a stop and let the car idle for a while. During summer (now), the car has been running hot. Finally it gave out on me last wk, overheated and started "clicking". Before taking the engine apart, I did some tests: good compression on each cylinder 150psi+, max of 13% loss on the leak test, oil on most of the plugs.

I took the heads to a shop to get them checked. They did a compression and a vacuum check; found out that some of the valve seats were leaking. Afterwards, they saw a few chips on the lobes of the right cam so replaced it. They also put all new valve seats and fixed 4 of the guides that were loose. I replaced the water pump and tested the thermostat, which seemed to be working fine. I also saw that 1/8" of the timing belt was literally shaved off on the outside perimeter; I have no idea what caused it.

Anyways, before I start putting the car back together, I'm trying to figure out the cooling/heating problem. I'd hate to put it back together and break down again. I'd appreciate any help.

 

"During winter, it would never get hot unless I came to a stop and let the car idle for a while. During summer (now), the car has been running hot."

That makes me think the thermostat may be stuck in a slightly open position.

 

I tested out the thermostat. It opened @ 180 and closed when I cooled it down.

 

Then I'm out of ideas. The thermostat is the only thing I can think of that can affect both heating up and cooling down. It might be worth another look. Once, many years ago, I put a thermostat in a little crooked and bolted the housing down on it rather than around it. Needless to say, it bent and ruined the thermostat.

 

If you have tried everything else and you are still having overheating problems you might have a bad head gasket. I didn't see what type of vehicle you were working on. I had a 1988 Dodge Caravan. I replaced everything in the cooling system including putting an oversized radiator in. The problem turned out to be a bad head gasket. I never observed any oil in the radiator.

 

Slice40Might be closer to your problem.

My 300C has and Elec. Type It had no heating problem but several month ago I had it When I went to the stealership they replaced the sensor and the blades they say that there is more efficiant blades for gulf and my sinsore was not giving the correct speed to motors

 

It sounds that air is trapped in the cooling system maybe because a blown head gasket. In some engines to get rid of this air you start the engine without the radiator cap ( make sure is cold before you remove the cap). As it gets hot you can get the air out by reving the engine up until no more air comes out.

 

I think there may be multiple problems with this. I don't see how the engine cannot get warm in the winter unless the thermostat is open or the coolant is low.

My first thought was coolant low and/or not flowing properly (ie air in system). The trouble with that thought is that the car should overheat in either case, summer or winter and 99lhschatt is claiming it does not in the winter months.

If the fans are not functioning properly or not at all, that could possible cause the overheat during summer, but there should be no effect on heating in the winter. Their function is to cool the engine down, not heat it up.

I can state from personal experience that the 3.5l V-6 engine is a bitch to bleed, especially without the special Miller tool recommended. I had a lot of trouble with that after rebuilding one. I ended up running it for several months without a t-stat and that solved the overheating problem, but the emmissions were off because the operating temperature was too low. Put the t-stat back in last weekend and finally got it to bleed out and not overheat. Not you daddy's engines in these though and special attention is required to get All of the air out of the system. That all being said, that in of itself can't be 99lhschatt's problem because it would overheat all of the time, and in pretty short order.

 

It wouldn't surprise me at all if the water pump failed in 2 years.

Before you go back together with it, put some new o-rings BEHIND the timing cover. The aluminum shell that bolts to the block.

Did you ever check your cooling fans???