'02 300M overheating now

I did buy a new thermostat, gasket and hose, but decided to consult first with my has-worked-in-an-auto-shop neighbor (the one who declined to do the a/c job for me). He had me warm the engine up with the bleed valve open (with a tube to a bucket) and the coolant-bottle cap off and said, "Don't worry about the coolant that spews out: it's being forced out by the air burps." More than a gallon of coolant later (which I had to keep adding to maintain the correct level in the coolant tank) the temperature still rises too high, and I have no heat in the cabin (no a/c-related fault codes). He is now suggesting head-gasket failure, and I do see steam coming from the exhaust, but I don't know whether the amount is abnormal, as I don't usually stand behind my car and watch the exhaust. I see no sign of water in the oil.

My neighbor is going to try to borrow a compression tester and also plans to talk to his friend who now owns the auto shop where he (my neighbor) used to work; he is by all accounts a Chrysler fanatic and may have some useful insights.

Any words of wisdom from the assembled multitude here?

Perce

it is acting like your thermostat is stuck shut. try this first.....

let it cool down cold. Then with the coolant full, take the cap off and watch it while someone starts it up. if you see bubbles, see if you can find a parts stores that sells one time use "block testers" they stick down inside the coolant and change colors if there is exhaust gases in your coolant.

BUT....if you DON'T get any bubbles in the coolant when you start it up cold, then drain it, put in the new thermostat. Then refill it with the bleeder screw open and the hose connected to it. as soon as you get coolant out of it, then close it and fill the coolant the rest of the way.

My neighbor said that the sudden rush of coolant from the bottle showed that the thermostat had opened -- but I wasn't sure that I believed him.

I haven't seen bubbles in the coolant: it stays clear and bubble-free until it gets almost up to half-scale on the temp. gauge, at which point the "burps" start.

Perce

does it overheat just idling in the garage?

or only driving down the road?

>

I haven't left it *merely* idling in the garage: I've sometimes held the gas pedal down a little to get it to warm up faster after following the bleeding procedure -- to see if the temp. still goes too high, and it does.

I've driven it slowly (25mph max., probably) around our subdivision -- difficult to say how far -- and the temp. gauge has been in the red by the time I got back home.

Perce

>>

My neighbor came back after talking to his friend the Chrysler fan and new owner of the auto shop. He says "Definitely not the thermostat: these things are pain in the neck to bleed, and you just have to keep at it. But it could be that the vent hole in the thermostat housing is blocked." But if I have to remove the thermostat housing to check whether that hole is blocked, I might as well replace the thermostat anyway.

Perce

>>

And my neighbor said that his friend the Chrysler fan and new owner of the auto shop told him that he had sometimes had to drill extra holes in the body (the flange, I assume) of the thermostat to deal with the airlock problem. Sounds flaky to me.

Perce

>>>

this is the 3.5L just like mine. only difference was mine was first gen.

never had any issues with the bleeding. filled it until coolant ran out that hose, with a small amount of coolant in the catch bucket to cover the end of the hose so it didn't suck any air in that way, once I got coolant out that hose, then fill the coolant tank the rest of the way to the full point.

if its overheating that fast, the upper hose is getting hot, and the lower one is not, and you are POSITIVE the thermostat is ok, then start looking at the water pump.

>>>>

well wait...........

does yours look like this?

if it does then your bleed valve is different than I thought it was....yours is probably behind the first couple intake runners.

>>>>>

The oil does need changing (just past the 3000 mile interval), and since some say that removing the oil filter makes it easier to get at the thermostat housing, I was planning to change the oil at the same time. But I see no signs of moisture on the dipstick.

At this point I am NOT sure that the thermostat is OK, despite what my neighbor and his buddy are saying.

The water pump should be OK, as it was replaced al> this is the 3.5L just like mine. only difference was mine was first gen. >

>>>>>

Yes, my thermostat housing looks like that. Here is a diagram (posted by somebody else) of my bleed valve location:

yeah that looks about right. the lower end of that hose goes in a bucket with a little bit of coolant in it. I use a clear hose so I can see it running out the hose.

if its plenty warm outside when you fire it up, and its not real humid, then you shouldn't be getting any whites puffs out the back.......especially when you give it light throttle. either way something has suddenly changed, sine it worked fine for a while after the A/C repair.

By the way...are the fans coming on? I ask because with the A/C off, and just idling in the driveway or garage, they should come on automatically at the right temp....hot enough and they will go from low to high. and ofcourse they should be running with the A/C on as well.

>>>>>>

It was raining and not particularly warm (60ish) yesterday when I noticed the steam from the exhaust.

My neighbor suggests that what changed was that the air bubble moved from a place where it didn't matter much to one where it does matter. Possible? I don't know. Could such an air bubble survive the specified bleeding process?

The fans are com> if its plenty warm outside when you fire it up, and its not real humid, then

>>>>>>>

I've just noticed in the service Manual the following:

"? When Engine is cold: Thermostat is closed, cool- ing system has no flow through the radiator. The coolant flows through the engine, heater core, coolant bottle and an internal engine by-pass. ? When Engine is warm: Thermostat is open, cool- ant flows through the radiator, heater core, coolant bottle and by-pass."

Note in paragraph 1 that the coolant is still supposed to be flowing through the heater core even when the thermostat is closed, so even if the engine isn't warm enough for the thermostat to have opened, shouldn't there be *some* heat in the cabin if I crank the temperature up?

there might be some but not really hot until it gets over 150 or so.....

I think that's the case for most cars that coolant always flows through the heater core regardless what the thermostat is doing.

I know that on my 300m that in the winter (when the car has been in the garage overnight with the garage temp at about 45 - 50 F and outside temp in the 10's or 20's) that if I turn the heat on, I will feel some luke-warm air after about 1 minute of driving - and the needle of the temp guage pointing to the first mark on the dial. After 2 or 3 minutes of driving, the air is blowing hot.

About 2 years ago I had the timing belt changed on my 300m - and along with that the water pump was changed too (no reason other than it was easy to do with not much added cost). I have the original pump (and belt). The new pump was made by Fenco.

I'd have to say that in your case - the pump must have failed. The impeller must be free-wheeling and not doing any pumping.

Ditto......

as long as he's not getting any bubbles in his coolant at cold, he's bled the system, and not getting any steam out the tailpipe or coolant in the oil, then I am aiming for the same thing.

Yuck! That's not going to be cheap to have someone fix. That's almost as much work as the timing-belt job I had done two or three years back -- although not as many parts now, of course. The water pump was replaced then; surely it should have lasted longer than this.

But that would explain the sudden onset of overheating when it had been running fine after the a/c job.

I tried to get at the thermostat today but couldn't release the spring hose clamp. I've bled the thing again (cold) and kept pumping the top radiator hose, which seemed to get rid of still more air -- coolant bottle fluid level dropping even with the bleed valve closed. Since using the "special tool" filler funnel (which I don't have) according to the manual releases a small amount of coolant into the overflow chamber, I let some coolant flow into it before I started the engine.

I then ran it for about 15 minutes at engine speeds between 500 and

2000rpm, and it was just getting up toward the red (rather sudden increase from sitting around half-scale). The coolant level in the overflow compartment of the bottle was higher then.

Still no heat in the cabin.

BTW, I read somewhere today that modern thermostats rarely stick closed: they are designed to fail > Ditto......