Mystery overheating problem.

[oh34v6]

I knew that my water pump was on its last leg as I was losing a considerable amount of coolant every few months. It started running warm last week just a few weeks after topping it off with antifreeze, so I figured it was time to do something about it. Topped it off again, and drove it to my dad's on friday to take care of the problem. About 5 miles away from getting there, I loose almost all coolant and it starts running around 260. I shut it off for a while to cool down then limp it the rest of the way. Its a 3.4l, so the powersteering pump was in the f'n way so the job took longer than I expect. I had to leave for work and my dad finished putting it back together for me.

I came back the next day, he said he had put back together and it was holding water and temp just fine. Said he took it around the block though and thought it had a misfire. It had been running just fine before though so I took it for a test drive. Got about a 1/10th mile down the road and knew exactly what was wrong. He put the 4 and 6 cylinder plug wires on the wrong coils. Take it back, switch wires around, and it runs just fine.

Run it a mile down the road on my way home before it start overheating again. I turn it around assuming the thermo stuck shut. Take the thermo out, it had a piece of gasket maker stuck in it from replacing the water pump, but I replaced it anyways cause they're so damn cheap. Take it down the road again, and still overheating. So I flush the entire cooling system thinking I have an air bubble, yet take it around the block to overheat yet again.

I'm ****ing stuck now. I have no clue what is going on. I took the thermostat out again just to make sure i put it in the right way(didn't really thing i didn't, just double checking for brain farts), and the upper LIM was bone dry! This worried me that I had a gasket go bad, but on checking the oil it looked perfectly fine. Where the hell did all that coolant go!

Anyone have a clue what I could look for? Would overheating crack/warp a head or blow a head gasket, yet not let water into the oil? I really don't know what to think right now, I'm so pissed that something so easy has turned out to have so many grimlins.

BTW, radiator is only like 2 years old, so I don't think that would be clogged. And I have always ran green prestone antifreeze since i've owned the car, so i doubt its because of the old dexcool related problems either.

Thanks for any help.

[nascar24jd]

Re: Mystery overheating problem.

It is normal for the coolant level to drop after a repair like that. Did it go bone dry, ir just low?

Is the belt routed properly around the water pump?

If there is no coolant in the oil, no coolant in the exhaust, no misfire, then it should not be a head gasket issue.

I also have a 3.4L, and they typically do not get air-bound. After you top it off you should let it idle with the radiator cap off. When it reaches full operating temp the t-stat will open and the level will drop. At that point, you should fill the radiator all the way to the top and put the cap back on.

Speaking of cap, is your's good? A bad cap will cause the coolant to escape into the overflow bottle.

Are there any external leaks?

Is the passenger side carpet wet? (Heater Core)

Do you smell anti-freeze near or around the engine compartment?

Post your findings and I will try to help you more.

[TopHatJimmy]

Re: Mystery overheating problem.

My coolant system was giving me fits last winter/spring. Kept overheating. I replaced the thermostat twice, but didn't help.

You can check your thermostats by taking them out of the car and putting them in a pot of water on the stove. Set the burner to high and watch to see if the t-stat pops open.

Mine did. Explains why the t-stats didn't fix the problem.

I think mine was just gunked up and I had a blockage in the radiator someplace. I drained all the coolant, filled it up with water and hit the freeway for a few miles, came home and drained the radiator. I did this like 5 times, and got nasty crap draining out each time. Then took off the lower radiator hose and stuck a garden hose in the filler neck and turned the faucet all the way up to blow out the radiator.

Haven't had any problems since.

[oh34v6]

Re: Mystery overheating problem.

It is normal for the coolant level to drop after a repair like that. Did it go bone dry, ir just low?

Is the belt routed properly around the water pump?

If there is no coolant in the oil, no coolant in the exhaust, no misfire, then it should not be a head gasket issue.

I also have a 3.4L, and they typically do not get air-bound. After you top it off you should let it idle with the radiator cap off. When it reaches full operating temp the t-stat will open and the level will drop. At that point, you should fill the radiator all the way to the top and put the cap back on.

Speaking of cap, is your's good? A bad cap will cause the coolant to escape into the overflow bottle.

Are there any external leaks?

Is the passenger side carpet wet? (Heater Core)

Do you smell anti-freeze near or around the engine compartment?

Post your findings and I will try to help you more.

Manifold is bone dry. There was no trace of water in the upper hose either when i removed the thermostat.

Belt is good. Was one of the first things I checked.

No external leaks, no puddles, heater core seems fine. Doesn't smell like anti-freeze inside or out.

I'm pretty sure I was topping it off after the thermo popped, but I'll go pick up a new radiator cap tomorrow and double check that.

One thing that I notice also was that I could hear water boiling and bubbling in the overflow after it would start to overheat, and it appeared that water had been forced out of the overflow cap. Does this sound like a bad radiator cap?

Thanks for the help guys.

[nascar24jd]

Re: Mystery overheating problem.

It could be a bad cap, the only part I really don't like is that the manifold is bone dry.

Try the cap as it is inexpensive. The see what happens.

[cam98aro]

Re: Mystery overheating problem.

It could be a bad cap, the only part I really don't like is that the manifold is bone dry.

Try the cap as it is inexpensive. The see what happens.

yeah that sounds bad

he is going to be very lucky if his block/heads arent cracked from running it like that.

[oh34v6]

Re: Mystery overheating problem.

I was thinking too that some warping or cracking might be going on, but with no coolant in the oil it seems unlikely. Its not a big deal even if it did, I have a block and some 3400 heads sitting around waiting for a chance for something to be done with them. I just want to figure out what is causing the problem before i put a new engine in and end up with the same problem.

[cam98aro]

Re: Mystery overheating problem.

I was thinking too that some warping or cracking might be going on, but with no coolant in the oil it seems unlikely. Its not a big deal even if it did, I have a block and some 3400 heads sitting around waiting for a chance for something to be done with them. I just want to figure out what is causing the problem before i put a new engine in and end up with the same problem.

well, go to the parts store and buy a pressure tester, that will tell you if something is wrong, or if the cap is bad and spewing your coolant out

[oh34v6]

Re: Mystery overheating problem.

Just pulled the car out of storage this week. New engine isn't quite ready yet, start a new job in two weeks, and I don't trust the 2.7l in my Intrepid to travel 70 miles every day. The car will run just fine if I top off the radiator, start car, wait for it to warm up and pop the thermostat, and top off again. I've done this and drove 30+ miles without any overheating problems, but if i let the car cool off and just jump in and go its maxing the gauge within a few blocks. I have a spare set of heads that were on my donor motor, so I ordered head and intake manifold gaskets and I'm gonna tear it down and replace all of those. If I notice anything wrong with either of the heads I'll just replace those too. I might just put on my pacesetter's now to instead of waiting for the new engine to be done.:naughty:

The only thing that I'm confused about is that after driving it a good amount there still is no sign of water in the oil, but I did find a chocolate-milky sludge in my intake elbow. No sign of it anywhere else, not in filter nor tb/uim. PCV valve?