My engine temp has been going whacko lately and i cant figure it out.

When driving my temp goes up, especially under a load (such as a hill).
It will climb up to the A or just below L in "NORMAL". It stays there for a bit, then drops down to "R" after the thermostat opens.

The weird thing is, when i come to a stop. The temp comes down.

So far i have flushed/changed fluid, thermostat, temp sending unit, and guage sending unit.

Is this a sign of water pump going out? I dont know what else to check..

 

Sounds like a air lock somewhere. Had the same thing with a Lebaron. Finally
fixed it when I back flushed the heated core.

 

Thanks for the reply.

I have read a few different times that backflushing is a bad thing. Would an air lock cause my exact symptoms tho? I am willing to try anything.

 

Could be an air pocket.... Almost sounds like a blown head gasket or a cracked head however..... Could be just a bad T'stat.... Try changing that first...

Try this however. When the engine is stone cold, open the rad cap and start the engine. Look in the rad and if you see bubbles, then you might have one of the above problems. If you see no bubbles, just let the engine warm up normally and wait for the stat to open. Keep the cap handy in case it decides to gush out on you....

Once you get the stat to open, bring up the revs on the engine some and that should start to get a good flow of coolant going. Do this for several minutes and if you have any air pockets, that should get rid of them.... What you are doing is allowing the system to flow free, but build up zero pressure. It's the pressure that can keep an air pocket around if one is there from the start.

I've had one vehicle with blown head gaskets and one with a cracked head. Both of them had bubbles in the rad on a stone cold engine...... The temp would go really high and then the stat would open and then it would be ok as long as it was not under load.... Once you were under load, the temp would rise again. Also, the coolant would get real 'foamy' too.... Never had any oil in it that I could tell, and the oil never had any water in it that I could tell, but I didn't run either vehicle very long in that condition anyway....

Good luck!

Mitch

 

thanks Mitch!

I've been suspecting a blown head gasket too, i am just hoping that isnt what it is. I have done the cold start and have not seen any bubbles (good thing). What does happen is that the fluid level slowwwwwwwwwwly starts to rise and "bounce" up and down until it finally comes up and out of the top of the radiator cap. The whole time this happens i see no bubbles. Then, eventually, the level drops when the stat opens.
One other thing that i can mention is that when the engine is off, i get coolant filling up the overflow about 1-2 inches. I dont know what is causing that......except for excess pressure. When the engine is running, it uses that 1 inch back inside the radiator again.

Any ideas with that info?

 

I had a cracked head that caused the same thing. Drove me nuts. I spent alot of money on radiator, fan, stat, belts, and hoses before I pulled the heads to check for a blown headgasket. The head had a small crack that would only leak when the engine was under load and warmed up. When at idle, it was cool as can be. I could drive around town with no problem. Get out on the highway and interstate speed and the temp would start to rise.

Good Luck.

 

Thanks expy,

Are there any tests that i can have done that will tell me if the head gasket is going, or if the head is cracked? I dont have oil in the coolant or vice versa.
I am not blowing smoke or have bubbles in my radiator.

What does happen is that i have coolant going into the overflow tank, but not a lot of it.

What can i do? Have the radiator pressure checked and tested for transfer?
I need to figure this out before it causes major damage.

 

Tough call.

Like everyone else said, best case is an air bubble in your cooling system or a thermostat.

Worst case, a head or head gasket. I'm betting on the air bubble because you aren't blowing smoke and there's no coolant in the oil.

-Fatz

 

Hi guys! Here's an update!

This morning i started up the truck dead cold with the cap open. No bubbles at all......nothing. I let the truck run for about 20 minutes and it wouldnt get hot enough to open the stat so i gave it a little gas and it opened up.
When it did open up, i could see bubbles in the radiator moving with the coolant flow. I also could hear the heater core gurgling. I kept doing this for about 15 minutes and the bubbles seemed to slow down.
Is this a symptom of air in my system or a blown gasket?? I hope it was just air, but i still dont think ive got it all out. I ran it with the cap off and heater on max. I just read somewhere else that i should park it on a hill or jack the front up to help get the bubbles out.
What do you guys think? Air in my system or a blown gasket/cracked head????

 

Pull the dipstick and look to see if it has a milky residue. This could indicate a blown head gasket or cracked head. This would allow coolant into the oil and cause the milkyness. It sound like the thermostat is sticking though, start by replacing it and see if that solves the problem.

 

Using a compression tester check the compression on each cylinder and write it down … then squirt a little oil in each cylinder and redo the test, if the compression goes up the head gasket is fine, if it doesn’t go up there is a problem.