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DOHC guys: cooling system problems in my 1994 DOHC - FIXED, thanks all!


ManicMechanic

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I'm new to the DOHC...I replaced a freeze plug last week in the car and after refilling the cooling system, I opened the bleeders and let it run until they peed coolant. Ran good, no overheating and stayed at 190. Didn't even run hot when the freeze plug let go and it pissed coolant all over the ground.

 

Jump to this morning, I replaced the water pump because, One: it was still the original pump; Two: there was a noise like the PS pump was real low and it wasn't the PS pump; Three: a water pump was $22.

 

After replacing the pump and bleeding the system, the gauge now goes from cold to hot and back...I bled the system again and same symptoms. At idle it stayed at 200 but took it out for a drive and it shot up to 230-240 and then hovered around 215.

 

I took it to Taco Belch earlier and the gauge shot up to the first red mark (enough to turn on the Check Gages light) and stayed there all the way to TB...I went inside and got my food, came back out and started it up and the gauge was at 200...Now, I know damned well that it did not cool off that much in 5 minutes, if anything, the temp should have gone up. The gauge went up to the middle and stayed there occasionally going farther up and back down to the middle until I got home.

 

There's nothing coming into the overflow, the coolant level is where it's supposed to be and the heater will make you feel like you're in an oven.

 

Is my gauge now wonky for some reason or could it really be running hot? The fans seem to be working fine.

 

I'm going to replace the t-stat tomorrow because it's a $10 or less part and see what happens...I wanted some ideas here as to what might be causing this...

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I would say if it is realy that hot when you shut it off the coolant would be raipdly going in to recovery tank if its not i would wonder about the gauge not being right

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Sounds like an issue with air in the coolant system to me. I would confirm that there aren't anymore leaks and then go from there. It wouldn't hurt to verify the temperature readings you're seeing on the gauge and see how accurate or inaccurate they really are.

 

What water pump did you go with by the way? There are some cheapo pumps out that aren't designed like the originals. They've been discussed here before.

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The bleeders pee a steady stream of coolant for minutes...So I'm not convinced there's any air in the system.

 

This just happened today...So I am going to see if I might have accidentally unplugged something.

 

Went with a Duralast from AZ....Never had a problem with them before.

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Do the electric cooling fans work properly?

 

Radiator cap holds pressure?

 

I have had thermostats that began to stick, but only after the engine overheated for some other reason. (it wasn't the thermostat that caused the overheating to begin with)

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I have had thermostats that began to stick, but only after the engine overheated for some other reason. (it wasn't the thermostat that caused the overheating to begin with)

 

Yep, they bend.

 

It was the t-stat...Installed a new one and it goes to 190 and stays there. The old one only opened 1/4 of the way.

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