Engine coolant temperature swing
Thread Starter
Heel & Toe
Joined: Jan 2017
Posts: 16
Likes: 0
From: Ballston Spa New York
Engine coolant temperature swing
Hi All,
I was driving my sons 1984 C4 today and noticed the coolant temperature got very high. It was around 250 when I noticed it. The temperature started going down pretty rapidly before I could pull over. Coolant temp got down to 170 so I kept driving. About 10 minutes later the temp started rising again and got back to the 250 range. Seems to continue doing this.
Any suggestions on what could be the problem?
I was driving my sons 1984 C4 today and noticed the coolant temperature got very high. It was around 250 when I noticed it. The temperature started going down pretty rapidly before I could pull over. Coolant temp got down to 170 so I kept driving. About 10 minutes later the temp started rising again and got back to the 250 range. Seems to continue doing this.
Any suggestions on what could be the problem?
Pro
Joined: Aug 2016
Posts: 551
Likes: 42
From: "Exit 8" New Jersey
Hi All,
I was driving my sons 1984 C4 today and noticed the coolant temperature got very high. It was around 250 when I noticed it. The temperature started going down pretty rapidly before I could pull over. Coolant temp got down to 170 so I kept driving. About 10 minutes later the temp started rising again and got back to the 250 range. Seems to continue doing this.
Any suggestions on what could be the problem?
I was driving my sons 1984 C4 today and noticed the coolant temperature got very high. It was around 250 when I noticed it. The temperature started going down pretty rapidly before I could pull over. Coolant temp got down to 170 so I kept driving. About 10 minutes later the temp started rising again and got back to the 250 range. Seems to continue doing this.
Any suggestions on what could be the problem?
Thread Starter
Heel & Toe
Joined: Jan 2017
Posts: 16
Likes: 0
From: Ballston Spa New York
Could be thermostat sticking closed then opening when it gets really hot. I had a similar problem when driving my Caprice convertible home from Iowa (where I purchased it) back in 2001. Problem got worse so I pulled of the highway and bought a tool kit and thermostat and changed it in a parking lot in like Illinois somewhere. Car never overheated again...still has the same thermostat.
Thread Starter
Heel & Toe
Joined: Jan 2017
Posts: 16
Likes: 0
From: Ballston Spa New York
Solution to temperature swing and I'm an idiot
Thanks to seabright and Edv I found the problem. Coolant was nearly completely empty. I feel like an idiot now.
Now on to figure out where the coolant is leaking....
thanks for the feedback guys.
Now on to figure out where the coolant is leaking....
thanks for the feedback guys.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
It could be going to ground. As coolant heats it expands, and should flow to the over-flow bottle. If the gasket in the radiator cap is deformed, coolant will flow out of the neck to ground.
The cap may be original, so even if it looks undamaged, replace it with the proper pressure rating.
Check all hose ends for cracks and tightness. Look for wet areas on the fins of the radiator, and pressure test, if suspect.
If the rad is leaking, coolant would be more noticeable on the ground when you first park the vette when internal rad pressure is at its highest.
Depending where a leak may be located, evaporation of coolant may mask the source.
Check for dampness in passenger side floor for a leaking heater.
Check for any signs for a leaking water pump, and tightness for all coolant hose ends in engine bay.
The cap may be original, so even if it looks undamaged, replace it with the proper pressure rating.
Check all hose ends for cracks and tightness. Look for wet areas on the fins of the radiator, and pressure test, if suspect.
If the rad is leaking, coolant would be more noticeable on the ground when you first park the vette when internal rad pressure is at its highest.
Depending where a leak may be located, evaporation of coolant may mask the source.
Check for dampness in passenger side floor for a leaking heater.
Check for any signs for a leaking water pump, and tightness for all coolant hose ends in engine bay.
Last edited by don hall; Jan 30, 2017 at 04:40 PM.
Thread Starter
Heel & Toe
Joined: Jan 2017
Posts: 16
Likes: 0
From: Ballston Spa New York
It could be going to ground. As coolant heats it expands, and should flow to the over-flow bottle. If the gasket in the radiator cap is deformed, coolant will flow out of the neck to ground.
The cap may be original, so even if it looks undamaged, replace it with the proper pressure rating.
Check all hose ends for cracks and tightness. Look for wet areas on the fins of the radiator, and pressure test, if suspect.
If the rad is leaking, coolant would be more noticeable on the ground when you first park the vette when internal rad pressure is at its highest.
Depending where a leak may be located, evaporation of coolant may mask the source.
Check for dampness in passenger side floor for a leaking heater.
Check for any signs for a leaking water pump, and tightness for all coolant hose ends in engine bay.
The cap may be original, so even if it looks undamaged, replace it with the proper pressure rating.
Check all hose ends for cracks and tightness. Look for wet areas on the fins of the radiator, and pressure test, if suspect.
If the rad is leaking, coolant would be more noticeable on the ground when you first park the vette when internal rad pressure is at its highest.
Depending where a leak may be located, evaporation of coolant may mask the source.
Check for dampness in passenger side floor for a leaking heater.
Check for any signs for a leaking water pump, and tightness for all coolant hose ends in engine bay.
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
If it came back down to 170 I bet it had to have had coolant. You night want to do a test for combustion gas in your radiator or sludge in the oil. Might have a leak in the head gasket. Mine would intermittently overheat replaced thermostat radiator kept thinking ok its fixed because it wouldn't do it for a couple days. But it kept returning. Blue Devil working so far 2 years now.
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
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