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I have an issue that is driving me absolutely nuts and I'm hoping one of you may have experienced something similar and found a solution.
'69 cutlass with 455. BeCool aluminum radiator, dual electric fans, 180 degree thermostat, and aluminum water pump. Everything is relatively fresh - around 1k miles on the drivetrain.
When I first warm the car up, the temp will slowly warm to ~180 degrees. About the time the thermostat opens, the temp gauge will spike to 230-ish within 3-4 seconds and back down to 180 (or less) almost as fast. It will do this a few times as the engine warms up. Once completely warmed up, the temp will settle at around 190 and stay there all day. I've assumed it's an issue with air in the system as I can't image water temps can actually fluctuate that quickly. I recently pulled the thermostat and put in a new 180 degree thermostat, but this time drilled two 1/8" holes to help bleed any air that may be in the system. Fired the car up and experienced the same issue - maybe even worse. Next I jacked the front of the car up to ensure the rad cap was the highest point in the cooling system. Started the car and let it run with the cap off. It burped a little air and I let it run until it started puking a little coolant out of the radiator and I shut it down. After that, I'm STILL having the issue.
At this point, I'm kind of stumped. Is it possible that the water pump isn't moving the water fast enough at idle? Again, I find it hard to believe that the coolant temps would spike that much in such a short time, but who knows. Maybe just a bad gauge? It's an autometer mechanical gauge. I have an Edelbrock Performer intake on the engine and used one of the ports near the thermostat. I did have to use an adapter, so maybe that could have put the sensor too high in the intake? Any other ideas from anyone? I hate to just throw parts at it.
Started the car and let it run with the cap off. It burped a little air and I let it run until it started puking a little coolant out of the radiator and I shut it down
My experience is when that coolant pukes is when the thermostat is opening, and right after that the level drops. It usually takes me several times repeating this to get the system full, or at least mostly full. I then top off the overflow reservoir and all the air gets purged after a warm up / cool down cycle.
What you described sure sounds like air in the system - I experienced a similar thing on one of my cars when there was a leak and the level dropped, but that was while driving and not right after starting the engine.
Your temp probe setup is the same as on my engine, so no issues with the probe not being in the coolant flow.
What does the temperature do when you start the car and drive it immediately?
Gary
Mostly the same thing...slowly rises to 180, then spikes to 220-230 within 3-4 seconds and then comes back down. The spike might be SLIGHTLY less when driving and comes back down just a bit quicker as well.
My experience is when that coolant pukes is when the thermostat is opening, and right after that the level drops. It usually takes me several times repeating this to get the system full, or at least mostly full. I then top off the overflow reservoir and all the air gets purged after a warm up / cool down cycle.
What you described sure sounds like air in the system - I experienced a similar thing on one of my cars when there was a leak and the level dropped, but that was while driving and not right after starting the engine.
Your temp probe setup is the same as on my engine, so no issues with the probe not being in the coolant flow.
Thanks - I'll maybe just have to be patient. I live in Wisconsin so have a short driving season, but it never fully resolved itself the entire summer.
When I first warm the car up, the temp will slowly warm to ~180 degrees. About the time the thermostat opens, the temp gauge will spike to 230-ish within 3-4 seconds and back down to 180 (or less) almost as fast. It will do this a few times as the engine warms up. Once completely warmed up, the temp will settle at around 190 and stay there all day
Emphasis mine.
If your car had merely an idiot light instead of a temperature gauge, none of this would cause the light to illuminate, you would go about driving the car without a problem and without a care in the world, and you would be right to do so.
There is nothing wrong with your car. There IS such a thing as too much information. Just drive your car and enjoy it.
Even though Christmas has passed, we're still in the Christmas season.
Which water pump did you use ? I cant remember the details from 5 years ago but when I rebuilt the 307 in my Wifes car I was comparing the new water pump to the old one and there is a small bypass (?) hole that was missing in the new pump. I sent it back and got a GMB pump and it had the hole. I honestly am not sure exactly what that hole does but if it is a bypass to allow some coolant flow and it is not there in your pump it might cause the issue ? Maybe somebody else knows exactly what that hole is for.
Just a thought.
My 455, (Delta 88 ragtop) with 140k will go to 220- 230 at idle after a few minutes maybe 240, running down the road it stays at 180-190, idiot light goes on at 245-250 I believe, i don't worry about it, I did install a TC and good industrial gage because the PO said it over heated, i think it's normal, drive it!
I have an issue that is driving me absolutely nuts and I'm hoping one of you may have experienced something similar and found a solution.
'69 cutlass with 455. BeCool aluminum radiator, dual electric fans, 180 degree thermostat, and aluminum water pump. Everything is relatively fresh - around 1k miles on the drivetrain.
When I first warm the car up, the temp will slowly warm to ~180 degrees. About the time the thermostat opens, the temp gauge will spike to 230-ish within 3-4 seconds and back down to 180 (or less) almost as fast. It will do this a few times as the engine warms up. Once completely warmed up, the temp will settle at around 190 and stay there all day. I've assumed it's an issue with air in the system as I can't image water temps can actually fluctuate that quickly. I recently pulled the thermostat and put in a new 180 degree thermostat, but this time drilled two 1/8" holes to help bleed any air that may be in the system. Fired the car up and experienced the same issue - maybe even worse. Next I jacked the front of the car up to ensure the rad cap was the highest point in the cooling system. Started the car and let it run with the cap off. It burped a little air and I let it run until it started puking a little coolant out of the radiator and I shut it down. After that, I'm STILL having the issue.
At this point, I'm kind of stumped. Is it possible that the water pump isn't moving the water fast enough at idle? Again, I find it hard to believe that the coolant temps would spike that much in such a short time, but who knows. Maybe just a bad gauge? It's an autometer mechanical gauge. I have an Edelbrock Performer intake on the engine and used one of the ports near the thermostat. I did have to use an adapter, so maybe that could have put the sensor too high in the intake? Any other ideas from anyone? I hate to just throw parts at it.
Ignore this. I've had several engines with mechanical temp gauges do this. Maybe this is indicative of a bypass problem, but your certainly not momentarily overheating.
Which water pump did you use ? I cant remember the details from 5 years ago but when I rebuilt the 307 in my Wifes car I was comparing the new water pump to the old one and there is a small bypass (?) hole that was missing in the new pump. I sent it back and got a GMB pump and it had the hole. I honestly am not sure exactly what that hole does but if it is a bypass to allow some coolant flow and it is not there in your pump it might cause the issue ? Maybe somebody else knows exactly what that hole is for.
Just a thought.
I'm nearly certain mine is the GMB pump as well, but not sure if it had the hole as shown.
Thanks for all of the responses. Sounds like there's likely nothing to worry about. I'll just have to learn to ignore the temp gauge until I've been driving a few miles!
