I have been chasing down this cooling issue for a while now, hopefully someone can shed light on my situation. I picked up the car at the beginning of this year with the M50 swapped in, I’ve been basically cleaning things up since.
This first started when I noticed the radiator was getting pressurized at startup. Used a block tester to check for HC in the coolant and came up with nothing, so I ended up getting a new (M42) radiator and t-stat for the car. Once that was in it ran/cooled great. After about 3 weeks of driving, it randomly started wanting to overheat.
Symptoms:
If I let the car sit and idle, it comes up to temp normally and then climbs slowly like you would imagine with no fan on and the car parked. I can basically let it sit idling for 15 minutes and it is fine. Now if I take the car down the road, as soon as it gets up to temp it gradually climbs in temp until I shut it off. If I start the car without the radiator cap on, it blows all of the coolant right out of the reservoir. Oddly enough, once the pressure is relieved, when using the block tester it appears to be creating a vacuum in the reservoir tank. Just recently in this whole testing process it has started to blow pressure out of the cap, even if cold and I only run it to pull out of the garage or something.
Here’s what I have tried:
-Swapped out thermostat – Current one is a alternate temp one and has the bleeder hole
-Bled the system multiple times (on a hill, also tried a burp bucket a few times)
-Compression test (180psi across the board, 2 cylinders lower but within 10psi)
-Flushed the coolant from the block drain
-Used a block tester to check for hydrocarbons, both through the reservoir and the bleeder hole (all tests negative)
-Oil doesn’t look milky at all. Under the filler cap is clean as well.
Pressure in the cooling system when the car is cold typically means head gasket, but I don’t see how that would be the case and yet I still get negative results when I test for hydrocarbons in the coolant.
If the HG is bad, I want to be able to prove it 100% before I tear the car apart to fix it. Any ideas what else this could be?
This first started when I noticed the radiator was getting pressurized at startup. Used a block tester to check for HC in the coolant and came up with nothing, so I ended up getting a new (M42) radiator and t-stat for the car. Once that was in it ran/cooled great. After about 3 weeks of driving, it randomly started wanting to overheat.
Symptoms:
If I let the car sit and idle, it comes up to temp normally and then climbs slowly like you would imagine with no fan on and the car parked. I can basically let it sit idling for 15 minutes and it is fine. Now if I take the car down the road, as soon as it gets up to temp it gradually climbs in temp until I shut it off. If I start the car without the radiator cap on, it blows all of the coolant right out of the reservoir. Oddly enough, once the pressure is relieved, when using the block tester it appears to be creating a vacuum in the reservoir tank. Just recently in this whole testing process it has started to blow pressure out of the cap, even if cold and I only run it to pull out of the garage or something.
Here’s what I have tried:
-Swapped out thermostat – Current one is a alternate temp one and has the bleeder hole
-Bled the system multiple times (on a hill, also tried a burp bucket a few times)
-Compression test (180psi across the board, 2 cylinders lower but within 10psi)
-Flushed the coolant from the block drain
-Used a block tester to check for hydrocarbons, both through the reservoir and the bleeder hole (all tests negative)
-Oil doesn’t look milky at all. Under the filler cap is clean as well.
Pressure in the cooling system when the car is cold typically means head gasket, but I don’t see how that would be the case and yet I still get negative results when I test for hydrocarbons in the coolant.
If the HG is bad, I want to be able to prove it 100% before I tear the car apart to fix it. Any ideas what else this could be?
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