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Discussion Starter · #1 ·
Started overheating intermittently on the way home...coolant tank full and bubbling...empty radiator..we are in Norcal so i was able to limp it back down the mountain where we parked over night. Next morning same thing. Had no choice but to limp it home an hour and a half North on the 101. We made it! It overheated a few times again but would go down as soon as the thermostat released..I just overhauled the engine 15,000 miles ago. new HG timing the works...So from what I found in my research is that it an internal HG leak into the chambers which is pushing the coolant into the overflow tank hence the bubbles. Am I right in my assumption? If so is there a way to test which HG has the leak?From what I read the compression test may not detect this? If I hadnt replaced the thermostat 6 months ago I would swear its sticking but I believe the boiling over coolant tank means HG. Any help appreciated

Also there is signs of coolant leakage at the top of the radiator and the smell of burning antifreeze. Drove it today and no issues yet...the radiator needed to be topped off though.
 

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Also there is signs of coolant leakage at the top of the radiator and the smell of burning antifreeze. Drove it today and no issues yet...the radiator needed to be topped off though.
Very possible you have a bad thermostat, or at least a sticking one. Even new parts can be bad, or perhaps during the overhaul some particles of trash remained in the system. Before tearing into it again, I would get a new thermo from the dealer, do a flush, thermo and refill. Or, you might get someone with a hydrocarbon detector to check the system while running (probably the best idea). Have you built several of these engines? Did you machine or replace the heads? Was the engine badly overheated before last overhaul and could block be damaged? Just my thoughts and I wish you good luck.
 

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Discussion Starter · #3 ·
Very possible you have a bad thermostat, or at least a sticking one. Even new parts can be bad, or perhaps during the overhaul some particles of trash remained in the system. Before tearing into it again, I would get a new thermo from the dealer, do a flush, thermo and refill. Or, you might get someone with a hydrocarbon detector to check the system while running (probably the best idea). Have you built several of these engines? Did you machine or replace the heads? Was the engine badly overheated before last overhaul and could block be damaged? Just my thoughts and I wish you good luck.
hey thanks man...yeah she was my first and I did have the heads machined and all that. I think I will atleast take it in for a sniff test before I assume anything
 

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Discussion Starter · #4 ·
Sniff test on the radiator confirmed exhaust gasses in the coolant. Bummed! Not sure if its the HG or the block??? Is a compression leak down test the best way to determine the problem?
 
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