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Overheating small block
I know this is a constant topic and have tried alot of the suggestions given here, changed thermostat, no thermostat, bled system, etc.
My problem is the car is fine for about 20 minutes or so and it runs at normal temperature. It has an electric fan which kicks in immediately on start up. After about 20 minutes of normal driving the temperature then starts to climb fast and throws fluid out the overflow. I turn off the car and if I try to loosen the cap slightly there is alot of "gurgling" in the tank. It is not consistent sometimes it will not overheat but after driving for awhile and I shut off the car the systems then does alot of "gurgling". The last time it overheated the top rad hose had collasped. It may well be an "air pocket" problem.... I am now considering an intake manifold mounted unit that Moroso markets with the filler/pressure cap right on the intake manifold. It has predominantly British items on it such as a "Kenlowe" thermostat unit to kick in the fan. Any suggestions? |
It sounds like you may have a blown headgasket. Try this! Remove radiator cap, start engine and let it run to heat up.Watch for air bubbles as the coolent moves thru the system. If air bubbles are present, you have a blown head gasket or worst a cracked block or cracked head. The system is drawing air from some where.
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I just had another thought. Check the timing. Too much timing can cause the problem you discribe.
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I agree with S1 - it might be a blown head gasket - if you have any contact with a manufacture/dealer shop they can test for exhaust gas in the water - others might have the test equipment but i don't have any experience except at the local Honda dealer
I assume that the car was running fine and now has slowly evolved to overheating - good luck jim |
Thank you for that timing thought, the car has been "jerky" lately when driven at a constant cruise speed so I suspect the timing may be off. I appreciate the assistance.
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I had the same problem. Not a blown head gasket, but a loose head. retorqued the heads, have not had the same problem since.
FWIW... Good Luck! It may be serious, but there is also a chance it is simple like mine. |
Actually the car was running fine and quickly evolved to the overheating problem I am now having.
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I had a cracked block on a 302 that would act that way. It wasn't easy to do but a slipping water pump during some open track time (Not looking at gages) managed to over heat it to the point it cracked.
Anyway, it acted just as you describe. Much more likely it's the head gasket but in my case I realy screwed it up big time. |
Thank you all for your advice....I bled the system (I hope completely), replaced the head gasket (looked fine)- torquing it properly, set the timing and removed the thermostat and the result is the same problem still persists. I think it is time to go to a specialist as it is difficult to check the cracked block question. Any other suggestions appreciated before it goes off to a shop.
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removed the thermostat? that isn't a good idea, it needs to regulate the coolant flow.
Got a leak down tester? One at a time, take each cylinder to BDC, pressurize, and see if air bubbles come out the radiator cap. How is your radiator? Possibly have some internal blockage? Does it only overheat in traffic, or will it stil get hot with high speed airflow through the radiator? |
Just to respond to the last question......it is a time thing as opposed to traffic.....in traffic it takes 15 to 20 minutes ...at moderate cruising it takes 15 to 20 minutes.
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you haven't mentioned your water pump...maybe it's just not pumping enough flow to keep up with your cooling needs and the problem presents itself within 15-20 minutes as the engine heats up.....must be pumping some, but not enough.
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OK the rad is coming out tonight for a check and I have an extra water pump i know is fine so it will get installed along with the rad.
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Things just sound too violent to be a matter of simply decreased cooling capacity.
When I had this problem I kept throwing "cooling enhancers" at it. Smaller waterpump pulley, less "coolant" and more distilled WATER, water wetter, lower pressure cap, higher pressure cap, lower t-stat, higher t-stat, etc... All of these band-aids did very little to fix the hole in my engine. Luckily, torquing head bolts fixed it. If block is cracked or something, all of these little issues are moot. Could be a stopped up radiator, but your inital post just seems to be pointing at a more serious issue. I hope I am wrong! Good luck... |
Does anyone know how one can tell if the water pump is not operating properly. I have it off, it turns freely, looks clean inside, impeller looks to be fine etc......working on taking out the rad now.
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Well, thank you all again for your help with excellent advice as I always get in this forum. The problem ended up being flow capacity of the radiator. After installing a new high flow water pump, testing it and the car overheated. Then I installed a manifold mounted cap and thermostat... overheated again after the system was bled. I went back to the rad again since it was all it could be except a cracked block. It was hard to tell if there is blockage since it was moving liquid but just not at a rate high enough. I would have loved an aluminum one but opted to go with a rebuilt one with about 30% higher flow. I am very relieved to find out it was not a cracked block.
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glad you got it worked out, and just in time to drive down to DVSF in Ohio!
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