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Cooling system high pressure

6584 Views 4 Replies 3 Participants Last post by  charlie2512
2004 Dll 128,000 miles.
My sons disco started blowing coolant out of overflow on coolant tank and radiator hoses seemed very hard when engine hot. No skips, no oil in coolant or coolant in the oil. Bleeding air from top hose bleeder was only temp fix.
Pulled heads and found no issues with the head gaskets leaking coolant into cylinders, no squeaky clean piston tops.
Machine shop inspected heads, did valve job and resurfaced the heads.
Reassembled w/new headbolts and torqued per specs.
Problem still exists and not looking forward to pulling engine down again.
Any suggestions as to what the problem may be.
Hoses always seemed hard to me and it always seemed to be very warm but never over the middle of temp gage reading.
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I would do 3 things prior to tearing down the engine again. First do a coolant pressure test, get a scanner with real time and watch the operating temps both at idle, in town and highway driving and if need be do a chemical block test.
Did you replace the t/stat and coolant pressure cap?
Yes new hoses and T stat.
Will scan for temps and make sure there is no problems there.
Have ordered block test kit from Tool Topia so I can test for exhaust gases in coolant.
No did not replace pressure cap along with thermostat as it was doing it's job I think by relieving to much cooling sys pressure.
Have not received my chemical block test kit yet, hopefully tomorrow so I can check for exhaust gas in coolant.
Engine runs absolutely great, seems to blow off right after thermostat opens when engine at operating temp. and after driving several miles. Went out this AM to check things out and cooling system held significant pressure over night, hoses quite hard still. Does not act like there is a bad head gasket or cracked head as pressure does not bleed off over night.
I have checked old head gaskets over again and can find no evidence of a leak at any of the cooling passages and no tracks on the fire rings indicating compression leaking to cooling sys. Anyone have any thoughts on this, have never run into this particular problem.
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