hot head

**curly** · 05-28-2010, 06:57 PM

Help-Help-Help.When I start my 364cuci from cold the temp rises on the left head to 25deg more than the right head and continues to rise I guess until the thermostat opens.Once the thermostat has opened the motor will run at 180deg, even idling in the shed for 1/2 an hour.If I let it cool and restart the motor the same thing happens with the left head getting up to 200-210 deg on my new gauge and then rapidly cooling once the thermostat opens.I swapped the new gauge sender to the right head and it reads normal 180 deg.I used a lazer temp reading gun on both heads before the thermostat opened and there was a 20-30deg difference between left and right.Once the thermostat opened the head temps read with the lazer gun were within 5 deg of each other.Is this a sign of a blown head gasket or is it more likely to be a cracked head.It seems that once the thermostat opens the motor is happy to run at 160-180deg on the highway but I am guessing that it's getting a lot of water circulation to cool things even with a blown gasket.Now it's back to the shed to tear the heads off again and investigate.I'll get the heads crack tested while they off.

**BigRivy** · 05-29-2010, 12:35 AM

If you never checked this before you worked on it, are you sure that there is really a problem? Run a compression test on it and run a cooling system pressure test on it. If they check out okay and it runs okay and their doesn't seem to be any other problems then their might not be. Temperature rise before the thermostat opens is bound to happen in different parts of the engine. If everything is okay after the thermostat opens I'd say run it. At least until some other problem shows up. I sure as hell wouldn't just tear it apart unless I was damn sure that's what it was! That's way too much time and effort.

**DocModisett** · 06-01-2010, 05:21 PM

I agree with BR..... dont go looking for boogers when there aint none.... if you want to know the general condition of the engine , just run a compression test.... that will give you some idea....
If the engine runs ok ,, dont worry about it... if the engine is not running good then start finding out why.... but a compression test will tell you if the engine can be made to run ok....
You can drill a 1/8th in. hole in the flange of the thermostat that will stop some of the difference by letting some of the warm water into the rad as it warms up... it slows warm up a little but lessens the shock on the rad when the thermostat opens up.... but from what you described , the engine seems pretty much normal....