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High pressure in cooling system

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laser90

15+ Year Contributor
245
9
Sep 9, 2003
West Palm Beach, Florida
Ok To start off while driving I noticed the temp starting to creep up, so I pulled over checked and added coolant. When I got home I was checking the hoses to see if the thermostat was sticking. When checking the hoses I noticed all my hoses were swollen. I figured it was the cap, it was pretty old so I changed the cap and burped the system. No change so I removed the thermostat. No diffrence all the hoses still swollen. I've pressure tested the cooling system and cant find any holes in the system. Here's a list of what ive done.

- Fans run off ignition
- No thermostat ( now )
- New cap
- coolant topped off and burped

I was starting to wonder if the head gasket is blown or the head warped. My motor was just rebuilt 8,000 miles ago. A machine shop rebuilt it with ARP head studs and I am unsure what head gasket they used. I ran a compression test and heres my results #1. 150 #2. 150 #3 120 #4 150. the reason im posting is the car isnt showing the classic head gasket signs oil is fine and no white smoke. I'm wondering if my compression numbers are telling me it's a definate on the head gasket? Thanks for any help.
 
you can get pressure in the cooling system from a bad spot in the head gasket. It might not be blown completely but even to let a little compression by. if it is coming through the right spot it will not go into the oil or through the exhaust . i have heard that most people will experience coolant coming out of the overflow bottle if the head gasket is letting compression into the system.
 
Sounds like the compression you are losing on cyl 3 is getting into the cooling system.
 
I re-did the compression test and added a little oil in cylinder #3 anf the compression rose to 150psi. I trying to get my hands on a cylinder leak tester. I guess i'll pull the radiator and heater core and clean them out (maybe get lucky and solve my problem :pray:) LOL.
 
If you have a compression tester you can build your own leak down tester. Check this out. It might cost you $20 at the most. You need compressed air and you can eliminate the regulator if you have one on your air compressor. Way cheaper than buying one. When you hook the leakdown tester up take your rad cap off and check for bubbles.
 
I am having the exact same problem but my motor doesn't even have 100 miles on it yet and I'm running a .074 cometic head gasket. The car runs great besides the extreme pressure in the cooling system. I've had to get a universal overflow from autozone and gorilla glue and screw the lid to the reservoir just to keep the lid on it and it still blew a pin whole through the lid. I haven't done a compression test yet though. But like I said, the car is impressively fast and has no problems until I start running out of coolant.
 
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