I have an 88 NA that seems to have high pressure in the cooling system. I have flushed the cooling system, installed a new Mazda thermostat, pressure cap, and fill cap. I will start the engine and the add coolant light comes on and the cooling hoses get stiff as well. I turn the engine off and will check the coolant level at the fill cap and there is coolant in the system and is visible. I have checked for an exhaust gas leak into the cooling system with a block tester and the liquid stays a bluish color. I have removed all accessory belts and installed the Atkins serpentine belt and pullies.

I'm to the point of thinking there is a possibility of an exhaust/coolant leak from the engine that did not show from the block teseter kit or the water pump is creating air pockets increasing the pressure of the cooling system. There is white smoke on start up. I have the Atkins thermal pellet installed and I premix the gas before installing it into the gas tank. I believe the white smoke is from the thermal pellet and possibly the premix due to the strong gas smell. I have a shop service manual and have looked through it but didn't see anything into what could be causing the problem, or didn't look in the correct area.

Any help or direction would be helpful. I'm looking to sell the car, but would like to make sure the engine is good and there are no major problems with it before selling.

 

It’s likely a coolant seal failure, probably on the exhaust phase of one of the rotors. It’s pressurizing your cooling system and the white “smoke” is coolant steam. Usually there’s a sweet smell associated with it.
There are test strips available at most chain parts stores to check for hydrocarbons in the coolant.

 

Thank you, I will look into the test strips. Was really unable to smell the smoke myself, at some point I've lost my sense of smell and could not tell which one it was.

 

I had a leak right around the spark phase, which produced no visible smoke and also did not trigger the exhaust-in-coolant test. It would slowly fill the overflow tank along with the low coolant buzzer and pressurized lines. After letting it sit for a while you can try cranking it a bit as if you were doing a compression test, then removing the spark plugs, I found that they were visibly wet. You could also do an actual compression test when its cold, you'll get an abnormally high compression in the leaky chamber due to water sealing things up. I got 140+ PSI on the leaky and ~120 on the normal one (measured via a regular meter, hence the single number, but that does not matter for this). Do not start the engine for these as that'd clear the water. You can also try pressure testing the system, although mine behaved pretty randomly and would hold pressure just fine all but one time I tried.

 

Coolant was low, not really sure why I didn't check that first. Over flow hose was restricted.
Added coolant and removed restriction. Retested and no light or firm hoses.

 

Good to hear it was something simple. Was there quite a bit of air in the system?