Headgasket?

[darxranga]

This is the quick rundown I have an 81 non turbo. It overheats bad pretty quick. The cooling system(radiator, fan, water pump, thermostat) has all been replaced recently and is in good working condition. My thoughts are broken headgasket. There is no mixing of oil and coolant so I would assume it is broken between cylinders. I compression tested it and these are the results:

1. 174

2. 156

3. 155

4. 160

5. 173

6. 179

I have not diagnosed many engines, is the psi difference great enough on cylinders 2 and 3 to warrant my belief that it is a headgasket? Any other thoughts/ideas?

Side note: The test was done cold. The car has been sitting for a while and I have been tinkering. It was also done dry, no oil added.

What do you think? Am I missing anything?

[d240zx2]

What procedure did you use when performing the test?

[MikeW]

I'd think that if the gasket was damaged you'd see an even lower pressure and that it would continue to leak down since the adjacent cylinder would have an open exhaust or intake valve. Let's back up to the overheating problem ... how do you know it's overheating? Is steam coming out or is the temperature gauge pegged to the right?

[darxranga]

What procedure did you use when performing the test?

I left all the plugs in except the one being tested, disconnected the power from the injectors and the plugs then cranked at wot for 10s. Repeated for each cylinder

[darxranga]

I'd think that if the gasket was damaged you'd see an even lower pressure and that it would continue to leak down since the adjacent cylinder would have an open exhaust or intake valve. Let's back up to the overheating problem ... how do you know it's overheating? Is steam coming out or is the temperature gauge pegged to the right?

Temp gauge was pegged and coolant was gurgling. Cant remember ever seeing steam coming out. When the temp gauge went past normal and kept rising, I killed it pretty quick.

[MikeW]

The reason I asked is that it's possible that it's a gauge issue or a sending unit problem. I'd be inclined to take off the radiator cap and measure the temperature directly. The gurgling sound could be air in the cooling system.

[ajmcforester]

Temp gauge was pegged and coolant was gurgling. Cant remember ever seeing steam coming out. When the temp gauge went past normal and kept rising, I killed it pretty quick.

Note gurgling is never good. Air in the system can keep the pump from pumping properly or at all. Make the thermostat not open when needed, and reduce or stop flow threw all or some of the engine passages.

How well is the fan working, and when did you replace the fan-clutch?

Are you lousing fluid? If yes do a pressure test and find the leak, if a bad head-gasket is the problem you will have fluid rushing out in a pressure test. You can't really fix an overheating issue till the leaks are fixed.

If your answer is no it's probably not the head-gasket. It would more than likely be a flow issue. Problems can be a bad thermostat, radiator cap, pump, trapped air, blockage or restrictions. What I do is get a new thermostat, and maybe a new radiator cap. Then drain the system and flush the whole system. Detach the hose and blast the radiator out, make sure water flows easily threw it do this to the engine also (if the 81's have a coolant drain plug like the older ones pull it, and flush it out good). Take the old thermostat out fill with water and run it for a wile and drain it, then put the new one in (make sure water is flowing threw the heater core I don't know if 81's had a shut off to the heater core).

If that don't work you have a bad water pump, lot of blockage in the engine or the radiator. You can check the pump with a pressure gauge that Auto Zone has as part of the loan a tool program. If that test good, then I look at a new or reconditioning the radiator. If that don't work, new heater core. If that didn't help, I'd be getting ready to pull the freeze plugs and look for blockages, and considering pulling the engine out for recondition as my last option. Be side if you pull the engine out to recondition it you would need to replace those parts anyways.

Another thing to check make sure you have good oil flow

[darxranga]

Sorry I was out of town for a few days. I was loosing fluid so I don't think it was just the gauge but I have been wrong before. The thermostat, radiator, radiator cap, fan clutch, water pump, and radiator hoses are all less than 6 months old.

[ajmcforester]

Do a pressure test on the coolant system you should find the leak. They have the tool at Auto Zone for that, in their Loan-A-Tool program. If you can't find the leak with just the pressure test get the special die and do it again. Before you start the test see what your oil level is and see if it goes up after the test. If you can't find it the first time and you used the die don't forget to check the tail pipe for the die. Let us know what you find from this.

Trust me one will know if the head-gasket is what is leaking coolant. You will find it in the oil, exhaust, and/or poring out around the head. Don't forget the heater core.

[olzed]

Hi! I had a similar problem with my 240,with 2.4 motor. It occured after I had changed the water pump. On first start up the engine seemed to get hot too quickly so I shut it off,to let it cool ,then started it with the engine side heater hose loose and the radiator cap off. With the hose loose and me refilling with water ,and then tightening the hose with the engine still running ,I managed to purge the system of air,and that fixed the issue.Just watch you don't drown the alternator,as they dont like water.

[darxranga]

Last night I put it back together to start it and revisit the symptoms. It didn't want to start and the cooling system pressurized just from cranking. Pulled a spark plug and cranked it and there was coolant mixed with the fuel...

[ajmcforester]

Do you mean you have coolant in the intake or do you actually mean in the fuel system?