Radiator help please!

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Mar 25, 2022 | 07:43 PM

#16

FuzzFace2

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From: Angier, NC

I dont know what the high or low should be but I look to see what they are across all of them but not to much of a different between the one next to it.
So if you had 135 140 135 140 145 150 I dont think I would worry but thats me
Dave ----

Mar 25, 2022 | 10:04 PM

#17

Franklin2

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From: Virginia

Quote:

Originally Posted by xtal_01

OK ... took out all the plugs ....

My thinking was no use putting the new radiator in if there is a head gasket leak .... I don't want to over pressure the new rad.

Funny, #6 was loose and I know I put them all in with a torque wrench (being over cautious since #6 was stuck when I got the engine).

I cleaned up all the seats with a round wire brush.

Got my new compression tester out.

Just did a quick test ... only turned over a few times on each cylinder.

Got about 135 to 150 on all six.

It had just started raining and I am working outside in VT till I get the new shop built.

I will do the test again tomorrow when it is dry and write down the #'s

I can't seem to find a # ... one book says with %10 of high to low ... another says within %25

So .... what should the compression be ?

Honestly I am surprised it is this high .... an 86 engine with at least 200K on it (had to replace the original one last year ... 250K and a rod bearing went).

Also, with this much compression, is it safe to assume I don't have a head gasket leak?

Thanks .... Mike

PS ... the #6 plug was not only loose but the seating area on the plug is full of carbon baked on so it was definitely loose for a while.

A compression test is not usually the correct test for a head gasket leak or a cracked hear or block. Those types of leaks are so small, that it does not lose that much pressure through them. The proper tool is a coolant system leakdown tester. Or just put it all back together and keep and eye on it. I am going to assume you are using the worthless stock gauges in the dash. A set of aftermarket guages mounted under the dash with real numbers on them are a good investment and can help you troubleshoot when things happen.

Mar 25, 2022 | 10:05 PM

#18

Franklin2

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From: Virginia

Quote:

Originally Posted by xtal_01

A compression test is not usually the correct test for a head gasket leak or a cracked head or block. Those types of leaks are so small, that it does not lose that much cylinder pressure through them. The proper tool is a coolant system leakdown tester. Or just put it all back together and keep and eye on it. I am going to assume you are using the worthless stock gauges in the dash? A set of aftermarket guages mounted under the dash with real numbers on them are a good investment and can help you troubleshoot when things happen.

Mar 26, 2022 | 08:20 AM

#19

kr98664

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Quote:

Originally Posted by xtal_01

My thinking was no use putting the new radiator in if there is a head gasket leak .... I don't want to over pressure the new rad.

For a radiator in good condition, even if you did have a major head gasket leak, the radiator cap should have relieved pressure long before the Mr. Creosote impression:

I suspect the radiator had a flaw that caused it to let go. Even if the cap was bad and didn't vent, I'd expect a hose to burst or let loose first. Good idea to replace the cap as a precaution, as you were thinking.

As Dave mentioned, a compression test won't always catch a minor head gasket leak. Those numbers look fine, by the way. For peace of mind, you can run a combustion leak check of the cooling system. This is the doohickey that looks like a turkey baster with some special test fluid inside. You run the engine for a few minutes and then draw a sample of the air at the top of the radiator. The test fluid changes color in the presence of combustion gas, indicating a bad head gasket leaking exhaust into the cooling system.

Mar 26, 2022 | 09:46 AM

#20

xtal_01

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Thanks ...

Thanks ... rain stopped so I am heading out to put the new rad it.

I am crossing my fingers it was just the rad.

I did get a new cap and a new thermostat

Thanks .... Mike