351w gurus.. how bad is it..

[guidoverduci]

I’m hoping, but not holding my breath here, that the fix is at least something I can handle in my garage… but here’s the issue-

I noticed some brown gunk in my coolant overflow and decided to see if it was related to a possible blown head gasket. I tried a head gasket leak test with testing fluid tool inserted in the radiator. No color change. The coolant system was bubbling up as it got hot, I assume it’s just pressurizing normally. Then I did a compression check. One of the cylinders was 25PSI off the rest.. eek. Then I poured a tablespoon of oil in that cylinder per other google suggestions.. and it jumped up to about 140PSI and matched the other cylinders. How screwed am I?

 

[Timmy390]

Brown gunk could = rust. Iron heads and intake with wrong coolant to water ratio or low level you get rust and as the water flows it collects as a brown paste at the bottom of the radiator and recovery tank. Also you will see some around the radiator cap.

Do you have a recovery tank? Any bubbles in that tank once at N.O,T ? My experience with blown head gaskets, bubbles and or oil in the recovery tank/radiator or water in the oil i.e. "milkshake"

Tim

 

[cldonley]

If it's water in the oil it should be milky. If it's sludge like, probably just old gunk that washed out like Timmy said. If you don't have overheating issues and the gunk doesn't reappear, you're probably ok. 25psi isn't a huge difference, but if you add oil and it improves it indicates you have more wear on the rings/cylinder wall in that cylinder than the others. Was it warm when you did the compression check?

 

[guidoverduci]

Brown gunk could = rust. Iron heads and intake with wrong coolant to water ratio or low level you get rust and as the water flows it collects as a brown paste at the bottom of the radiator and recovery tank. Also you will see some around the radiator cap.

Do you have a recovery tank? Any bubbles in that tank once at N.O,T ? My experience with blown head gaskets, bubbles and or oil in the recovery tank/radiator or water in the oil i.e. "milkshake"

Tim

Yeah, it had been sitting for a couple months and I have done a bunch of work (nothing engine related). Brown paste is accurate around the bottom of the reservoir but nothing near the cap. I haven’t noticed any “milkshake“ anywhere.

If it's water in the oil it should be milky. If it's sludge like, probably just old gunk that washed out like Timmy said. If you don't have overheating issues and the gunk doesn't reappear, you're probably ok. 25psi isn't a huge difference, but if you add oil and it improves it indicates you have more wear on the rings/cylinder wall in that cylinder than the others. Was it warm when you did the compression check?

No overheating issues. 7 of the cylinders were 135-140psi and the one in question was around 115psi. It was warm when I did the test, but I didn’t hold the throttle open on the test which I‘ve read is helpful.

 

[Timmy390]

I would clean/flush the cooling system before I did anything else. Do some searching on using vinegar or maybe try the Evaporust radiator flush. Flush it out and go from there.

Tim

 

[1970 Palmer]

Change the oil, and replace the coolant. Drive it a few hundred miles and retest. The worse case is that it does not improve. It's well worth your time to give it a try.

 

[Broncobowsher]

Run it.

It's a used engine. You are expecting too much perfection. As long as it runs good, doesn't drink oil, it's fine. Perfect, no. But probably really good with years of life left in it.
Old coolant in a cast iron engine is typically pretty rusty looking. Just needs to be maintained a little better.