How much does coolant degrade oil?
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
How much does coolant degrade oil?
While trying to diagnose an engine knock, I got my engine up to operating temperature for the first time since having it apart with a cut open valve cover on the passenger side. When I shut it off, I noticed coolant bubbling up past the head studs. I believe this started within seconds of me shutting the engine off, so it didn't look like coolant had flowed down the drains in the head. However, you could clearly see that there was green coolant in the oil at the head. This was not present on the other side, so I believe just the passenger side head was leaking. I sopped up the coolant-oil mix in the head and drained the rest of the oil, which looks fine. Am I safe putting the oil back in it, or could (at most) a few teaspoons of coolant contaminate all of my car's oil?
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
not sure what you're asking - you have a coolant leak at the RH cylinder head - you drained the engine oil, and you want to put the original, drained, oil back in the car - correct? if so, hard to say. since coolant is not a lubricant, and an unknown quantity of coolant, if any, contaminated the oil. I would say, why chance it. 5qts of oil at Wal-Mart is $15. personally, I wouldn't do anything until the leak is fixed. I think you have more than a $15 issue here. along with the oil, figure on a new filter. good luck.... 
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 178
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
not sure what you're asking - you have a coolant leak at the RH cylinder head - you drained the engine oil, and you want to put the original, drained, oil back in the car - correct? if so, hard to say. since coolant is not a lubricant, and an unknown quantity of coolant, if any, contaminated the oil. I would say, why chance it. 5qts of oil at Wal-Mart is $15. personally, I wouldn't do anything until the leak is fixed. I think you have more than a $15 issue here. along with the oil, figure on a new filter. good luck....
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
You should change the oil but what you really need to do is pull the studs and seal them with sealant so no coolant comes up past them. Pull one at a time and seal them.
Instructor
Joined: Jul 2016
Posts: 222
Likes: 11
From: Plymouth MI
While trying to diagnose an engine knock, I got my engine up to operating temperature for the first time since having it apart with a cut open valve cover on the passenger side. When I shut it off, I noticed coolant bubbling up past the head studs. I believe this started within seconds of me shutting the engine off, so it didn't look like coolant had flowed down the drains in the head. However, you could clearly see that there was green coolant in the oil at the head. This was not present on the other side, so I believe just the passenger side head was leaking. I sopped up the coolant-oil mix in the head and drained the rest of the oil, which looks fine. Am I safe putting the oil back in it, or could (at most) a few teaspoons of coolant contaminate all of my car's oil?
I usually recommend this on all major repairs made where the head and or intake is pulled off.
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
Yeah, I kinda figured I'd get a lot of "it's cheap, might as well change the oil" responses. It's just that I've already been through two or three batches of oil in 200 miles for various reasons and it's starting to add up. Plus even if I change the oil I'm interested for purposes of educating myself.
Just did that yesterday. 
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Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA