Coolant in oil

[randomguy]

TBI L05 with 115k on it. Sent an oil sample into Blackstone and there is coolant in the oil. It’s not enough to be visible to the naked eye and I’m not noticeably losing coolant.

Is there a chance this is just intake gaskets or should I be planning head gaskets?

 

[PlayingWithTBI]

Mine was the head gaskets between 5-7 and 6-8 cylinders. It can be bypassing in the bolt holes on the heads and intake since most of them are drilled through into the water jacket.

 

[randomguy]

I’ve never done head gaskets before. Do the heads need machining generally?

 

[PlayingWithTBI]

Be careful how you unbolt them - in opposite order as torquing them. Put a straight edge on them and use a feeler gauge to see if they're still flat, same thing for the block.

I have to ask, why did you have a sample run unless there was something else going on?

 

[Supercharged111]

Be careful how you unbolt them - in opposite order as torquing them. Put a straight edge on them and use a feeler gauge to see if they're still flat, same thing for the block.

I have to ask, why did you have a sample run unless there was something else going on?

He could have been looking at oil change intervals. If the motor didn't overheat and waste a head gasket it's likely they can be cleaned and reinstalled.

 

[randomguy]

I wanted to get an idea of the health of the engine, it’s only averaged 5k a year for the last 20 years. Everything else in the oil is average except for the potassium and sodium levels.

The engine has not been overheated since I bought the truck last year, though I’ve only put 5000 miles on it. The previous owner did replace the water pump and quite frankly he did some stupid stuff with this truck.

 

[randomguy]

I forgot I replaced my spark plugs a while ago. These had at least 60k on them if not more.

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I wonder if the intake could be leaking into the lift valley? I know my intake is leaking a smidge on the front of the motor, it’s wet but not dripping.

 

[Schurkey]

Pressure test cooling system, look for leaks.

Yank all the spark plugs. Pressurize cylinders with air (100 psi is typical) look for bubbles in the radiator, and air escaping from the cylinder next to it.

If you don't see anything obvious...you'll probably have to yank the intake and look for faults on the gaskets, You find a failed intake gasket, I'd be tempted to put it back together with fresh gaskets after making sure the intake manifold is not warped. If you don't see any evidence of bad intake gaskets...pull the heads off and look for failed head gaskets and/or cracked castings--heads and block.

When my LO5 popped the head gasket between #3 and #5, I lost compression but no coolant.

 

[randomguy]

I’m going to dive into it here in a week. I’ll probably just do a compression test and end up pulling the intake. Already have the gaskets at least.