Hello, gents. I think my truck may be on its way to the boneyard.

I recently started losing coolant. For about the last week I have to refill the empty reservoir after a 20ish minute drive on the turnpike. I could smell that burning coolant but couldn't find a leak. There's no obvious sign of leakage, no smoke in the exhaust, and the truck runs great.

I finally pressure tested the cooling system and found a loose hose clamp, which seemed like too small of a leak but I figured that had to be it. I pressure tested it again and it held pressure.

Then I drove it today and it still lost coolant. I checked the oil and it looked normal (no milkshake) but it was higher than it should be, so I think the coolant is draining into the oil.

I'm thinking I must have a cracked sleeve or block. I will add that I'm pretty sure I have a slipped sleeve that rattles for several seconds after startup, then quiets down. I'm starting to think maybe that sleeve finally cracked. One note is the truck has about 155k on it and does still have the original head gaskets, but I feel like a blown head gasket would ether make the truck run worse or be visibly leaking coolant, and would fail a pressure test.

Thoughts?

 

Pressure test it with the cap off of the oil filler.

 

@dr. mordo It may not help but mine ran fine with a crack in the head gasket causing over pressure. Over pressure will cause the your coolant to leave the tank via the overflow line.

My symptoms if it helps :

• no overheat
• truck would idle for 30 minutes without issue or significant coolant loss
• Some liquid from tail pipe - but it looked like normal condensation or a tiny bit heavier
• After 30 to 40 minutes at speeds from 30 to 50 MPH the tank would overflow and I would lose maybe an inch of coolant
• After the the tank dropped an inch or a little more coolant loss stopped

It was a head gasket and badly warped head in my case - my bet is poor head gasket replacement by a previous owner

 

Did any of your head bolts actually end up being loose, or less than the torque spec?

 

I had a similar issue on my 04. I didn’t have milkshake right away but after some driving cycles I had I lot of gunk under my oil cap. I had to drop the oil pan and pressure test. I could see a tiny amount of coolant coming down from under a sleeve. It’s not totally an accurate test since the crack can get larger when the engine is at operating temperature. It’s possible you don’t see any coolant if the crack is small enough while the engine is cold.

 

@Sixpack577 yes I had, according to my notes 2 loose bolts on each side 1 and 5 one side and 3 and 2 on the other. The one could have been cracked with a ratchet, the other 3 were significantly looser than the rest, based on the amount of force to start them moving

 

To the OP, Pull the plugs and inspect both them and inside the chamber with a usb boroscope. Look for burnt coolant on one of the plugs. Look into the bores while the system is under pressure and still warm. If you see any coolant bubbling in around the area where the head meets the block then you found a cracked block.

 

Your issue sounds similar to one that I experienced less than 2 years ago. Had a small hose leak - wasn't the culprit. Pressure tested and everything came back normal. Turned out to be a leak in my front cover/oil pump assembly. My mileage was also the same. Had it diagnosed it by dropping the oil pan and running the pressure test again to see where it was leaking. I ended up having the entire assembly replaced by a local indie shop.

 

Well, I got home and went to pressure test it again, and coolant is spraying out of the heater core hoses before I get to 15 psi. That's interesting because they held pressure just fine two days ago.

A previous owner managed to bend the heater core pipes up pretty bad, so I guess I'm not getting a consistent seal. I think I'm going to bypass them to see if the coolant level stabilizes.

That doesn't explain the elevated oil level, but my driveway is on a bit of an incline, so maybe I over-filled it a bit after the last change without knowing it.