Oil in Coolant Resevoir

MicroBruin · **Posted:** Sat Jan 09, 2016 8:49 pm

Well, I'm finally getting the complete timing belt job done by a VM mechanic in Tampa in the coming days, and I guess the timing couldn't be better (no pun intended), because oil showed up in the coolant a few days ago. Truck runs like a top, other than air in fuel issues when sitting for more than a few days, and I don't think it's the head gasket. So, I'm thinking maybe the oil cooler?? Is there anything else that might cause this? My thermostat has been reading low lately, so that's getting replaced, along with the water pump. Any ideas or similar experiences? If all else fails, I guess the mechanic will let me know what I'm up against in a few days... My timing job probably just got a lot more expensive.... Oh well, I really like this truck...

Mountainman · **Posted:** Sun Jan 10, 2016 12:07 am

It could be the cooler, but I doubt it. It's usually HG. Are you sure that the engine isn't slowly consuming coolant? Shine a bright light into the reservoir with the cap off while it's idling. Look REALLY close, and you'll probably see tiny bubbles cruising to the surface. You might get a better price from Geordi, and he's a safer bet on these fickle machines. Engine probably needs rockers anyhow...

olypopper · **Posted:** Sun Jan 10, 2016 3:20 am

Oil pressure runs much higher than coolant pressure...........oil cooler is what I'll put my money on!

Mountainman · **Posted:** Sun Jan 10, 2016 1:17 pm

olypopper wrote:

Oil pressure runs much higher than coolant pressure...........oil cooler is what I'll put my money on!

I agree with your pressure dif notion, I hadn't though of that. I will mention though that the coolant passages on the head and block on the drivers side, sit really close to the oil passages.
I'm just going off of what we usually see though. Many HG failures, and maybe a couple of oil cooler failures. hmm, I'd say if it doesn't consume any coolant in a thousand miles, then maybe it's the cooler. Last one I opened that had oil in the coolant had a really nice stream of bubbles in the reservoir while idling.
What a mess the oil in the coolant makes. Radiator cleaner didn't phase the layer of slime in the reservoir...

MicroBruin · **Posted:** Thu Jan 21, 2016 10:41 pm

Well, turns out I don't need to worry too much. Kyle, the VM Motori trained tech at Florida Detroit Diesel Allison in Tampa tested it during the timing belt job (they are excellent, by the way), and it turns out it isn't oil. No oil in coolant, and no coolant in oil. Head gasket is fine, and he did an excellent job on the complete timing belt job, including a new thermostat, graf water pump, hayden fan clutch, improved serp tensioner, etc. He thinks maybe some grungy stuff let loose from a hose or something and collected on the upper walls of the coolant resevoir. There's nothing actually mixed into the coolant. The coolant tests fine, and the truck runs like a champ. So, I'll keep my fingers crossed, and start racking up some more highway miles. The thermostat gasket was leaking for a bit, and was most likely the last source of my coolant loss (the other was lower radiator hose), so I'm happy about that. My thermostat was definitely starting to stick open, and now works flawlessly. All is well in CRD land.....for now.

Mountainman · **Posted:** Fri Jan 22, 2016 12:55 am

MicroBruin wrote:

Well, turns out I don't need to worry too much. Kyle, the VM Motori trained tech at Florida Detroit Diesel Allison in Tampa tested it during the timing belt job (they are excellent, by the way), and it turns out it isn't oil. No oil in coolant, and no coolant in oil. Head gasket is fine, and he did an excellent job on the complete timing belt job, including a new thermostat, graf water pump, hayden fan clutch, improved serp tensioner, etc. He thinks maybe some grungy stuff let loose from a hose or something and collected on the upper walls of the coolant resevoir. There's nothing actually mixed into the coolant. The coolant tests fine, and the truck runs like a champ. So, I'll keep my fingers crossed, and start racking up some more highway miles. The thermostat gasket was leaking for a bit, and was most likely the last source of my coolant loss (the other was lower radiator hose), so I'm happy about that. My thermostat was definitely starting to stick open, and now works flawlessly. All is well in CRD land.....for now.

Glad to hear you dodged the bullet. I bet you got the goo from a bit of green antifreeze being added to the system at some point. Maybe it was flushed by a prior owner, but the goo is tough to get rid of. If it cools good then nothing to worry about though.

Oil in Coolant Resevoir

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