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oil in coolant, likely bad radiator oil cooler

13K views 10 replies 7 participants last post by  ElSupremo 
#1 ·
It started on my 94LT1 Caddy when the lower fitting for the oil cooler line started dripping fairly heavily. I noticed right away before any major oil loss and invesitgated... no rust or bad fitting, or hole in the line. Just seemed to be leaking around the threads.
I figured a cracked oil coller tank in the radiator and changed radiators since I had a spare radiator already.

When changing radiators, a bunch of brown coolant came out even though I had green coolant. Thickness is pretty normal and not really any caking up, but the overfill tank has brown residue. Oil level a litlle low, so pretty sure oil mixed into coolant at radiator.

Flushed and cleaned, and then new radiator.

Oil line still leaking for some reason with new (used) radiator.

Changed oil lines with brand new set, and still dripping at fitting at radiator tank.
When changing oil at this same time, no excess oil came out (removed 4 qts) and no signs of coolant. I know I added about 4.5 qts to engine, and I am four dots low on stick after running engine for about 3 minutes.

So.... unless my spare (used) radiator also is bad at the cooler tank, how am I low on oil?
Also, how is fitting on lower part of tank leaking again? Leaks behind threads, but that would have to be insane pressure to blow by threaded fittings.

I need to check coolant again to see if getting oil in it.
Also doing an engine compression check, although pretty certain head gasket cannot cause oil into coolant (would be vice versa).

Search function brought up two similar situations, but neither guy posted the findings or results.

Any ideas? Thanks
 
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#3 ·
Stupid question but when you did the oil change (w/ filter I'm assuming) did you start it for a few seconds, shut off and then add some to compensate for the amount that went into the empty filter, and then run for 3 minutes? If you added to full then didn't recheck after running that'd explain why it's low.

If the system hasn't been flushed in awhile it's easy to get a bunch of dark fluid out especially with those clay tablets. Crap settles to the bottom and once you take a hose off it's all there. Are you 100% sure it's oil? The oil will not mix with coolant and will float in spotty bunches in the catch pan. If some coolant was greenish and some orange/brownish but everything mixes you were simply due for a coolant change.
 
#4 ·
After running engine (week later) and checking oil I am four dots low on the dipstick. Pretty sure each dot is a 1/4 quart, which means I am one quart low. I wouldn't think the oil cooler line and filter would hold a whole quart, but who knows.

Car is a 94 and I've flushed before, no tablets in these cars. Only 96, I believe?
Pretty certain oil in coolant as it separated in catch basin, brown vs green layers.


Main question, could oil get in the coolant system any other way than the radiator? I put in a new radiator and same issue seemed to happen immediately.
Hmmmm
Excessive oil psi? How?
 
#5 ·
oil in coolant, likely bad radiator

Don't the oil lines use o-rings. Are you sure they are intact? It seems to me that if oil is getting in the coolant,then coolant would be in the oil as well. Those clay tablets do make a mess,and take forever to get rid of.
 
#7 ·
i am also leaking water from that exact same spot - where the oil cooler line meets the radiator. im pretty sure its doing that because when i swapped my transmission i let the motor sag for a moment (by accident) and this pulled on the oil cooler line and probably weakened the fitting on the radiator.

now i need to explore my options for replacing the radiator or jb welding it or something. damnit.

p.s. im not an expert but i doubt oil is getting in your coolant, the water leaking from the oil cooler fitting is just that, water leaking. and isnt brown coolant just rust? (use distilled water in your mix next time)
 
#8 ·
I'm leaking oil out of my cooler line (bottom fitting), not water or any type of oil/water mix. This is true before and after repalcing both the radiator and the cooler line assembly. Prior to the new radiator I was dripping out of both the top and bottom cooler line fittings while engine running.

I always use distilled water in my coolant system. No tap water.

Pretty certain it is oil as it most definitely separated from the coolant when I drained it.
 
#9 ·
Compression test came in as good, as I kinda expected.
All cylinders posted between 185 and 195 psi, and that was without heating/running the engine before the test.

My plan is to jump the oil cooler lines after pulling it from the radiator cooler. I should probably put a psi gauge on this oil line to see what the pressure is....just for kicks and giggles, esp since possibly two radiators in a row have leaking oil cooler tanks.

Pretty sure there is no other way in an LT1 to mix oil into coolant.
Anyone else have ideas?
 
#10 ·
It better to do a compression test when warm. You can have a problem with something not sealing correctly when its at operating temp compared to cold.

Why dont you invest in a non cooler filter adapter?
also, did you put a used radiator in? Have you tighten the line more?
 
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