Oil in my Coolant

Oil in my Coolant

MtnMikes42

Jeeper
Posts
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Location
Union City, CA
Vehicle(s)
1980 CJ5 4.2L T4 Dana300 D30 4.88 ARB Rear AMC 20 4.88 sold axles
Hi All,

I have seen heads crack or warp, resulting in coolant in the engine oil. This is the expected error since usually the coolant pressure is higher than the oil pressure, as far as I know.

My 1980 CJ5 4.2L with Howell TBI now has engine oil in the coolant. After a 3 hour drive, I parked the Jeep getting ready to go 4 wheeling. I noticed black stuff coming out of the coolant overflow from the radiator, since I do not have a coolant collection bottle.

When I touched it, I realize it is more oil then coolant. :mad:

This jeep sat around for about 6 years without being driven before I bought it and started restoring it. It has a new radiator, water pump, thermostat etc.

I guess the starting point is to take off the head and send it to a machine shop for testing. :confused: Any other suggestions?
 
change the oil and flush /refill the coolant system, drive if for a bit and see what you have. I would do a little more investigation befor tearing the motor apart. and there is no water in the oil just oil in the water. I don't think oil in the water will do dammage to anything.:cool:

Hi All,

I have seen heads crack or warp, resulting in coolant in the engine oil. This is the expected error since usually the coolant pressure is higher than the oil pressure, as far as I know.

My 1980 CJ5 4.2L with Howell TBI now has engine oil in the coolant. After a 3 hour drive, I parked the Jeep getting ready to go 4 wheeling. I noticed black stuff coming out of the coolant overflow from the radiator, since I do not have a coolant collection bottle.

When I touched it, I realize it is more oil then coolant. :mad:

This jeep sat around for about 6 years without being driven before I bought it and started restoring it. It has a new radiator, water pump, thermostat etc.

I guess the starting point is to take off the head and send it to a machine shop for testing. :confused: Any other suggestions?
 
I second that.^^^

Mine had an oily film in the coolant that went away after replacing both oil and coolant.
 
When I touched it, I realize it is more oil then coolant. :mad:

This is not just a small film of oil draining out of the radiator overflow, the coolant is pitch black. The engine is about 2 quarts of oil low, which is apparently in the coolant system!
 
this isn't sounding good. You can swap out the coolant as IOPort suggested. That might tell you something. A little water in the oil will boil off but that much oil in the coolant could be a cracked block.
Check compression on each cylinder



.
 
i second the compression test, and if i'm a bettin man you have a blown head gasket
 
I hope Daves not right! but I am having a hard time wraping my arms around oil going into the coolant and no coolant going into the oil?
What do your plugs look like? I am currently rebuilding a motor that coolant got into the combustion chamber through the head gasket and first signs were fouled plugs.
 
I think coolant is going into the oil. It's just not as noticeable because it can boil off. Oil doesn't have a pressure cap. Water on a hot engine boils quickly. On the other hand oil in the coolant is there to stay.
I won't be making any bets with bdunnam because he may be right. A blown head gasket is more likely than a cracked block. And cheaper to fix too.
 
MtnMikes, If is your head and it needs resurfacing or? do concider upgrading to a 4.0 head or if you want to stay true and can't fix yours I have a just resurface and 3 angle ground 4.2 head I don't need anymore. Not trying to get ahead of you here but thought I'd throw that out there.
Hopefully it's just a gasket or something easy.
 
Hi All,

First confusing fact. The engine runs very smoothly even though it keeps pushing oil in to the coolant.

Second confusing fact. All spark plugs look normal.

Other facts:
I have not had a chance to do the cylinder pressure tests.

The engine is about 2 quarts LOW of oil.

What oil there is does not seem to be contaminated (no froth on top of the oil) and the oil looks normal. The coolant definitely has the missing oil. The last oil change and the coolant was replaced (with new radiator, water pump, thermostat etc) was less than 500 miles previously.

The engine did not seem to overheat and no steam was seen.

The engine always has had (since I bought it) a layer of grease/oil on the passenger side / back half of the engine. The starter motor is covered. I just assumed that this was natural for a 30 year old Jeep that has 61,000 or 161,000 or 261,000 etc miles on it.

When the engine is running, no spray of oil / grease can be seen. It just runs smoothly and happily. Go figure!
 
Although the Jeep sat for 6 years, I don't think the coolant completely ran out but I am not completely sure. When the previous owner started it before selling it to me, he said there was still coolant, but the heater core cracked and a lot of coolant ran out then. There was coolant when I received it. Radiator was only about 1/2 full...

Please keep in mind that it was parked in Fremont, CA. We don't get freezing days here even during the winter.
 
MtnMikes42, If you do have to take the head off or? Take some photos of your engine bay and details of the way hoses go etc. that will be the hardest part to put back together without any referance. The engine work is pretty easy to do but figuring out were all those hoses go is not.

In your profile the "AMC 4.88 solid axles" do you mean one peice axles or spooled diff? just curious.
 
Thanks for the reminder for the pictures of the hoses. Since I have the howell TBI installed, the amount of hoses is drastically reduced.

The solid axles reference is to the one piece axles with ARB lockers.
 
Thanks for the reminder for the pictures of the hoses. Since I have the howell TBI installed, the amount of hoses is drastically reduced.

The solid axles reference is to the one piece axles with ARB lockers.

Nice!
 

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