Inliners International Forums General Discussion AMC/JEEP Jeep 258 with coolant in the oil

Hello,

I decided to take my pickup on a journey to a family reunion
in Oregon.. I got as far as Anderson, CA. and that's when I
discovered mayonnaise in the oil filler cap..A few days later,
I trailered it back +500 miles home.

Anyone out there experience a cracked cylinder head on a
healthy running Jeep 258 that was NOT, overheating.. I'm guessing it was abused before I freshened it up and installed
it a year ago.. Any info on cracked 258 Jeep heads would be
appreciated.

If the "mayonaise" is only on, or in the oil filler, I would bet that it is simply condensate evaporating out of your oil. Does the vehicle do lots of short runs, or is started periodically to charge battery, and never fully warms up ?
A good hot run for a few hundred miles will sometimes show condensate in the form of a creamy goo on fillers, inside of rocker covers etc. Any high and a little cooler part of an engine. Lots of British cars I have seen do it.
Pressure test the cooling system as a precaution, but the condensation of water from previous condensation events would be my bet.
Particularly if the oil in the crankcase is clean and not milky.

regards,Rod.

x2 - what he said

T.F.T.F - I hope Mr. Melon is not too busy tearing his engine down before he reads our comments.

regards,Rod

I just returned from another trip. This time on my motorcycle.
Today, I'll do some investigating. I did fail to mention that
I also had about 1 quart of coolant disappear.. The engine was
freshened up about 3,500 miles ago and the cylinder head and
short block showed no sign of coolant leaks at that time. I checked the head and block surfaces for warping and then
installed a new head gasket. This engine never overheated
even once since I have owned it. The oil pressure and water
temps were always normal.

Also, I changed the oil and filter, 2 days before starting my trip. So, built up condensation wasn't considered.

Yesterday, I removed the valve cover and pressure checked the
cooling system @ 18 psi. I found a very small leak @ the bottom
radiator hose to the outlet. 1 drip every 5 minutes.

The lose of coolant (1 quart from overflow bottle) and the
mayonnaise in the filler cap and PVC valve lead me to suspect
a cracked head or block..

After leaving the tester on the system all night, I still have
10 psi in the system. At this point, I'm guessing that the
Alumiseal I put in a while ago to make the heater stop stinking, may be sealing a cracked head with the engine cold.

I'll drain and refill the cooling system with straight water. Get the engine up to operating temp and then do another pressure test. 500 miles in 80 degree weather with clean oil shouldn't be making mayonnaise in the valve cover and that quart of coolant
went somewhere...No noticeable external leaks..

OK, given all the additional information, I agree with you, there is a problem lurking somewhere.

regards,Rod.

Hello,

Yesterday I drained the radiator, refilled with well water and
pressure tested. I ran the engine until coolant was up to 190 degrees and the thermostat opened (cap off). I found one small leak at the bottom hose. I drained the oil. No contamination.
I re-examined the valve cover gasket..

You see before I started my trip, in addition to changing the
oil, I cleaned the engine...This was AFTER the oil change. I use
a degreaser and then blast it off with a garden hose with nozzle.

And...............That dang valve cover gasket had moved a
bit at the right front.. In fact it exposed a 1" area to anything
pointed at it......Like my garden hose.. The valve cover itself
had mayo only in the area around the breather hose and the PVC
hole.

I use Gaska Cinch to glue my valve cover gasket down and have
never seen a gasket shrink up so much...

At this point, I am just going to run the engine and keep an
eye out for evidence of water in the oil.. Thank's for your
ideas.. I'm hoping the oil leaks, loss of coolant and presence
of mayo just faked me out..... My old eyes force me err on the
side of caution.. Thanks again..

I had a 300 van that used a quart or two of coolant every summer. I never found any place it leaked. I assume it was going out the tail pipe. I drove it like that for years with no ill effects and no noticeable loss in performance. It was a mystery that I never chose to investigate (removing a head or engine from a van is no easy task) but I suspect a flaw in the head gasket or sloppy gasket installation. It never got worse.

Your plan to drive and monitor seems right to me.

It's been quite a while and I ended up changing to another 258.. The problem with the other one was a very small crack in the #5 cylinder...So the engine used a small amount of water, had a very small amount of mayo in the filler cap and zero in the drain oil every service.. I lived with it for a couple of years... The current 258 uses zero coolant.