F134 - Coolant in oil

[Cabin Fever]

Lubed the M38A1 yesterday and then took her off the blocks. Put in the batteries and checked the coolant level. Coolant was down 2 quarts! Hummm? I don't remember the last time I checked it in the fall, but it was never this low.

At any rate, the Willys started right up, so I drove it for a couple miles to let it warm up so I could change the oil and filter. When I poured the used oil out of the drain pan and into the 5 gal oil recycle bucket I saw the green Prestone.

So, before I get started with a repair, I'd like to know what is the most likely cause for coolant leaking into the F134 engine? Head gasket? Cracked block? Something else?

The engine runs fine and the exhaust has no white smoke (steam) or water dripping from the tail pipe. The temp gauge does not indicate any overheating.

Thanks

[Joe Gopan]

First thought is head gasket. Also, remember the head bolt unde rthe carburetor, should you get that far.

[Dokimos]

Check the engine oil for white sludge indicating coolant going inside the oil

Also check if there is some brown mud in the coolant,

I had the same problem like you and it turned out the the main oil galley had cracked...

[artificer]

Pull the head? Not yet!
DIAGNOSE:
You need to know what you are most likely fixing, before pulling anything apart.
First a compression or leak down test to eliminate the head gasket area
if this shows nothing in particular....
then pressure test the cooling system to establish exactly where the coolant leak into the engine oil is coming from.

[Joe Gopan]

The need to visually check the valve guide and valve seat area for cracks should not be overlooked as this is a weak spot in this type engine.

[Cabin Fever]

Pull the head? Not yet!
DIAGNOSE:
You need to know what you are most likely fixing, before pulling anything apart.
First a compression or leak down test to eliminate the head gasket area
if this shows nothing in particular....
then pressure test the cooling system to establish exactly where the coolant leak into the engine oil is coming from.

How does pressure testing the cooling system show exactly were the leak is if the leak is internal?

I was told that if I see bubbles in my coolant as I rev the warm engine and/or if you have white exhaust, chances are its a leaking head gasket. I have neither problem.

Sorry, I am a newbie at this. I'm pretty good at swapping parts and routine maintenance, but diagnosing internal engine leaks is a new adventure for me.

Thanks!

[artificer]

Pull the head? Not yet!
DIAGNOSE: You need to know what you are most likely fixing, before pulling anything apart.
First a compression or leak down test to eliminate the head gasket area....if this shows nothing in particular....
then pressure test the cooling system to establish exactly where the coolant leak into the engine oil is coming from.

How does pressure testing the cooling system show exactly were the leak is if the leak is internal? I was told that if I see bubbles in my coolant as I rev the warm engine and/or if you have white exhaust, chances are its a leaking head gasket. I have neither problem.

That is good & the compression test being fine means there is no need to be pulling any cylinder head yet or maybe @ all!

Diagnostics is about eliminating things that are good, eventually isolating what is bad.

If the compression/leak down test was good plus what you were told about bubbles in the radiator neck, also indicated by always loosing coolant out the overflow after a very short time of engine running because the lost compression is pumping up the radiator & the radiator pressure cap lets that excess pressure & coolant out, is a correct diagnostic type observation, then you go to the next step.

This is not pulling the cylinder head to have a peek.
All this does is cost you time & money + it screws you up from being able to diagnose & pin point the internal leak if there is one.

Pressurize the coolant system to about 10 psi. This can be done with a purpose made pressure tester you can get on free loan or rent from AutoZone or similar. One can make a homemade one from an old radiator cap & tubless valve stem with schrader valve + rubber seal as long as pressure can be regulated to <10psi.

This pressure when applied should not leak down over about 10-20 minutes.
If it does then remove the oil pan & with your flashlight establish where the coolant leak is coming from.
May be where the oil pump & distributor drive goes & this can be repaired simply without pulling the head & spending unnecessarily [or the leak may be somewhere else...so tell us when you find out where & we will walk you through what to do & how]

[wo2jeeper]

How should this be repaired simple then (the shaft)

[Cabin Fever]

Thanks again, John (articifer) for your help. I am going to attempt to find a shop that will rent me the equipment I need for the cooling system pressure test, cylinder pressure test, and cylinder leak down test.

For the leak down test, is there an easy way to tell when I have my cylinders at TDC for compression and not exhaust? (Or, does it even matter?)

[artificer]

You can probably borrow most from guys on here if they know where you are. Some may volunteer to help. Many auto supply houses will loan them as well.
Your leak down:
Modify a broken off spark plug braze in air connector so as to adapt to air lead & feed in limited air pressure.
As for piston positioning:
Read through this & adapt to your F head 4 cylinder engine....follow the 180* apart chalk mark suggestions when you have established 1TDC compression.
http://www.jeepdraw.com/images/ADJUSTIN ... IBBINS.pdf

[artificer]

Let's get back to the beginning "COOLANT in OIL", restart & put things in a logical correct perspective....IF....
1. The engine is not running rough like missing on 1 or more cylinders
2. All the spark plug's electrodes are the same colour. One or more clean indicates coolant in that/those cylinder/s
3. There are no bigger than normal bubbles in the radiator neck when the engine is running
4. Coolant is not continually escaping past the radiator cap from the overflow after a very short period of running even when cold

Then it looks like things associated with the head & head gasket are not the offending area to be looking for coolant getting into the oil.
So I see no point in doing a compression/leak down test now, as it will not prove anything you have not already observed.

So pressure testing the cooling system is next to be checking....kit is about $90 from HF/you can make one like I suggested for a couple of $'s as long as you can get a suitable rubber plug seal [home brew shop /Lowes/Home Depot] or borrow a pressure tester from AutoZone or such. Do NOT exceed 10-12psi & that pressure should hold unless there is/are leak/s.

With oil pan off spark plugs out pressurize the engine assy.
Check for leaks with a flashlight underneath/nothing/have someone turn the engine over slowly while looking for coolant leaks.
Also watch there is no coolant on piston tops although clean spark plugs would have indicated this issue.
With the tappet cover off look for coolant up there but most unlikely.

Let us know what you find.

[Cabin Fever]

Did a couple tests on my A1 yesterday. Below are the test results and a summary of what I've found do far.
1. All spark plugs are the same dark tan to black color. None of them appeared to be very clean. In fact, the fuel mixture may be on the rich side.

2. Did a short term (60 minute) and a long term cooling system pressure test (see results below). Occasionally turned the engine while doing the tests. Both tests had a 2psi drop at the beginning of the test and then leveled off. Did not see any external coolant leaks.

3. The coolant level in the radiator did not diminish during the tests. In other words, there did not appear to be any loss of coolant from the radiator.

4. Engine runs fine with no white exhaust.

5. Just a few tiny pinhead size bubbles (about 1 or 2 per minute) seen in the coolant when the engine is warm and revved.

Any comments?

[artificer]

Good news is there appears to be no external or internal coolant leak/s.
Aren't you glad you didn't start pulling things apart.
BUT were the tests done when the engine was cold or hot?
If not hot I would recommend doing so @ operating temperature.
So warm up with the radiator cap off until the thermostat is opened.
This is indicated by dash gauge being constant @ about 180*F or a bit more.
Shut the engine down & re-do your pressure test.

[Cabin Fever]

Thanks, John. Will try again tomorrow when the engine is hotand let you know.

[Cabin Fever]

If not hot I would recommend doing so @ operating temperature.

Ran a pressure test after I warmed the engine to operating temperature. I shut the engine down and started the test.

Results were pretty much the same as the "cold tests." A drop in pressure at the beginning and then the pressure leveled out. I assume some of the drop in pressure in this test was due to the suction created when the coolant started to cool off after shutting down the engine. Just like the suction created when my wife takes hot canning jars out of the canner. The suction created by the cooling vegetables pulls down on the jar lids and seals them tight.

Again, the coolant level in the radiator did not change during the test.