Started without coolant, now coolant in oil. Blown head gasket? -
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post #1 of 7 Old 12-24-2009, 12:55 PM Thread Starter
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1998 XJ Cherokee 
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Started without coolant, now coolant in oil. Blown head gasket?

I recently purchased a 1976 Jeep CJ5 258 4.2Lthat needed some work. The front pulleys, water pump, timing chain cover, radiator and alternator were all removed. I was told it had timing problems.

I checked the timing and removed and replaced the chain and sprockets, installed the new camshaft bolt with pin and spring and put it all back together. After putting everything back together I decided to run a coolant flush through the system. With cold temperatures I wanted to be sure it would run before putting an almost completely water based flushing agent in the system that could freeze so I tried to start it with little to no coolant to make sure it would run to complete the flush. After turning it over some off and on for 10-20 minutes, I realized the PO had the distributor 180 degrees out. After fixing the distributor I got it to start and ran it for about 30 seconds adjusting the distributor timing. I then shut it off and put the flushing agent and water in and ran for 20 min before draining and flushing with a garden hose. Finally, i shut it off and filled with a 50/50 coolant and water mix. it started and idles and runs pretty good.

I checked the oil and noticed it looked milky and was above the fill mark. When I purchased it, I drained the oil that was in it and it was completely black. (no coolant) Do you think my starting it without coolant would have overheated it in that amount of time? I ran a compression test of the cylinders and got the results (1-6) (135 140 140 140 135 135) taken with the engine warmed up and using the final pressure from the gauge after the 4th compression stroke. Also I am not sure if it has a faulty oil pressure gauge but it is reading 80-90 but seems to flutter just a bit.

Do you think it is likely a blown head gasket?
Cracked Block?
Other ideas before pulling the head?

Any help would be appreciated. Also let me know if I can provide any other important info I may have left out.

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post #2 of 7 Old 12-24-2009, 01:45 PM
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Sounds like a head gasket or cracked head / block

If you only ran it for a short while you did no damage. An engine will run for five or even ten minits at idle before you have to worry. Mostly heat dammage is caused by a load and no coolant. If you think about all the times somebody has gotten an engine really hot boiled the coolant out of it and still gotten away with it I dobut you caused the problem.
Sounds to me like this is an opportunity to learn to take a head off and see what is up with that engine.

1st. I would try to see if the coolant system will hold pressure with a radiator tester.
2nd. Pull all the plugs and see what they look like. This may give you a clue if the head gasket is leaking into the combustion chamber.
3rd. If you are running antifreeze check for puffs of white smoke and the sweet smell common to coolant leaks.
proper diagnosis is sometimes difficult but not impossible. anybody else out there with a lot of experience with the 4.2???????

Good Luck
Marty SW.
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post #3 of 7 Old 12-24-2009, 03:03 PM
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1. Sounds like a blown gasket the compression is 10 low on the 140 and 15 on the 135. I'd sure check that before I pulled the engine and looked for a crack in the block. 2. Unless you are using a reliable direct reading gauge you really don't know the pressure.
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post #4 of 7 Old 12-24-2009, 03:09 PM
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It does sound like a head gasket problem, same thing with the milky oil is what i got with the 84 cherokee. What i ended up doing, since i was on a budget was up some Alumi seal stop leak(small flakes), and it actually sealed the leak in the head gasket!! I would try a cheap fix like that before any extensive repair..just my 2 cents, good luck
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post #5 of 7 Old 12-25-2009, 07:46 AM
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Its either a head gasket or you have a cracked block or head.

95 xj bone stock for now
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post #6 of 7 Old 12-26-2009, 07:00 AM
Mike Romain
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A gent in here recently blew his block by not mixing the coolant with the water that was stuck in the block after a flush. I also blew my new rad at it's top by topping it up at the wrong time with water in the real cold, it froze before the engine could start.

You also have to figure the block and heater core can hold about 40% pure water in them after a flush so if you top them up with 50/50 mix, you have almost no freeze protection. That 50/50 mix junk they sell is only good for topping up, it is no good to use after a flush.

I always use the correct amount of pure antifreeze first, then I top it up with water and can only usually put a quart or so water, the rest of the water was hiding inside.

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post #7 of 7 Old 12-26-2009, 07:22 AM
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Cranking and running the engine without water for short periods of time will not hurt it. The problem you had was probably there before you ever started working on the engine.
I used to race dirt track cars with SBC engines. When we rebuilt an engine, we heat cycled it without water about four or five times to seat the rings. We would start it up without water and run it until the block and heads got hot enough to the touch that we could not put our had on it, shut it down and let it cool and then do it again. Those engines were set up loose, but it won't hurt a street engine unless you let it run a long time without water.

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