Replaced head gasket but still have a problem

luca1014 · 11-06-2008, 10:03 PM

Hi everyone,

I have a 1999 WJ with a 4.0 that had a blown head gasket. This is the first time I have done a head gasket but I'm pretty mechanically inclined and I had the service manual so I attempted it. I finished everything step by step. I started her up for the first time and it ran no problem.

I noticed the coolant got low so I topped it off thinking that it was just the thermostat opening. I drained the oil and noticed it was still milky but i figured maybe it was the left over oil-coolant mix from the blown head gasket. I refilled the oil again and let it run for 15 min. I let the fan cycle on and off a few times then drained the oil again. I noticed this time it was even more milky. This time it had the viscosity of coolant. I checked the coolant and there is no oil in it.

So what did I do wrong? Is there something I could have missed? I made sure I coated bolt number 11 on the head with sealant and everything was torqued down to what the service manual said. Any ideas? Thanks in advance.

kmd1776 · 11-06-2008, 10:34 PM

did you get the head checked for flatness?? crack in the head? crack in the block or corroded water jacket??

dickensheets · 11-07-2008, 07:24 AM

What he said.

I would pull the head again and take it to your local automotive machine shop for cleaning and surfacing. They inspect it for warpage. This is important if the vehicle ever overheated in the first place. Blocks don't tend to warp as they are more substantial in build. The head is thinner and less substantial so they can warp easier if overheated. Good luck.

Also use an OEM gasket. The aftermarket ones are cheaper BUT this is a fairly important item.

kmd1776 · 11-07-2008, 07:31 AM

ive done 3 head gasket changes on 4.0's with the blue FELPRO gaskets and never had any problems with them. i wouldn't use a cheap gasket, but there are some really good aftermarket gaskets out there that can be used.

luca1014 · 11-07-2008, 09:54 AM

The head was sent to a machine shop prior to putting the head gasket on. It was machined and checked for cracks and they said it was alright. I used a mopar head gasket, not aftermarket. Can you give me more info about a corroded water jacket? How would I find out if this was the case?

kmd1776 · 11-07-2008, 03:55 PM

im not sure how you can check the block with the engine still in the jeep... i know when i rebuilt my 4.0 the machnist boiled down the block and checked for all this stuff.

im curious if there is some type of pressure test you can run on the block when the head is off to see if there is a problem with the block....

kmd1776 · 11-07-2008, 04:00 PM

did some research and found this:

Quote:

TEST #1: Pressure Tests for the Cooling System

The first test of the cooling system is done when the engine is cold. A cooling system pressure tester can be installed in place of the radiator cap. Pressure in the cooling system and hot coolant are not something to be treated lightly. Use caution, and never remove the radiator cap from an engine that has been run even for even a short time. After installing the gauge, pump it up to 10 pounds. Look around for leaks if the gauge shows any pressure loss. Common trouble spots include heads, hoses, water pump and rear heater core. If you smell something sweet when you turn the heater fans on, it may be a coolant leak at one of the heater cores, or simply the O-ring at the rear heater valve leaking. Because there is often more then one leak in the system, it is necessary to continue pressure testing until the system holds pressure.

TEST #2

Start the engine cold with no pressure indicated on the gauge. The pressure in the cooling system builds to aprox 7 lbs at normal running temps looking around for leaks. But if the pressure builds quickly to around 15 lbs the pressure is coming from one of the cylinders through the inner head gasket. This can also show up as a coolant pressure loss in the first test. In extreme cases the cylinder can fill with coolant, and will not turn over. This is know as hydraulic lock, and if you suspect this pull the spark plugs and tries to turn the engine again. Pulling the plugs from the engine allows water to escape from the spark plug holes.

This is simply a suggestion but the first test is easy to do and will tell you right away where is your leak or leaks is.

looks like there is some hand held pump you can buy to hook up to the radiator cap and measure the pressure... probably will be the easiest and cheapest way to know if you have an internal leak or if you still just have some residue left over in the oil system,