troyatl

ok so i believe i have a blown head gasket. the last 2 times i drove her she has overheated after only 10 min of driving, the idle sounds weird almost like an 60's ford truck and black smoke comes out of the exhaust. is this a blown head gasket???

are there any test to run to make sure thats whats wrong.

wjnfirearms

Several things can tell you if the HG's blown.

1. Coolant in the oil. Looking at the dipstick is a dead giveaway. More commonly a cracked block or head, but can happen with a bad HG.
2. Exhaust in the coolant. Have a shop with an emission tester hold it in the radiator filler neck. If the machine gets CO readings, conclusive. Usually shows by bubbling into the overflow bottle and overheating.
3. Look at the spark plugs. If the plugs show signs of fluids getting into the cylinders, conclusive. Also could be valve, head or block issue often more commonly.

Overheating can be easily due to a bad thermostat, radiator obstruction or just too low coolant level. The black exhaust is not due to a bad HG unless you are getting a lot of oil in the cylinders. Usually oil smoke is bluish and smells like oil to a degree. More commonly, oil in the cylinders is due to bad valve seals or bad piston rings. One quick and dirty way to see if the overheating is due to a head or HG issue is to remove the thermostat and reseal the housing so it doesn't leak. Run the Jeep and see what the temperature does. If it still heats up badly, you have a blown HG or more serious head issue. At that point, depending on how many miles the engine has on it, you'd either be considering a good used motor or a rebuild.

knuckleduster271

When my hg blew I was just mysteriously losing coolant, no sign in the oil or the cooling system or any white smoke. It would get low and I would have to top off the cooling system every 4-5 days. After about a month it started to overheat more than usual. that's when I found coolant in the oil. My hg blew in between cylinder 3 and 4. I opted for a new head as it was only $260 and I wasn't sure of mine had cracked or not. Better fix it soon or you will toast all your internal bearings

troyatl

ive been running water for coolant because it keeps over heating so should i look for watery oil on the dip stick??

BuckB91XJ

1.) Overheating or losing coolant is the most obvious.
2.) Oil in coolant.
3.) Coolant in oil.
4.) Cylinder compression leak down.
5.) Engine missing while running.
6.) Lots of white smoke (water) in exhaust.

I think I got most of them. I'm sure I will think of more.

troyatl

i got 4 and 6...FML but it was white smoke but now has slowly turned into blackish smoke

tjwalker

Get a compression test done on all cylinders pronto.

This is what a shop would do as job #1.

It very well may tell the story.

The spec is 120-150, with no more than a 30 psi variation between cylinders.

connman

ok new aluminum radiator 3 electric fans all work 180 thermostat good hoses water pump moving water no oil in water, no water in oil, no white smoke, temp shoots 250 in a few at 55 or more, pull over and idle back to 210 in about a min, runs at 210 on streets any advice

Radi

^^ This. Head gasket isn't the only thing that could cause your symptoms, do this as a starting point so you'll know which way to go.

Firestorm500

Head may be cracked internally.

Black smoke is usually a rich condition.

Parsnip

New tsu is my guess. Verify temp with a ir thermostat

Parsnip

Domt do that!!!!! Always have.coolant.mixed with water 40/60 mix minimum or you'll rust your block internally

thomas maniaci

So i did a compression test and these where the numbers i got. This is from a 1994 jeep xj. Would these numbers be considered normal?

Zingo

That looks okay. Do all the plugs look good and the same?

Also how do so many threads from years ago magically come back? Lol

kaasmosis

Ever resolve this? I’m going through the exact same thing.