cracked head or blown head gasket?

New guy on the forum. I searched, but didn't find an answer. I'm on my third XJ in ten years, so I do have some experience with them.

I have a 1999 4.0L XJ with 105K miles. Runs fine. Last night I took it to bring a boat home for a friend. No problems driving 90 miles there. He buys the boat, we hitch it up, and after about twenty miles at 55 mph he says "hey, there's a big cloud of white smoke behind us." I pull over, yes there's smoke and a strong smell of antifreeze and my oil is about a quart higher (no milk). But the water temp never got over 200 (the usual) and the engine didn't feel or smell hot. I had it towed home, and when we got here there was water under the Jeep on the flatbed.

So I figured it was a head gasket. I was going to take Friday off work and change it, but then I found this site and started reading about cracked heads. So my question is:

Once I pull the head is there a way to tell if it's cracked without doing pressure testing and magnafluxing? I'd like to get this done in one day, but I'm not sure the shop can get the head done soon enough.

Also, how could this happen without overheating? Sure, the boat put a load on the engine, but I've pulled smaller trailers without a problem.

thanks for any answers,
Dave

It may not be the head. You mentioned there was "water" under the jeep from where it was parked on the flatbed. I would virst verify that no hoses have slipped off, there are no cracks in the radiator...etc etc. The fact there was some sitting on the flatbed makes me think something has come off, so I would look around the engine and make sure nothing has flown off.

However the engine oil being a quart higher does make me wonder.....

A 99 should have the 0630 head on it, which is far less prone to problems than the 0331 that began in the 2000 model year.....this can be verified by looking at the drivers side of the head, right below the bottom of the valve cover, about halfway down the engine. 105K is a little early to be having cracked head / blown head gasket problems, unless it's been overheated badly in the past.

I just checked, and it's the 0630 head. I also checked the oil, and it's right at the full mark, same as when I topped it off yesterday before the trip. I guess I might have been mistaken in the dark and the stress of the billowing white smoke. The oil looks good; it's at 4500 miles. The coolant in the radiator is too low to see.

There was definitely lots of white smoke. There was so much that passing cars were blowing their horn, which is what tipped off Rob. Now I'm starting to wonder if it was really coming out of the exhaust. There was no water dripping out of the tailpipe last night.

Now I'm thinking that I'll look everything over on Saturday, and try to find a leak before I pull the head. Suggestions welcome.

thanks,
Dave

How's your trans fluid? This never caused white smoke for me, but when it was overfilled it would vent out on hot highway summer trips.......it would leave an oily residue on my rear hatch and bumper.

How'd you know your oil was a quart high? If you checked it while the engine was hot it would normally show behing higher-up on the dip stick.....

If your engine temperature didn't go up it's probably nothing serious. Check radiator and hoses and such, and all fluids (including transfer case, differentials)

Start it up and check for smoke. If it's not a external leak, I'd guess it's the head gasket.

You might want to inspect the freeze plugs also.

Dave4.0 said:

Start it up and check for smoke. If it's not a external leak, I'd guess it's the head gasket.

Click to expand...

Jay Welch said:

You might want to inspect the freeze plugs also.

Click to expand...

Thats what i'm thinking....sounds like one might have backed out enough to cause coolant to spew out once it gets good and hot.

Also didn't think of the tranny. You said it happened at night, so are you sure it was white smoke? I've had my transmission run hot and blow fluid out of the breather making a nice little smoke show before at night, and it did appear to be white when I looked at it in my mirror, even though it wasn't. The fact you drove it 90 miles, meaning everything got nice and warm, and then started pullin a boat back, I have to wonder if it got just a little too hot.

Hey, thanks for all the suggestions. They help.

I went out after work today to inspect the engine. I didn't see anything obviously leaking. I sprayed Gunk on the engine and hosed it off to get it clean so I can work on it. I checked the oil again, and it is definitely right where it should be, and it looks clean and not milky. The trans fluid is at the lower mark. I filled it up 4500 miles ago when I changed the fluid and filter. The radiator was only about a half quart low.

I started the engine and ran it for a few minutes, but didn't see any smoke. There was water coming out of the tailpipe, a drop every couple seconds. Is this just normal condensation?

I didn't have time to run the engine for a long time, but on Saturday morning I'm going to top off the trans fluid and radiator, and drive up and down the interstate until I see smoke. In the daylight I should be able to see right where it's coming from. A freeze plug would be nice. If it's coming out the tailpipe I'll do the head gasket.

Oh, I called up my buddy who bought the boat, and he doesn't remember whether the smoke was coming out of the tailpipe or just generally from under the car. The back bumper and liftgate weren't oily.

Dave

The drip drop of water out of the exhaust is normal, mine does it...

I took a 20 mile drive on the interstate after work today, driving 70-80 mph, with one eye on the rear view mirror the whole time. No smoke at all. Engine temperature stayed normal. No burning smell. When I got back everything was normal.

Now I'm really confused. Because there was definitely a big big cloud of white smoke following me down the highway on Tuesday night.

I guess tomorrow I'm going to change the oil and filter and flush the radiator, and just keep a close eye on it for a while. And not tow any more boats.

Could this be a real small head gasket leak, that only becomes apparent under heavy load? Because usually mechanical problems don't just go away.

Dave

If you have any doubt, it's worthwhile to get the cooling system pressure tested. That should tell you in pretty short order if there's any place for coolant to leak out.

I'm really starting to wonder now if it was the transmission that overheated, and was blowing tranny fluid out of the breather onto the hot exhaust.

How heavy was the total load you were pulling behind the Jeep?

What is the condition of your cat?

I was driving on the Masspike last summer at 70-80 and I started seeing white smoke, at the time I had idiot gauges so I pulled it over, thought it was overheating but couldn't find any problems problems

Slowed it down to 65 ish till I could get to an exit and the smoking stopped, looked under my Jeep and it was the cat that was smoking, drove slower and replaced it when I got home

Just something else to check

I liked the suggestion to pressure test the cooling system. I couldn't find a pressure tester at an auto parts store this morning, so I made my own. I hacksawed a Schrader valve off an inner tube, and zip tied it into a short piece of tubing I put the tubing on the overflow connector of the radiator filler with a hose clamp. When I put a bike pump on the valve I found that the radiator cap was actually blocking the overflow hole and not letting air into the cooling system, so I used a C-clamp visegrip to push the top of the radiator cap down so it would seal and let air into the cooling system.



The pressure gauge on the bike pump is not accurate, so I used a digital tire pressure gauge to find that 25 psi on the pump meant 16 psi in the real world. The radiator cap said it holds 16 psi. I pumped the system up to 25 psi indicated and left it for 30 minutes. It didn't leak any pressure. So maybe I don't have a head gasket leak.



I also flushed the radiator because it was pretty dirty, and changed the oil and filter because it was time. I drove the car around for the rest of the day with no problems. I'm going to keep a real close eye on it, and watch for white smoke.



Thanks for the suggestions.

Dave

The best way to check this out is to do a hydrocarbon test on the radiator. There are kits you can buy or you can have a mechanic do it. To do the test you pull the radiator cap and the tester sucks in the "air" coming from the radiator. If there is a leaky head gasket, hydrocarbons will have been forced into suspension in the antifreeze. As the "air" is sucked into the tester, it bubbles it through a test liquid. If hydrocarbons are detected, the fluid changes color.

There's 30 PSI shown on that gauge.

Also that's some nasty crap you found in your radiator.....eww!

Ok my turn... 2000 XJ 4.0 Auto 71000...as of about last month i was getting low on coolant so i added almost a whole gallon, started again on monday temp shoot to 260 and i'm low on coolant in the reserve tank, i've been watching and i have NOT leaked anywhere. so i pulled the oil filler cap and she was foaming at the mouth when i pulled it off after the XJ had been running and the temp shot to 260... so what should hope for head gasket? i know it is either the head or the gasket itself, anyway to check since it is not leaking on the ground that i can see, and the oil on the dipstick is higher then prior checks.

That crap came out of your radiator??? eeeeeeewwwwwwww

Did some of that crap under the cap. If so it would have allowed the water to push out through the overthrow bottle.

Yeah, make sure the sea ling surfaces are squeaky clean.