armadillo

98 XJ 4.0 120K original stock.

Somehow the fan clutch hit the radiator and chewed it up, I imagine the motor or transmission mounts let it slide forward but I inspected them with a flashlight and don't see any cracks or rot in the rubber. Is this a common problem?

Being in a remote area and left my phone in my Tundra, I let it cool and limped home, shutting it down when it got to 220 and letting it cool again.

So I put a new radiator and fan clutch in and re torqued the head to 105# (it didn't take much) just for insurance and filled it with water, started and it bubbles and gurgles and surges and makes hissing gurgling sounds in the upper hose when I shut it down.

The Rotella 15w40 looks clean, the coolant is clean green, runs perfect and no smoke/steam out of tailpipe. I guess the head gasket is shot. I'm alone and don't have a remote start to do a compression check which I suppose is the next step. I'll pick one up in Missoula tomorrow.

This Jeep ran perfect for me in the 53K miles I have driven it with the exception of one CPS and last November when I hit a Whitetail buck at high speed and had to replace the fan clutch and radiator (among other things) which I just replaced again yesterday.

I've been reading a lot of old head gasket threads here, do I need to replace head bolts for some reason? I've replaced a lot of head gaskets on gasoline and diesel trucks and we never did that, but my mechanic days are decades past and things are different now. I don't know much about late model vehicles (meaning made in the last 35 years) with their high temps, lean mixtures and electronics etc..

When I get the head off I'll check it with a straightedge for warp and pour diesel in the ports to see if the valves need grinding. There is only one machine shop in this area and they are expensive and not too good, so I hope I don't have to rebuild it.

armadillo

I just did a compression test. All six cylinders have 145 to 150 PSI compression. Thinking about it, I'm not really certain the head gasket is sealing though, because during combustion, chamber pressures far exceed that amount and what little bubbling I'm getting could be getting past the gasket at peak firing pressure.

Thoughts?

XJRed96

Sounds like a head gasket unfortunately. You may want to pull the valve cover off and (if possible) pressure the test the cooling system because occasionally the heads will crack. But you would see evidence of coolant in the oil. And you do want to replaced the head bolts. They started designing bolts so they offer a one time "stretch" when they are tightened and never really offer the same strength after that.

armadillo

Thanks for the reply. I'll go ahead and do the head bolts. Not only the stretch, but the left row are studs with light rust on then to foil torque readings. I don't have a pressure tester for the radiator, also was wondering if it might harm the catalytic converter or 02 sensors to douse them with coolant from a crack in an exhaust port.

armadillo

I got all the head bolts and everything off the head but it won't come loose. Do they glue the heads to the block at the factory? I got a 4x4 timber and an 8 pound sledgehammer and thumped it around but it won't move.

When (if) I put the head back on, am I supposed to use some kind of sealer like copper coat on the head gasket?

XJRed96

Never use any sealer on the head gasket make sure the block and head are bone dry and clean.

Larry's XJ

Double check that all head bolts are out. Maybe hold new gasket somewhat in place above head to compare holes.

I have seen conflicting info on head bolts. Some say one time, others said you mark with paint so they aren't used a third time.

DFlintstone

It does sound like you somehow missed a bolt. (and agreed, no never use sealant on a head gasket). Bolt's can be used twice. You are suppose to put paint on the bolt head so the next guy will know it's re-used. Be sure to put sealant on the threads of the one that pokes into the water jacket.

Yep, diesel and a straightedge. And now with variable speed reversible drills handy, a piece of fuel line from the valve stem to the drill and some compound for lapping.

Sorry about your bad fortune. My mounts are shot (on one 90) The engine rides a little forward. To get the E-fan out I need to remove the air-box so I can get a bar down to the mount and pry the engine back an inch. You might do likewise to check yours. Remove the air cleaner and get a bar down there and see if you can move the engine in the mount. Just a thought.

armadillo

Thanks for the replies. I got the head loose. The pattern on the head gasket shows the water jacket areas creeping out beyond the openings, but nothing real definitive. Since compression was theoretically getting into the coolant and not the other way around, it seems likely that no coolant trail would be evident. I pulled the oil drain plug and found no coolant.

Lapping the valves seems like a good idea, but I don't have a valve spring compressor. Maybe I can figure out a way to use a big C clamp or something. I checked it with a straightedge and couldn't get 3 thousandths in anywhere. I pulled out the left motor mount and it does have cracks that I couldn't see before.

armadillo

I managed to get the #1 exhaust valve out using a C clamp. The seat has pits almost 1/16" diameter so off to the machine shop she goes. Looks like they did a one angle valve job at the factory.

armadillo

Well I got it back together and running perfect. I replaced the transmission mount and both motor mounts. The harmonic balancer was wobbling so I replaced that too and the timing chain and water pump while I was at it.

So I went to Missoula and the first time I slammed on the brakes, the engine moved forward enough to hit the new radiator and there was steam all over the place. Towed it home, $150.

The clearance between the fan clutch and radiator is a little over a half inch.
I'm thinking that the sheetmetal around the radiator (core support?) got pushed back slightly when I hit a deer last year, although there is no visual indication of it. I think I will try to push it forward a quarter inch and maybe rig up some kind of safety cable to prevent the engine from lunging forward.

DFlintstone

Well great! And bummer Maybe look at another 98? My 90, (the one with good mounts), has at least 2 inches. It IS different though.

armadillo

Maybe the engineers decided that a closer gap between fan and radiator meant more positive air flow. Hopefully someone with a 98 will chime in.

armadillo

The radiator I just put in is a two row core rather than a three row like the last two radiators. Now I have enough fan clearance. I wish I knew this the first time I replaced the radiator, as they have caused me lots of problems.

Now I'm having a heck of a time trying to get the fan shroud for the belt driven fan adjusted to where the fan doesn't rattle it when the engine torques over. The shroud is too small and not adjustable. If the fan axis were centered between the motor mounts like a conventional truck, it wouldn't be an issue.

Have any of you had any luck running these Cherokees without that fan shroud?