95 lots of blow by and detonation hothttp://www.automotiveforums.com/vbulletin/images

[95xj]

I have a 95 cherokee 4.0l auto with 218k miles. I just bought this and runs great till it gets hot, then lots of smoke coming out valve cover. Then you gets a little top end rattle (detonation) on #1 cyl. Pulled plugs they are all worn bad (plugs 2-6 are clean looking) but #1 is the worst. The jeep only has idiot light on the dash for temp, so im going to try cooler thermostat and new plugs. The thing has alot of pep, so i was thinking might not be head gasket which is my only other idea at the moment. Has new water pump and radiator. Have yet to do compression check yet. Any help is much appreciated.

[rhandwor]

Do the compression test if readings are low pump oil into the cylinder. If the compression comes up a lot you need a rebuild engine.

[fredjacksonsan]

I'd also consider changing the cap, rotor and wires along with the plugs.

The hot thing is troublesome and although the engine could be done like rhandwor suggests, I'd make sure the cooling system is good...water pump, thermostat, radiator. On an older vehicle that has not been well maintained your radiator can be blocked enough to let it overheat.

There are several threads on overheating XJs in here...and since it runs fine while cold that is where I'd look first. The detonation is when it gets overheated IMO.

[95xj]

Also, just noticed there was no fan shroud. Will this cause the overheating and top end rattle. I'm going today to get a temp gauge to see actual engine temp.

[fredjacksonsan]

Fan shroud will help by increasing airflow...it doesn't overheat while driving on the highway you'll need a shroud. But I'd bet on a new radiator.