4.0L and nasty sounds

Hey,

Winter is upon me in lovely Potsdam, NY. It's been in average about teens or single digits. Anyways, when I start my Jeep it's got a loud clacking or tapping sound coming from engine. The sounds go away after I run it for a while, usually I let it warm up for a good 5 or 10 minutes at least before I drive it. It's an 88 all original never been rebuilt 127,000k on it. I assume it's piston slap, cuz the metals have different tolerances in the cold. That or it's a wristpin knock from low octane gas. Any info would be appreciated ahead of time,

Thanks,
Majo

My guess would be piston slap. Maybe a block heater would help? I don't know if they make one.

pancake said:

My guess would be piston slap. Maybe a block heater would help? I don't know if they make one.

Click to expand...

Perhaps piston slap, normal in many XJ's. Might also be noisy lifters. Like me, they don't like the cold weather. Be sure you are using a winter oil, such as 5w-30, or even better synthetic oil.
Yes, I can assure you, they do make block heaters for XJ's. I've never needed one, even in the cold winter temps we get here.

I wouldn't worry too much about the piston slap. Mine has 190,000 miles on it and has had piston slap since 110,000.

CUxj88 said:

Hey,

Winter is upon me in lovely Potsdam, NY. It's been in average about teens or single digits. Anyways, when I start my Jeep it's got a loud clacking or tapping sound coming from engine. The sounds go away after I run it for a while, usually I let it warm up for a good 5 or 10 minutes at least before I drive it. It's an 88 all original never been rebuilt 127,000k on it. I assume it's piston slap, cuz the metals have different tolerances in the cold. That or it's a wristpin knock from low octane gas. Any info would be appreciated ahead of time,

Thanks,
Majo

Click to expand...

My 88 with 165k does the same thing. It is noisy lifters, Use a lighterweight oil and the problem should subside.

PS, they do make block heaters for the 4.0, I have one on my 88MJ, don't necessarily need it. But, heat within 30 seconds of starting on a winter day is nice.

its most likely the lifters and the rest of the valve train rattling until it gets sufficient oil.. piston slap is a possibility, my experience with piston slap was with a partially warm engine , never heard it when cold or hot.. i really doudt it is anything related to spark-knock since it happens at idle and goes away when it warms up.. use a thinner oil. is this only related to the cold weather? nothing in warmer temps? thats most likely the problem. a block heater might help this by keeping the engine and oil warmer... i have seen some that replace a freeze plug in the block and also some that epoxy a heating pad to the side of the oil pan... might be beneficial to run synthetic oil this time of year too......
mike

Thanks for all the feed back, yeah i'm runnign 5w-30, no synthetic....may give it a try when I get home. Block heater is outta question, I don't think my university would let me bum power off them like that or run extension cords 200 yards to parking lot hehe, I just sweatin it cuz last year temps got down to -43 , in fact it was colder here in Potsdam one day then it was at the North Pole, true fact. Anyway I'll just run it till it breaks then replace it, if it breaks it was meant to be replaced anyway.

It's pretty darn hard to break a 4.0. They run without much oil, water or care.

maybe think about using remote mounted deepcycle battery to run an AC/DC inverter to power the block heater... it would take some research to find out amperage draw and whatnot but if its that important it might be worth at least looking into... just a spur-of-the-monent thought without much thinking put into it.. may not be that good of an idea but i'll throw it out at ya anyways..
mike