Stock 2000 XJ Classic, automatic
135,000 miles

When the engine is cold there is a significant knocking noise that is, of course, most easily heard when driving at a slow speed out the driveway.

I seems disappear when coasting down hill or other times when I'm not on the gas.

Doesn't seem to be noticeable at idle with the hood up.

Sounds significant, but runs smoothly.

I took to one place and they said they didn't really notice a noise, but they thought I had a bad valve lifter. Took it to the Jeep dealer and they said they didn't hear anything and that nothing was wrong, but I might need a new water pump soon...

Any ideas? This thing has got to last at least until the daughters are out of college and hopefully until I am out of breath.

Thanks

 

flex plate

 

Far from a Jeep expert here, but my 2000 XJ with 118000 miles was running a little rough when cold.
I switched to Rotella T6, an oversized Wix oil filter, replaced the thermostat (the original one had fallen apart...) and since then, it runs a lot smoother, even when I started it at -13 degrees... We are expecting -18 Tuesday night... I hope I do not have to regret my words!

 

I have this problem too in my '97 XJ Country. Usually I let the engine warm up to the first or second notch on my temp gauge before leaving the parking lot/driveway. Is this good or bad for the engine? It can take anywhere from 30 seconds to several minutes depending on how cold it is.

 

other possible knocks water pump could be going take the serp belt off and start that will tell you if it the motor or othyer accesory.also as posted eariler possible flex plate issue

 

Long periods of time idling can be bad for an engine. The combination of lower oil pressure and lower RPMs causes more wear. Besides, its better to just drive. Start your XJ, let her run for literally 1 or 2 minutes to make sure oil is flowing through the engine, and go. Your truck will warm up faster, your tranny will warm up, and the oil will reach its operating temp pressure sooner.

 

Awesome, thank you 1991Jeep Man!

 

This evening when I left for work, I tried waiting a minute or two (instead of the few/several it takes to get it to the first/second notch like I have been) before going. Well, about a 1/2 mile up the road my engine tick/knock became the most pronounced it's been in months. It was never this bad when I let it idle after startup. It seems like it's coming from the forward right portion of the engine (when in the driver's seat). Thoughts?

 

mine does the same thing. if i wait a a few seconds then take off its loud. if i let it warm up for 10m mins its not as loud. so your not alone i have been trying to figure this out for months.

 

You know, I can see how "extensive" idling (whatever that means) can be harmful to an engine, but it can't be as bad as starting up and driving cold with that ticking/knocking that doesn't happen much otherwise.

I don't know if yours does this or not, GG, but the past couple times when I've started it up, waited 1-2 minutes, then driven, the ticking can be heard at low rpms in the first gear, then I'll rev up and it will disappear, only to reappear in the higher gears sounding a little more prevalent.

 

I always let my engine warm up when it is cold out, oil is thick and needs to warm up before I move, just my thoughts. Now when it is cold here( single digits or negative numbers) mine will make a ping type of knock and to cure it I put some water disperser(HEAT addative) and some octane boost(addative) into the fuel, that stops it as soon as it hits the engine. Don't know if it is the same problem your having, but when cold she likes a little cleaner higher octane fuel. worth a shot,it's cheap!

 

I hadn't thought of (or even heard of) water disperser. Thank you, playin4funami. I've done the fuel treatments and they don't seem to make any real difference with the ping/knock/tick (different sounds from the same area depending on how cold it is outside, how hard I run the engine, and how long I let it idle after startup before driving). I'll have to check out the heat additive thing.

 

I should probably go back and edit my original post, but I figure a new one would be better so it is noticed.

It is not good to let your XJ idle for a long time. However, if it is VERY cold (lower 20's and further down), it would be good to let the truck warm a little longer. The problem is that even though this warming gives the oil more time to warm up, it still gives its amount of wear on the engine. The more pronounced ticking and knocking you all are hearing is basically engine components, mostly rocker arms, that aren't getting as much oil to them as they would prefer because cold oil is thicker and has a harder time moving up through the system. My solution to this paradox of warming?

Warm oil on a cold day is preferred right? Go to Amazon.com, and order one of the magnetic oil heaters. $30, and magnetizes right against the oil pan's bottom. The heat it generates contacts and transfers through the oil pan, and then begins to warm the oil. I have noticed a HUGE difference on cold days with this little guy. Attatch, plug it in for about an hour depending on the temp, and then unplug and go.

 

Do you shut your jeep off when you are "idialing" at a stop light? If you dont let your motor warm up when its cold your going to do more damage than sitting at a idle.

 

Obviously I don't shut my Jeep off everytime I hit a stop light. I'm talking about continious idling of a cold engine. And if you go back and read what I typed, I specifically said that the engine needs to sit for a minute or two to allow the oil to flow.