olliedog

Hi there. I`m going to sound thick here but i have just bought a UK... year 2000 jeep cherokee 2.5 turbo diesel with no service history, but other than a very slight oil leak (3 drops a day off the engine somewhere) and i think a front right wheel/hub bearing need replacing...it seems a good thing. But to make sure it dont break on me i really really hope someone could tell me if this model has a timing belt or chain. I see that it has a thick multibelt at the front but was hoping it has a timing chain so that it doesent need changing, because if its a timing belt then i will get it done asap to be safe. I hope someone can help out here as i only bought it yesterday and i would rather be safe than sorry.
Thanks so much to anyone who responds to this.
ollie

5-90

If it's the AMC gasoline engine, it's got a chain. AMC never did an engine using a timing belt.

jd4x426

the amc motors are chain driven but im not sure about the deisels

Uncletruck

If its the 2.5L turbo diesel made by VM Motori for Europe issue Cherokees, it has a timing chain, not belt. But from what I have read, it's timing chain was one of its weak points.

-UT-

okcjeeper

Also remember even timing chains need replacing and can stretch and loosen over time they just last longer then belts.

findaname

It is really amazing just how much confusion there is about this. I get the idea that Chrysler have produced this motor with both chains and belts, throughout the 11 or so years it was in production.

I had to replace the engine on my 1998 Sports XJ - unfortunately. I asked the foreman of the authorized Jeep workshop here in Norway to change the timing belt on the old replacement motor which they were putting in for me. He replied that there was no timing chain/belt on this model. It was all done by vacuum

Well, what I belive he meant was that the only timing arrangement is the externally mounted belt, which drives the steering pump, the dynamo, the a/c compressor, etc. etc. I believe that internally, the valve timing is managed by a vacuum system. This means that there is no real danger of anything going very wrong if the external belt should fail. You simply put on a new one.

This is my assumption and I would appreciate comments - hopefully which confirm my assumption

5-90

Hah?

I've not heard of vacuum being used to affect anything more than ignition timing - even on Variable Valve Timing engines, it's being done by solenoids or stepper motors running the camshaft back and forth (and the cam having a tapered grind on each lobe.) There's talk of eliminating the mechanical coupling between camshaft and crankshaft - and the camshaft - altogether, and just using solenoids to open and close the valves directly. This would be controlled by ECU programming instead, would effectively eliminate the "opening ramp" and "closing ramp" of the cam lobes (leading to more effective duration and more valve flow volume,) and the elimination of a number of wear items in the engine - at the expense of greater electrical complexity. I shall reserve judgement.

The accessory drive belt, being exposed, isn't the greatest thing in the world to use for a timing drive. Moreover, you must have positive engagement in order to keep accurate cam/crank phasing, this is why timing belts have the transverse ribs on them that accessory drive belts do not (it doesn't matter if your alternator or your power steering pump slips a bit. it can matter a great deal if your camshaft should slip a bit in relation to the crankshaft!)

As far as variations in production - the factory production of the AMC engines (4-150 through 2002, 6-242 through 2006, V8-360 through 1991) was essentially unchanged from AMC specifications - save for relatively minor revisions (cylinder head port arrangements, block webs, addition of a main bearing cap brace.) Therefore, the timing chains stayed - in all three engines.

The only way there could be no timing chain or belt whatever would mean that the camshaft and crankshaft have to be directly coupled by a gear drive (either directly, with the two shafts spinning in opposite directions; or using an idler gear, with the shafts spinning in the same direction.) The IHC four-cylinder was a good example of this, as was the VolksWagen air-cooled horizontally-opposed four-cylinder and, I believe, the Nissan Diesel as used by IHC. (More examples are extant, but those are the ones that come to mind.)

Aftermarket gear drives have been made for various engines - SBChevvy, BBChevvy, various Fords, and I think the LA- and RB-block Chrysler. The AMC six also had a gear drive available - but they're about as common as hen's teeth. Aftermarket belt drives for "Big 3" V8 engines are also extant, but tend to be recommended for racing use only (where the engine is going to be torn down and inspected a minimum of annually, with wear parts replaced as a matter of course. And where critical fastening screws are considered 'wear parts'...)

Also, the only example I can think of where an "accessory" is driven by a timing belt is on some Mitsubishi engines used by Chrysler (maybe on some other Japanese engines as well,) where the water pump is driven by a cogged pully engaged with the inside of the timing belt - an idea I'm not so wild about. If the water pump fails, you have to tear down the whole front of the engine and make sure that you don't screw up the timing! What are you supposed to do - replace the water pump whenever you replace the timing belt as PM? Thank you, no. Almost as bad as a crankshaft-driven oil pump mounted behind the timing set - yech.

In the absence of any information to the contrary, I'm inclined to think that the "foreman of the Jeep-authorised repair shop" to whom you spoke was talking through his hat...

findaname

Thanks. I am really very grateful for your quick and very plausible, knowledgable and amuzing response. I am also very pleased to learn that I have a chain on my XJ. I was not at all comfortable with the idea of a vacuum linkage with the driveshaft. Sounded a bit fuzzy. Good luck to you.

5-90

Wait - "vacuum linkage with the driveshaft?" I don't think he was talking through his hat on that one - perhaps an orifice most of a meter lower? The only thing even close to a "vacuum linkage with the driveshaft" would be the vacuum-actuated Central Axle Disconnect found on mid-model 4WD vehicles (which is a silly idea - and usually gets abandoned anyhow.)

I've long favoured timing chains - can't stand even the idea of a timing belt on a production car. When we were car-shopping for my wife, there were a few things that sold me on the Verona we ended up getting...

- Two-year-old car with three hundred miles on it (it was a loaner that they'd gotten right before they quit doing loaners.)
- Four-door sedan (got grandkids.)
- Inline six engine (even if it is jammed in crosswise...)
- Single roller timing chain setup (!)
- Enough power to get out of its own way
- Comfortable for long driving trips
- Fits both of us (I'm 6'3", she's 5'2". Makes it a challenge...)

I'm not strictly wild about the ABS, I need to disable TPMS, and I'd rather be quit of the airbags (best way to not get hurt in a roads incident is to not get into one!) but those are more irritants than anything else. I'm also happy that the vehicle hasn't succumbed to the "feature creep" that I see in so many "modern" vehicles - as I've said before, every time I see a new vehicle loaded down with drive-by-wire and assorted unneeded creature features, I just want to get (and restore) a 1947 ****** or something...