Does new TB stress WP?

[artbuc]

A friend has a 1998 Camry with the V6 1MZFE engine & 68 k miles. He is replacing TB based on time, not miles. Dealer told him he should replace WP because new TB will over-stress the old WP and make it fail. This is definitely not my experience and I have not heard anyone else offer that advice. I believe the forces acting on the WP are determined primarily by the hydraulic tensioner. What do you think? Thanks.

 

[Mud]

Not sure on a Camry but on Audi 1.8 or other cars where the timing belt drives the WP, I replace everything. Too much of a pain to get in there again.

 

[Astro14]

There is a belt tensioner, right? so new belt, old belt, it's all the same stress...but I would change it, for the reason Mud mentioned...takes me about 4 hours to do a WP that's behind a TB...with 168K on it, the WP is nearing the end of a normal life anyway...

If the car had, say, 90K on it, I would skip the WP...but with this # of miles, just change it and save yourself the coming hassle...

 

[bluestream]

Pump, timing belt, idlers all get done at once

 

[bdcardinal]

It is general practice to replace a water pump when you do a timing belt. When I had it done on my Volvo, the tech said he does not do them because they don't go bad, which I have heard numerous times on R cars, at least for the first change. When he opened mine up he said he saw signs of coolant seepage so he replaced it.

 

[artbuc]

Originally Posted By: Astro14
There is a belt tensioner, right? so new belt, old belt, it's all the same stress...but I would change it, for the reason Mud mentioned...takes me about 4 hours to do a WP that's behind a TB...with 168K on it, the WP is nearing the end of a normal life anyway...

If the car had, say, 90K on it, I would skip the WP...but with this # of miles, just change it and save yourself the coming hassle...


Only 68k miles, not 168k.

 

[Astro14]

Originally Posted By: Bluestream
Pump, timing belt, idlers all get done at once


Depends on the car, really, and the PITA factor on changing vs. the reliability of the WPs. I change the belt, tensioner and idler at the same time on my Volvo "white" engines, and previous cars with that engine ran until the second TB, at which point, I changed the WP. So, I skipped the WP on the two Volvos in my sig...time will tell if that was a good decision.

But I would replace the idler and tensioner as suggested...

 

[artbuc]

I appreciate the responses but I am not asking about the pros/cons of replacing the WP while you are already in there doing the TB. I am asking specifically about how/if a new TB affects the life of the old WP. My thinking is that the forces on the WP are determined by the hydraulic tensioner. IOW, the WP doesn't know if the TB is new or old. Is that correct or does the stiffness and/or the path of the neew TB apply different stresses on the WP leading to premature failure?

 

[yonyon]

The new TB should not increase pressure on the WP unless the old TB had stretched enough that the hydraulic tensioner was unable to maintain sufficient tension. Low tension can produce a sort of rattling noise behind the timing cover. I wouldn't expect that at such low mileage, but considering the age wouldn't be too surprised either. If you have no such noise the tension is probably fine at this time and won't increase from putting a new belt on.

 

[artbuc]

Originally Posted By: artbuc
My thinking is that the forces on the WP are determined by the hydraulic tensioner. IOW, the WP doesn't know if the TB is new or old. Is that correct or does the stiffness and/or the path of the neew TB apply different stresses on the WP leading to premature failure?


Been thinking about this some more. I believe my conclusion is correct but for different reasons. In a static, frictionless system, the forces on the WP pulley would be determined by the hydraulic tensioner. Not so in a dynamic system with a toothed belt. The lateral forces on the WP pulley will be determined by tension in the TB between crankshaft and Bank 2 camshaft pulley. This tension is determined by the forces required to rotate Bank 2 camshaft pulley. Obviously, greatest tension occurs at start-up. If the TB stretches, the hydraulic tensioner will take up the slack on the non-driven part of the TB and the relative positions of the crank and cam shft pulleys will change, but the load on the WP will not change. I do not believe the WP can tell if the TB is new or old.

 

[artbuc]

Edit: TB tension at WP pulley determined by forces required to turn both camshaft pulleys (I think, lol).

 

[mechtech2]

A good reason to do a WP with a TB is because of location.
You will have to do the work all over again in some instances , so it is smart to do the WP at TB change time.
BTW,it is nonsense about the new belt causing WP failure.

 

[yonyon]

Good point artbuc. So then the only things that should increase the forces on the WP pulley would be:

-A change to the valvetrain such as a new cam or springs.
-A change that allows higher maximum engine RPM
-A change (usually a problem) that gives a lower idle RPM
-A rough running condition

 

[artbuc]

Originally Posted By: mechtech
BTW,it is nonsense about the new belt causing WP failure.


I got a real good laugh out of this statement. When my friend asked me what I thought about the dealer's statement, my exact words were "That's nonsense".

Since my friend puts less than 5k miles on this car a year (all short trips close to home) and the WP is probably good for at least 180k, he will be getting rid of the car long before the WP goes bad. Of course anything can happen, but if I were him, I would not pay for a new WP. I did replace the WP on my 99 Avalon because the bearing felt a tiny bit sticky and I was doing the job myself. A regular poster on a Lexus forum is an absolute mechanical genius. He cuts apart old parts, eg TB idler pulley bearings and WP seals, just to see how well they are manufactured and if they were getting close to failure. He actually miced each ball bearing in the idler & tensioners pulleys. He said the seal on the Aisin WP's in these 1MZFE's was the best design he had ever seen on an auto WP and believed they are built to last the life of the car.

 

[SteveSRT8]

ABSOLUTELY replace that WP while it's apart. Not just on the basis of miles but also for time.

It is ridiculous to do all that work and leave the old WP on. Sure the belt won't actually cause a failure but the jostling and yanking around, even the unloading can change the way things have worn together and accelerate failure.

 

[artbuc]

Originally Posted By: SteveSRT8
ABSOLUTELY replace that WP while it's apart. Not just on the basis of miles but also for time.

It is ridiculous to do all that work and leave the old WP on. Sure the belt won't actually cause a failure but the jostling and yanking around, even the unloading can change the way things have worn together and accelerate failure.


I respect your opinion. Where do you stop when working on an older car? I am in the middle of replacing valve cover gaskets on my 99 Avalon. I decided to go ahead and replace the No 1 Coolant By-Pass hose while I already had the air plenum off. I know that hose will most likely outlast the car but I am going to do it anyway for peace of mind. Will cost $13 for the hose and $45 for the intake manifold gaskets (OEM only here). Then I considered replacing the Bank 1 injectors because I already had Cyl #2 injector fail last summer. I decided against the injectors. 3 years from now I may be happy that I saved myself a few hundred bucks but, OTOH, I may be kicking myself next week when Cyl # 3 injector [censored] out.

 

[The_Eric]

Originally Posted By: SteveSRT8
ABSOLUTELY replace that WP while it's apart. Not just on the basis of miles but also for time.

It is ridiculous to do all that work and leave the old WP on. Sure the belt won't actually cause a failure but the jostling and yanking around, even the unloading can change the way things have worn together and accelerate failure.


With only 68k miles on it, I'd be surprised that it needs replaced, especially with the long life coolant that's in there.

I'd also be tempted to leave it on, because the pump the garage will put on is likely to be an aftermarket pump, which are complete junk! I've seen numerous pumps come back leaking (including my own, personal car). It's MUCH more rare to have an OE pump leak (barring some bad designs or pumps made with defective parts).

IF the o/p's friend decides to have the pump changed, the only way I'd recommend to go is to use an OE pump OR a pump from the OE supplier such as Aisin, NPW and so on.

 

[SteveSRT8]

Originally Posted By: artbuc
Originally Posted By: SteveSRT8
ABSOLUTELY replace that WP while it's apart. Not just on the basis of miles but also for time.

It is ridiculous to do all that work and leave the old WP on. Sure the belt won't actually cause a failure but the jostling and yanking around, even the unloading can change the way things have worn together and accelerate failure.


I respect your opinion. Where do you stop when working on an older car? I am in the middle of replacing valve cover gaskets on my 99 Avalon. I decided to go ahead and replace the No 1 Coolant By-Pass hose while I already had the air plenum off. I know that hose will most likely outlast the car but I am going to do it anyway for peace of mind. Will cost $13 for the hose and $45 for the intake manifold gaskets (OEM only here). Then I considered replacing the Bank 1 injectors because I already had Cyl #2 injector fail last summer. I decided against the injectors. 3 years from now I may be happy that I saved myself a few hundred bucks but, OTOH, I may be kicking myself next week when Cyl # 3 injector [censored] out.


You make a great point. I just hate to see it get screwed up after the hard work you already did!