1HD-T timing belt tension, is this normal? (1 Viewer)

[torqueluvr]

Took the timing belt off today to get the injection pump out which needs rebuilding/resealing. I noticed the tension on the timing belt was pretty loose. Is this normal? If not, would it affect pump performance? Also, the belt was off the pulley by a 1/4 inch I'd say.

I have a new belt kit, tensioner, spring etc etc on order so I'm replacing it anyways. Just curious if this is normal.

92 HDJ81, 274K. This belt has about 80K on it, from what I can gather from the previous owner and my km I've put on the truck.

 

[roscoFJ73]

Looks a bit old. Previous owners have a bad record on this. But they can last 300000klms or more. There are few vidoes on you tube about replacing them, you can see what they should be like from them.
It wouldn't have been affecting pump performance, it probably wouldn't have run too well. But there was a danger of it coming off.
If you are on the original water pump, you might want to do that while you are there. I've had 2 go at around 250000klms.

 

[mudgudgeon]

No, I'd expect it to be a little firmer than that.
It will bend a bit when you push on it, but definitely shouldn't feel loose.

It can't affect the pump, pump is gear driven, timing belt is driven from the pump gear, not the other way around.

It would probably have an effect on cam timing just because worn teeth on the timing belt can retard cam timing by a few degrees.

The biggest problem is the potential for the belt to come off, or slip a tooth. Both could be disastrous.

 

[FJ73Texas]

I took my timing belt off my 1PZ so I could remove the IP as well. It was on pretty firm and it didn't appear to be slipping off at all. I have about 20K more KMs to go on it before it needs to be changed but decided to get a new belt anyway while I have it all torn down.

 

[dan1554]

Woah, definitely NOT normal. The belt should be very firm and centered on the wheels. Good thing you decided to open it up, because that could have been catastrophic. I also would not be surprised if your timing was off by a fair bit. So I would guess that yes, your performance was affected.

 

[torqueluvr]

Thanks everyone. I got the pump out in the mail today for a reseal. When I get the pump back I'm assuming I can install it and then take it to a diesel shop for a timing job? Or can I do that myself? I have the FSM, but haven't looked into that part yet.

 

[tweeek]

Rotate your crankshaft bolt slightly forward, I bet it tightens up. I had the same question when I had mine off a couple years ago. If the crank is turned backwards even a tiny bit it introduces alot of slack into the belt, just the way the spring tensioner works.

You can easily check your timing marks on the gears to tell if it's skipped, but I doubt it.

Either way, it's never going to be easier to replace then right now. It's not a big job.

Pump timing can be done by yourself, you need a dial gauge and adapter that can be had off the interwebs. Google bosch ve timing adapter

 

[dan1554]

You can do the timing yourself with a dial gauge. This is what I used, no longer available but I’m sure there are more out there. It was cheap. I had to cut one of the probe extensions a bit to get it to work.

Metric Dial Indicator and Holder Tools for Bosch diesel injection pump Timing https://www.amazon.com/dp/B01N5TQ4YE/ref=cm_sw_r_sms_c_api_BIXSAb24JD89J

 

[mudgudgeon]

Rotate your crankshaft bolt slightly forward, I bet it tightens up. I had the same question when I had mine off a couple years ago. If the crank is turned backwards even a tiny bit it introduces alot of slack into the belt, just the way the spring tensioner works.

This is not something I've noticed. Once tensioner is in place, belt stays taught from my observation.

 

[mudgudgeon]

When I get the pump back I'm assuming I can install it and then take it to a diesel shop for a timing job?

Yes you can self install, but do some reading first. It is possible to cause a side load on the pump shaft seal causing premature failure.
Follow the FSM.

you should be able to match up the alignment marks on the pump housing and timing cover to get timing far enough into the ball park to be able to start it, but it's rough, so timing needs to be done with a dial gauge.

 

[tweeek]

View attachment 1659737

This is not something I've noticed. Once tensioner is in place, belt stays taught from my observation.

I challenge you to rotate your crank backwards and see what happens. I went through a similar issue when I swapped my hdt a couple years ago.

I posted about it here;
1HDT Timing belt tensioner


A couple responses I received confirmed what I was seeing as the tensioner pivots and slides. The top side of the belt can be loose while the bottom side is tight until engine is rotated. This was the case with mine as well.

 

[618Henrik]

Rotate your crankshaft bolt slightly forward, I bet it tightens up. I had the same question when I had mine off a couple years ago. If the crank is turned backwards even a tiny bit it introduces alot of slack into the belt, just the way the spring tensioner works.

You can easily check your timing marks on the gears to tell if it's skipped, but I doubt it.

Either way, it's never going to be easier to replace then right now. It's not a big job.

Pump timing can be done by yourself, you need a dial gauge and adapter that can be had off the interwebs. Google bosch ve timing adapter

I replaced mine last weekend, and it was exactly the same, loose until I turns the engine. Maybe depends on how the cams sits when the engine stops?

 

[mudgudgeon]

I challenge you to rotate your crank backwards and see what happens

Challenge accepted! I'll get right on it . . . ..


in 98k km when it's due for another belt

I was taught its best practice not to rotate an engine backwards. If you are lining up timing marks etc and go too far, keep rotating it until marks come back around. Granted, it's a bear turning over a big I6 with 22:1 compression, but I try to stick to that.
Maybe this is a good example of why.

Obviously, an engine isn't going to rotate backwards in use, unless you've seriously fxxxed something up

I'd be interested to know if the OP had rotated the crank backwards

 

[torqueluvr]

I don’t think I rotated it backwards. The notch was at the TDC point when I took the belt off. I rotated it to BDC which is 12 oclock, from 9 oclock. Clockwise. I think that’s right?

Heard back from Jon Fox aka Yotahead on my pump. All is good it just needed a reseal. Should be back here by Monday and then i’ll install Monday night along with the timing belt kit and we’re back in business.

 

[dan1554]

The FSM tells you to rotate the engine backward when checking timing. No slop when I did that. Granted the belt and tensioning spring are only ~10k km old.