200tdi not holding belt tension

dag019 · May 30, 2023

I have a discovery 200tdi fitted, it is the standard discovery 200tdi setup where the fan belt runs crank, pas, water pump and the second belt runs pas pump to alternator.

The fan belt and alternator belt do not hold tension. I had fitted new belts as part of the rebuild (burnt out rebuild), I know new belts will stretch but I tensioned them when I fitted them, they have run a little in the barn and to move around the farm yard and were re-tensioned before the MOT, they were then re-tensioned again on retuning home from the MOT (about 40miles). After a 300mile drive to Scotland they were very very slack and had been slipping towards the end of the journey. I re-tensioned the belts, fitted some new spring washers behind the bolts to try and prevent the pas pump moving and headed home. 250 miles into the journey home the belt started slipping again and it threw the fan belt.

Now home and I have dug out the spare belt I have on the shelf and will fit that for the time being. Looking at the pulleys they are rust pitted so I am going the change them out and see if that improves things. If someone could confirm the part numbers below for the pulleys before I order them that would be great:

Water pump pulley: ETC5499
PAS pulley: ETC7528
Alternator pulley: RTC5686 (13mm belt) / RTC5847 (10mm belt) - believe I need the 10mm one but could I fit the wider one and use a larger belt?
Crank Pulley: ERR3093 (three groove) / ERR2352 (2 groove) - I believe I need the two groove pulley as that is what is fitted to discovery and RRC?

This still leaves me with the issue of not holding the tension however. I have had this problem previously with the alternator and just need to order some high tensile nuts and bolts along with some star or wedge locking washers. It is the PAS pump I have not had fail to hold tension before. I will try similar with some high tensile bolts and some star or wedge locking washers but it is only into an ali bracket so cannot put too much toque through it before the threads will fail. This may also already be the issue as it did not feel as good as it could have done when tensioning. If the locking washers do not help with the pas pump I will look to either replace or helicoil the bracket, does anyone know the part number for the bracket and if you can still get them?

Does anyone else have any other suggestions of things to try and remedy this so I can get back on the road properly after the rebuild?

meego · May 30, 2023

dag019 said:
I have a discovery 200tdi fitted, it is the standard discovery 200tdi setup where the fan belt runs crank, pas, water pump and the second belt runs pas pump to alternator.

The fan belt and alternator belt do not hold tension. I had fitted new belts as part of the rebuild (burnt out rebuild), I know new belts will stretch but I tensioned them when I fitted them, they have run a little in the barn and to move around the farm yard and were re-tensioned before the MOT, they were then re-tensioned again on retuning home from the MOT (about 40miles). After a 300mile drive to Scotland they were very very slack and had been slipping towards the end of the journey. I re-tensioned the belts, fitted some new spring washers behind the bolts to try and prevent the pas pump moving and headed home. 250 miles into the journey home the belt started slipping again and it threw the fan belt.

Now home and I have dug out the spare belt I have on the shelf and will fit that for the time being. Looking at the pulleys they are rust pitted so I am going the change them out and see if that improves things. If someone could confirm the part numbers below for the pulleys before I order them that would be great:

Water pump pulley: ETC5499
PAS pulley: ETC7528
Alternator pulley: RTC5686 (13mm belt) / RTC5847 (10mm belt) - believe I need the 10mm one but could I fit the wider one and use a larger belt?
Crank Pulley: ERR3093 (three groove) / ERR2352 (2 groove) - I believe I need the two groove pulley as that is what is fitted to discovery and RRC?

This still leaves me with the issue of not holding the tension however. I have had this problem previously with the alternator and just need to order some high tensile nuts and bolts along with some star or wedge locking washers. It is the PAS pump I have not had fail to hold tension before. I will try similar with some high tensile bolts and some star or wedge locking washers but it is only into an ali bracket so cannot put too much toque through it before the threads will fail. This may also already be the issue as it did not feel as good as it could have done when tensioning. If the locking washers do not help with the pas pump I will look to either replace or helicoil the bracket, does anyone know the part number for the bracket and if you can still get them?

Does anyone else have any other suggestions of things to try and remedy this so I can get back on the road properly after the rebuild?

I also have a D1 200tdi in my 90, and when I last changed the belts, I kept the sleeves for future reference. I hope this helps.

dag019 · May 30, 2023

meego said:
I also have a D1 200tdi in my 90, and when I last changed the belts, I kept the sleeves for future reference. I hope this helps.

Many thanks, I already have a set of belts on the shelf that are dayco. But the part number of the gates belts confirms the measurements I had taken.
Fan: length 1030mm, width 13mm
Alternator: length 613mm, width 10mm

I just need to work out if the PAS pulley will allow for a wider alternator belt to be fitted or it the grove is just too narrow.

meego · May 30, 2023

dag019 said:
Many thanks, I already have a set of belts on the shelf that are dayco. But the part number of the gates belts confirms the measurements I had taken.
Fan: length 1030mm, width 13mm
Alternator: length 613mm, width 10mm

I just need to work out if the PAS pulley will allow for a wider alternator belt to be fitted or it the grove is just too narrow.

No problem. The fact that it’s losing tension would suggest the bolts loosened, but you seem to have covered that. Can you try bigger washers on the clamp bolts to create more surface tension ??

v8250 · May 30, 2023

@dag019 , I too have had this happen in the past, albeit on an older classic car. I change the nuts & bolts replacing with [ as @meego ] with new bolt, larger flat washer, thread side larger flat washer, a spring washer and finally a full sized nut. Installed the same on the Ninety 200tdi for both alternator and PAS pump. No problems.

freelance · May 30, 2023

Are you sure it’s not the pitted pulleys wearing the belt prematurely?

lynall · May 30, 2023

freelance said:
Are you sure it’s not the pitted pulleys wearing the belt prematurely?

Just this weekend I had to go and look at a boat where the guy said he had problem with severe alt belt wear, and had spent hours trying to work out why, so I forced my slender gut into the void and 10 seconds later said you have fitted the belt onto the crank pulley and it does not run off the crank pulley! the crank pulley which had never seen a belt for 30 years and was badly pitted, this was what was chewing up the belt.

Years ago I ran a disco 200 as my daily, and it was a non stop affair keeping the alt belt tensioned.
Defender 200 pas belt is much the same and that is the 1/2 belt, so I do not think a wider belt will sort your issue.

Basically single V belts are shti!
Twin V belts are actually quite good.

dag019 · May 30, 2023

freelance said:
Are you sure it’s not the pitted pulleys wearing the belt prematurely?

No I am not, that is the first thing I am going to do is replace the pulleys, but at the same time I am going to add locking washers to the adjusting bolts as they do not have any currently. Doe a belt become slack form excessive rust wear or just chaff?

lynall said:
Years ago I ran a disco 200 as my daily, and it was a non stop affair keeping the alt belt tensioned.
Defender 200 pas belt is much the same and that is the 1/2 belt, so I do not think a wider belt will sort your issue.

The previous disco 200tdi I had fitted did not have this issue, needed the alternator belt tensioning about every 12 months which I put down as as service wear with the high mileage I do, and never touched the fan belt. I know you can get a 13mm (1/2") alternator pully but I do not know if the pas pump dual pulley would take the wider belt. If it does I will upgrade the alternator to the wider pulley to help that too.

lynall · May 30, 2023

dag019 said:
No I am not, that is the first thing I am going to do is replace the pulleys, but at the same time I am going to add locking washers to the adjusting bolts as they do not have any currently. Doe a belt become slack form excessive rust wear or just chaff?

The previous disco 200tdi I had fitted did not have this issue, needed the alternator belt tensioning about every 12 months which I put down as as service wear with the high mileage I do, and never touched the fan belt. I know you can get a 13mm (1/2") alternator pully but I do not know if the pas pump dual pulley would take the wider belt. If it does I will upgrade the alternator to the wider pulley to help that too.

Mark the bolts and alt postion to see if it is actually moving.
You could get the alt pulleys skimmed on a lathe to accept a wider belt this would also have the added bonus of cleaning them up at the same time.
You can get different width belts, so for example you could get the pulleys skimmed on a lathe and fit an 11mm wide belt if there is not enough meat to go to the 12.5mm wide belt.

Local bearing factor will get what you want, or try simplybearings online.

freelance · May 30, 2023

dag019 said:
No I am not, that is the first thing I am going to do is replace the pulleys, but at the same time I am going to add locking washers to the adjusting bolts as they do not have any currently. Doe a belt become slack form excessive rust wear or just chaff?

The previous disco 200tdi I had fitted did not have this issue, needed the alternator belt tensioning about every 12 months which I put down as as service wear with the high mileage I do, and never touched the fan belt. I know you can get a 13mm (1/2") alternator pully but I do not know if the pas pump dual pulley would take the wider belt. If it does I will upgrade the alternator to the wider pulley to help that too.

Yes as the belt gets thinner it is effectively looser around the pulleys

dag019 · May 30, 2023

freelance said:
Are you sure it’s not the pitted pulleys wearing the belt prematurely?

@freelance gets a cookie!
Having fitted new belts, dayco alternator and gates fan belt, the new belts are tight with no adjustment. I deliberately wrapped the new belt around rather than slackening off and they were nice and tight once fitted.
I also wire wheeled the grooves on all pulleys so they are nice and clean.

meego · May 30, 2023

dag019 said:
@freelance gets a cookie!
Having fitted new belts, dayco alternator and gates fan belt, the new belts are tight with no adjustment. I deliberately wrapped the new belt around rather than slackening off and they were nice and tight once fitted.
I also wire wheeled the grooves on all pulleys so they are nice and clean.

View attachment 289444 View attachment 289443

I think I would have a bigger washer on the bottom bolt in the adjustment slot you can just see under the pulley.

tottot · May 30, 2023

On the whole v belts work well an last well, however they do not like rusty pully's, running out of alignment, wrong belt section, [angle of the v and pully groove] being aloud to run loose or being overloaded by an item that has seizing bearings.

lynall · May 31, 2023

tottot said:
On the whole v belts work well an last well, however they do not like rusty pully's, running out of alignment, wrong belt section, [angle of the v and pully groove] being aloud to run loose or being overloaded by an item that has seizing bearings.

Flat belts are the kiddies, we have several trucks with a million kms still on the original belt.

dag019 · May 31, 2023

meego said:
I think I would have a bigger washer on the bottom bolt in the adjustment slot you can just see under the pulley.

It is a flanged bolt with a spring washer, if I had needed to adjust the tension again I would have fitted a large washer to all of them as well, but the tension was fine with the new belt. If I need to adjust once the belt has bedded in I will fit washers then.

200tdi not holding belt tension

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