Hi guys,
Recently changed the alternator belt, because the old one was squeeking/slipping on startups.

Changed to new one , but it took a week or two till new one began to slip as well.

The belt is very well tightened, and there is no more room to tighten, but still i have slipping on mostly cold startups.

Used some special spray for anti belt slipping, but that makes it for just a couple days.

Is there something with alternator pulley wrong, or is it the belt issue?
Has anybody had similar issues?

 

May have had the wrong belt as you received the car and you duplicated the same size as you replaced it . The official Jaguar part number is below : Item # 1

https://www.jaguarclassicparts.com/u...e-supercharged

I have the stamped Jaguar 11306 in my hands and is a 5 rib ( or points ) x 38.75 inches ( 984 mm ) long on the outside perimeter

With also the stamped DAYCO 20 - 4553 on the same belt

 

I replaced the oem belt. It was slipping but was in very good shape.
Put new one not oem type , but visualy looked same grove shape and size.
Since it started to slip very early i assume its not belt related issue but puley issue.
I have read somewheare that pulley grooves need to be sanded so the belt fits more tight. I believe on xk forums somewhere.

 

You will likely need to replace or repair the crank damper.

bob

 

Found these links : if it is so

Saw on a post somewhere wedging the wrench on the side sheet metal and bumping the starter breaks the nut loose . Test for dampener pulley slippage as well as water pump leakage on belt in the first link by Bob Gauff . I put a 34 mm socket on mine and it doesn't move around from point to point too much , safer bet that it's a 33 mm without putting a micrometer on it .

https://www.jaguarforums.com/forum/x...alancer-84531/

https://www.jaguarforums.com/forum/x...nating-102422/

https://www.jaguarforums.com/forum/x...lancer-101674/

https://www.jaguarforums.com/forum/x...emoval-191240/

 

I am reviving this thread originally posted by RB_jaguar, as I too have an issue with the OEM specs for the alternator belt. Bought a set of three belts but mechanic found the new alternator belt as loose as the used one. The stamp on the original and new belt are both "5PK975", but they are made by different manufacturers. "5PK975" is interpreted as "5" meaning 5-rib, 975 is 975mm in length. Mechanic said owing to the presence of the supercharger, space was very tight in the lower half of the engine so he wanted to make sure that belt movement is free from other parts in the engine bay. We then bought and tried to fit a shorter one "5PK970", but mechanic found it only slightly tighter and worried that it might become loose pretty soon. We tried but failed to find "5PK965"; some shops said it was all sold out, some said there is no such size. Eventually found a "5PK960" which is too tight (15mm shorted than specs) but the mechanic managed to put it in place by adjusting various tensioners/pulleys. Belt has been working well and quiet. So we wonder if the original spec of 975mm might be too long or it is just because of production variance by different belt suppliers.

 

I just bought the Gates or Dayco (I forget which) that is the OEM cross reference and it went on fine and I was able to tighten it to spec without issue and with room to spare to keep tightening.

So maybe manufacturer variance or the wrong belt in the package?

.

 

My 975 is part of a belt set from British Parts. Maybe it shouldn't be 975 in the first place. The 970 and 960 were sourced from local car parts shops. Mechanic said his experience of belt fitment is that other code numbers on the belts, which look like batch number on canned food, also mean something, so cases where a car needs two belts of the same specs, he would ask the shop selling him the belts to make sure that both belts are from the same production batch, as there may be some variance among different manufacturers or even from the same manufacturer due to production date, material used, etc.

 

Would be worth checking that the water pump rotates freely while the belt is off. If a water pump bearing is about to seize you might get belt slippage. How did you set belt tension?

 

The mechanic has checked the water pump as well as the alternator and all pulleys; nothing loose. 970 would fit but he figured would become loose again soon so ....... in putting in 960 as 965 was not available he made other adjustment to enable a shorter belt to work. He is probably the best mechanic in town and knows what he is doing. However, the belts turn fine for a few days and start to squeak a little now. Will see if I can find a 965 belt.

 

In my case i just tightened it little bit more. Probably since it was new it got little bit longer.
Couple weeks was just fine, no squeeking for now.

It looked as its a harmonic balancer issue, but i did the marks with paint and its ok for now.

 

Maybe the pulley surface has been eroded and does not bite enough onto the belt. Read about vulcanizing or re-vulcanizing the pulleys to make the belt fit and run better in the case of conveying belts. Not sure if this process is suitable for alternator belt. Maybe replacing the pulley would be a more fitting solution.