Fan belts.

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chrisfell
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#1 Fan belts.

Post by chrisfell » Tue Jul 31, 2018 3:43 pm

Has anyone else had to replace more than one fan belt recently? I’ve just lost my third in about 5,000 miles. The first just stretched, was about 30,000 mile old, so I’ll forgive it. The next two shredded themselves, individual wire ropes breaking away from the carcass. I’ve already checked the pulleys for damage and found none so I’m suspecting the belts themselves. If no one else has had a belt fail prematurely it is more likely to be something I’ve not spotted on the car yet.
Chris '67 S1 2+2

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Heuer
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#2 Re: Fan belts.

Post by Heuer » Tue Jul 31, 2018 3:49 pm

Other than faulty manufacture the two most common causes of premature belt failure are a) oil contaminating the belt and b) pulley's slightly out of alignment. Both manifest themselves by shedding ropes from the carcass and you can usually hear them slapping about.
David Jones
S1 OTS OSB; S1 FHC ODB
1997 Porsche 911 Guards Red

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cactusman
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#3 Re: Fan belts.

Post by cactusman » Tue Jul 31, 2018 4:26 pm

Adding to David's suggestions vastly over tensioned or under tensioned may also cause premature failure. Over tension probably won't have symptoms until the belt fails. Under tensioned and it will squeal especially just after being started when the alternator is 're charging the battery or when the head lights are switched on. Very very rough rule of thumb...correct tension will allow about a cm or so of belt deflection either way on the run from the alternator to the water pump pulleys when poked with a finger. My ancient old one was changed five years back. Done about 7000 miles and looks mint.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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#4 Re: Fan belts.

Post by chrisfell » Wed Aug 01, 2018 7:56 pm

As far as I can see the pulleys are all in line. And as far as I can see, there is no damage to any of the pulleys. So the initial verdict could be over tightening. Of which I am guilty.

However, there have been two developments.
1. I now know with some precision what it feels like to have the middle finger of my left hand grabbed by a passing fan belt and run over the alternator pulley. It mangles said finger.
2. I now have a selection of fan belts from our favourite major supplier, two supplied with incredible speed barely 18 hours after they were ordered yesterday.

I have two distinct types of belt. One has a canvassed outer surface and has a smaller cross sections than the other, which has a smooth outer surface. The larger of the two is the one that shredded itself.
Chris '67 S1 2+2

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abowie
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#5 Re: Fan belts.

Post by abowie » Wed Aug 01, 2018 10:06 pm

chrisfell wrote:
Tue Jul 31, 2018 3:43 pm
. The next two shredded themselves, individual wire ropes breaking away from the carcass.
We've had a number do exactly this on customer's cars over the last year or two. Our surmise was a bad batch. These came from Manners, but I assume they are all made in the same place.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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#6 Re: Fan belts.

Post by chrisfell » Thu Aug 02, 2018 9:39 am

Getting somewhere now, I have some data.

The belt that shredded itself has an overall height in cross section of 0.5”. The older belt which didn’t shred but just stretched, 0.375”. The pulleys have a groove depth (max, from outer edge) of 0.3”.

This means that the belt that failed was proud of the pulley by 0.125”. This might be the determining factor.

Image

The oversized belt was marked SBS1100 C19525. The smaller (in cross section) belt was marked C24291C. C19525 is listed as the belt for 3.4 and 3.8 Mk 2s, Mk 10s and S-Types. I suggest these should not be used on E-Types even though, being double V and 1100mm long, they will fit. C24291C is the correct part number for E-Types.

Image

If any other listers have similar failures and can measure the belts and check the markings we may be on the way to solving the problem, even though I cannot conclusively say what the actual cause was.
Chris '67 S1 2+2

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ralphr1780
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#7 Re: Fan belts.

Post by ralphr1780 » Thu Aug 02, 2018 10:47 am

Chris,
C19524 is 1010mm
C19525 is 1050mm
C24291 is 1100mm

On my S1 3.8 the C19524 has been fitted without difficulty, almost 300km done now with no change in aspect or integrity.
Ralph
'69 OTS + '62 OTS - Belgium

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#8 Re: Fan belts.

Post by cactusman » Thu Aug 02, 2018 12:49 pm

My belt is marked SBS1010 C19524 and is a correct fit for 3.8 e types without a belt tensioner. Been there five years. Came from SNGB I think. The Jaguar parts book states the belt is "C19524 for engines R5250 to R9999 RA1001 and subs"

I suspect the longer belt C19525 is for cars fitted with the spring loaded belt tensioner as when I replaced mine that was the part I initially ordered. It was too long.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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#9 Re: Fan belts.

Post by Heuer » Thu Aug 02, 2018 1:05 pm

This is everything I have been able to find out about fan belts for the Factory Fit thread. May provide some context:

C15840
The first 500 cars up to #860004, 885020, 850091 & 875385 had the XK 'S' engine, which was basically the same one fitted to the XK150 S, hence the 'pumpkin' head colour. These used a 'V' belt of 1/2" width, 40° angle, 39 3/8" outside circumference, 36 3/4" inside circumference and 7/16" thick. Jaguar part C15840 e.g. Mintex reference WKT399:
Image
Image

C15840 'N' suffix
After the first 500 and up to engine R5249 (~January 1963) a 'notched' drive belt C15840 was used ('N' suffix in after market catalogues) of slightly different dimensions (wider at 1/2"). In October 1961, from engine no R1845, a fan belt tensioner was fitted but required no change to the fan belt.
Image

C19524
From R5250, RA1001 and subsequent a Duplex (twin-vee) drive belt C19524 was used and required modified pulleys. It was at this point ~ January 1963 that Jaguar began supplying a spare belt because its unusual design meant finding a replacement at Motor Factors was difficult. Although the Duplex belt is slightly shorter it could still be used to replace the earlier notched belt, but not vice versa obviously. The belt as supplied was coiled with an identifying card label
Image
Image
Image
Image
Image
Image
Last photo courtesy of Roger Payne.

Despite searching many period catalogue's we cannot find an after-market 'Duplex' belt nor indeed much trace of the earlier notched belt. Here is the only example found so far, the John Bull 122N:
Image
Image

At the moment all we can say is that this after market John Bull belt fits and is notched. We have no evidence to suggest they were the OEM, as yet.

C24291
For the 4.2 cars the belt was changed to C24291 to accommodate the alternator pulley with its different diameter to the dynamo and had a 40.5" outside circumference. If we are going to compare belts I suggest we use the measurement table as in the photo above: Top width, Angle, Outer Circ, Inner Circ and Width in imperial. The width is probably the most important as if it is too wide it will shred.

On my 3.8 the notched C15840 belt is 1/2" wide, on the 4.2 with the C24291 belt it is 7/16" wide.

Note: Dunlop bought The John Bull Rubber Co. in 1959 but continued with the brand name until about 1963
David Jones
S1 OTS OSB; S1 FHC ODB
1997 Porsche 911 Guards Red

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