WTAF is causing my 1HD to throw belts?

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I have a 96 hdj80r manual. Had it for about 100k, long engine rebuild about 40k ago. Alternator replaced about 15k ago, and recently I've started towing a heavy load, so have been looking for more output, and largely changed the way I drive, mostly keeping the motor in the 2200 to 2800 range. I've also fitted a better turbo, had the injectors replaced and fitted a large fmic.

It started throwing belts about 1000 ago, since then I've had multiple failures. Sometimes the ac belt would give up first, other times one of the fan belts. I changed the ac idler first, the compressor pulley feels fine. No good. I've just replaced the harmonic balancer with a fourth new set of belts, and within an hour it inverted the rear fan belt. Didn't come off but obviously would have done, and the belt is u/s.

I did notice the alternator pulley is hot. Too hot to touch. It feels fine, but I'm beginning to wonder if an overloaded alternator could cause this issue? I have 3x batteries in parallel in the vehicle (been fine for a decade that way) and now and Andersen 12v connector out to the trailer, which might want 40a.

Otherwise, the fan pulleys are mounted on the water pump, right? Should this be my next focus area?
Very much appreciate any sage counsel here.

Cheers,
Alex
 
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Well I don't think my reply would qualify as "sage advice", but I've got a few questions. Are the belts snapping? Do you hear any screeching?

For a belt to flip or come off without breaking, it suggests you're losing tension. Are you sure the belts are tensioned correctly?

My first guess would have been the rubber in the harmonic balancer separating, but you said that's been replaced, so I'm not sure exactly. Is your alternator physically moving? That'd be my next guess. Perhaps check the tensioning bolt and nut around the top alternator mount carefully?
 

Irish Reiver

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You mention the trailer is pulling 40 Amps, does it only throw the belts when the trailer is hooked up? It sure sounds like you have an alternator issue - maybe not capable of delivering the amperage you need or the belts are not tight enough causing slippage, slap and ultimately throwing them.
 
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Well I don't think my reply would qualify as "sage advice", but I've got a few questions. Are the belts snapping? Do you hear any screeching?

For a belt to flip or come off without breaking, it suggests you're losing tension. Are you sure the belts are tensioned correctly?

My first guess would have been the rubber in the harmonic balancer separating, but you said that's been replaced, so I'm not sure exactly. Is your alternator physically moving? That'd be my next guess. Perhaps check the tensioning bolt and nut around the top alternator mount carefully?
Thanks. The belts will snap if I don't get to them quickly when they come off, but that's down to them becoming entangled. No squealing.
I'm pretty sure the tension is good, but I started to second guess myself there so got a mate to bring his calibrated thumb over to check me- we're pretty sure the tension is good.
Yes, brand new oem hb went on yesterday. I don't detect any movement in the alt. The adjuster seems fine, even if it's a bastard to reach now there's intercooler pipes in the way!
Eyeballing the belts I saw that the rear alternator belt was exhibiting some twist off the bottom of the crank pulley in the run toward the alternator with revs tending north of 2400ish, and that this condition subsided past 3k. I have to question whether in fact this might have been a sub standard belt. I'll try a pair of a different brand.
I suppose I didn't have much choice but to remove the alt and mounting brackets altogether for a detailed inspection. And today it will be 41celcius.
 
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You mention the trailer is pulling 40 Amps, does it only throw the belts when the trailer is hooked up? It sure sounds like you have an alternator issue - maybe not capable of delivering the amperage you need or the belts are not tight enough causing slippage, slap and ultimately throwing them.
Trailer has an absorption fridge, I did throw a belt off without the trailer attached recently, but it was a belt that had previously thrown re installed to limp home. I am also pondering whether the additional trailer load, which prevents engine speed from increasing as rapidly, may keep the motor in the belts throwing range for longer and make it seem like there's a relationship that doesn't really exist.
 
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Another new matched pair of belts today, different brand, just in case the ones fitted after the HB install were s***. I set them up with the lettering aligned and a gentle tension, and ran the motor for a couple of minutes, they immediately lost alignment with one another. I back the tensioner off, set them in alignment again, and applied the kind of tension I would ordinarily want, which is a deflection of about 10mm in the middle of the run between crank and alt, and ran it again. Once again the belts went out of sync in short order.

Eyeballing the belts with motor running, it seems like the rear one is looser than the front, and that's got me puzzled. I haven't yet removed the alt brackets for inspection.
 

ppc

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Having the belts go out out of sync is normal.

I think you need to verify that all the pulleys are operating in the same plane with a straight edge and have no play.
 

mudgudgeon

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Have you checked bearings in the alternator?

I wouldn't stress about lettering on belts shifting out of alignment if it took a while, but if it's happening straight away suggests something is not square to the line of the belts.

What brand belts? OEM or aftermarket?
I try to keep to OEM.

Are any of the pulleys badly worn? V groove too wide?
If the groove in the pulleys are worn out and too wide, it can cause issues as the belt effectively only has tension on the outer face of the belt.
The belt should get friction halfway down the sides of the V, not on the canvas outer surface.
 

mudgudgeon

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Maybe cut a piece of one of the rejected belts and check bent engagement in the groove.

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If one groove is worn deeper than the other, the belts are looped around a different overall circumference. Tension will be different, and number of rotations will be different
 

Dave 2000

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First thing is to look at the hot alternator that should never really be too hot unless it is maxing out and then would only get really hot when you switch off as does your engine. Next look at the rearmost mount that holds the alternator, the bolt is often found loose and it causes the hole in the bracket to elongate, seen this a couple of times on the HD. I have never seen a pair of matched and aligned belts run in sync ever, slight differences in pulley wear will throw them out of sync very quickly, I would also check out the batteries, if one of more has a shorted plate inside it will for want of a better description 'refuse' the charge causing the alternator to ramp up it's output.

With the belt off also spin the water pump and give it a spin and put sideways tension on it and feel for it jamming as the bearings wear the impeller can jam inside the housing causing belts to be thrown or run off the pulleys.

Sounds a lot but I having 'lived' under the bonnet of cars and truck for around 50 years, I have pretty much seen it all.

Regards

Dave
 
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Thanks very much everyone. I'm going to pull the alternator and its bracket tomorrow. I do have an old dead on kicking around, which while it didn't charge, it didn't throw belts, so will chuck that in and see if the belts behave the same. The concept of the pulley becoming unevenly worn on the new alt is something I hadn't considered and would support the two belts showing different levels of tension. Will also take a closer look at the bracket. I think I'll try to rule out the alt before moving on to the WP, if only for my own sanity, I need to know what ultimately caused this !
Cheers.
 

Dave 2000

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Thanks very much everyone. I'm going to pull the alternator and its bracket tomorrow. I do have an old dead on kicking around, which while it didn't charge, it didn't throw belts, so will chuck that in and see if the belts behave the same. The concept of the pulley becoming unevenly worn on the new alt is something I hadn't considered and would support the two belts showing different levels of tension. Will also take a closer look at the bracket. I think I'll try to rule out the alt before moving on to the WP, if only for my own sanity, I need to know what ultimately caused this !
Cheers.
Don't forget the water pump, but the alternator bracket would be a regular given that you changed it and the old alternator did not throw belts, it is possible the bolt worked loose allowing the alternator to 'turn in' at the front as the belt tension is adjusted.

Regards

Dave
 
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Don't forget the water pump, but the alternator bracket would be a regular given that you changed it and the old alternator did not throw belts, it is possible the bolt worked loose allowing the alternator to 'turn in' at the front as the belt tension is adjusted.

Regards

Dave
Thanks Dave. This is the thing though, wouldn't we expect to see a looser front belt in that scenario? I wonder if I can get the bastard off without having to drain the coolant? I guess I'll find out :)
 

Dave 2000

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Thanks Dave. This is the thing though, wouldn't we expect to see a looser front belt in that scenario? I wonder if I can get the bastard off without having to drain the coolant? I guess I'll find out :)
No not at all, the amount of 'out of alignment' needed to make a belt start to come off the pulleys is very small. If you think about it the belts are supposed to sit in the 'V' pull the pulley around with it. If the belt is trying to climb or ride up against the side of the pulley it will start to heat up, as it does it will become for want of a better word 'sticky' and making the climb up the pulley easier.

Re the water pump, I am not suggesting taking the water pump off to test it, I am saying with the belts removed grasp the water pump and pull or push the pulley to one side hard while turning it, if the pump bearing is wearing then the load of the belt will tip the pump impeller (clearance is only a few thou) and cause it to jam against the inner casing. Some of the impellers are plastic so unlikely in that case but if you have the steel impeller? Also don't be surprised if the AC belt which IIRC is separate is coming off and committing 'Harry Cary' and throwing itself into the path of the alternator/pump pulleys/belts.

Regards

Dave
 
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OK, some further dismantly and inspection. Pics are a bit big, sorry abt that. Alt pulley looks and feels fine, no evidence of belts bottoming or causing irregular wear patterns oddly.

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Ahh- alt tensioner bracket displays a crack right through it - mind you it ought to be in compression didn't it? Will weld this up.


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Top WP bolt hole loses coolant! :( This can't be right?


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Cheers
 
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Mate of mine has fixed up the bracket for me, fantastic work. Ground a few mm out to ditch the oxidised ends of the crack and welded in a new section. He's even annealed the repair.
I've elected to change the water pump anyway, I'd forgotten about the cam pulley. I'm thinking of a lash up top with a couple of books to engage the holes in the cam pulley rather than pull the valve cover too. Any other neat tricks? Can't get at it with impact driver.

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Dave 2000

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Did you pull the alternator off and check the bracket, pretty much impossible to check without removing.

Regards

Dave
 
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Did you pull the alternator off and check the bracket, pretty much impossible to check without removing.

Regards

Dave
You mean the bottom one? Not yet, won't come off without removing the 'stat housing. Will come off tomorrow. You don't like the idea of the tensioner bracket being cracked as the cause, I can tell... How about the half full of mud wp pulley?
 

Dave 2000

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You mean the bottom one? Not yet, won't come off without removing the 'stat housing. Will come off tomorrow. You don't like the idea of the tensioner bracket being cracked as the cause, I can tell... How about the half full of mud wp pulley?
You right, the adjuster would be trapped between the alternator and the securing bolt, the adjuster might have allowed the alternator to 'turn in' a little but only if the bottom bracket is worn. If the mud was trapped between the pump and the pulley when the pulley was fitted then the pulley would have come loose as the mud dried out.

You have not said if there is any play or if you like side to side movement of the pulley, it will be interesting if when you take the pump off you can see if the impeller had touched the area where it runs close to the pump body, also water dripping onto the pulley would allow the belts to slip and burn through eventually.

IIRC you say you replaced the crank pulley? Did it seat correctly, does the outer and inner piece look secure? I run a line of white paint over mine, this tells you if and when they are slipping out of alignment.

Regards

Dave
 

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