Alternator/water pump belt keep burning off

[MacinTek]

Yes, I've tried spinning both water pump (>10 years old) and alternator (< 2years old). Both spin as they should. Yet, I install a new belt and tension it so it doesn't slip or strain, and, within a quarter mile, I see smoke rising from the engine bay and the alternator light comes on... sure enough, belt is gone.

What else should I be looking for?

[SamHill]

Yes, I've tried spinning both water pump (>10 years old) and alternator (< 2years old). Both spin as they should. Yet, I install a new belt and tension it so it doesn't slip or strain, and, within a quarter mile, I see smoke rising from the engine bay and the alternator light comes on... sure enough, belt is gone.

What else should I be looking for?

Reinstall belt. Tension as needed. Take a piece of string, holding one end, and let it fall toward the ground. Move the string toward the middle of the belt. Is the top of the belt aligned with the bottom?

[DMC-81]

Some things to check:

1) The alignment of the water pump/alternator/crank pulley to ensure they are all flush and not cocked out of alignment ( especially the alternator)

2) Is the water pump stock? Sometimes a non-stock water pump pulley makes the alignment off.

3) Is the alternator /pulley / bracket stock ?

4) Is there anything close to or actually interfering with the belt ( e.g. A different bracket or shield etc)?

5) Re-check the tension. (As mentioned above^). It doesn't need as much as one might think.

[Jonathan]

What make and model of belt are you using and where did you get it (them)?

[dmcnc]

If you could also share pictures of your set-up that would be helpful.

[David T]

Inspect the weep hole on the bottom of the neck of the water pump. If you see any staining replace the water pump. Make sure the alternator is lined up with the other pulleys. Don't overtighten the belt.

[Andrew]

Make sure the large alternator bolt is not over-tightened. I had a similar problem and the upper bolt turned out to be the culpret. I backed off the bolt slightly and the problem was resolved.

[DMCMW Dave]

Some things to check:

1) The alignment of the water pump/alternator/crank pulley to ensure they are all flush and not cocked out of alignment ( especially the alternator)


This one. You probably have the spacers screwed up on the alternator mount. What alternator is it? Stand to the side of the car and sight along the belt and the two pulleys. Also look straight down - a water pump with an improperly installed pulley will do this. Make sure it matches up with the crank pulley.

Too loose is worse that too tight BTW. If too loose it will slip.

[Blackie]

I had a similar issue many years ago. The water pump pulley is the press on type and had started to back off the shaft. The shaft has an internal thread, i used a long socket and a bolt to press it back on, then had a spacer machined up to keep on there permanently to keep it from backing off again.

[TGGreene]

Yes, I've tried spinning both water pump (>10 years old) and alternator (< 2years old). Both spin as they should. Yet, I install a new belt and tension it so it doesn't slip or strain, and, within a quarter mile, I see smoke rising from the engine bay and the alternator light comes on... sure enough, belt is gone.

What else should I be looking for?

The stock muffler is about an inch from the lower pulley and belt. That muffler gets seriously hot seriously fast. Is the factory heat shield betweent the muffler and the pully/belt still there? Mine had been broken. I made a new one out of a sheet of metal reinforced exhaust gasket material that I bought from NAPA. Cheap, looks pretty much factory, and and works perfectly.

[DMCMW Dave]

I had a similar issue many years ago. The water pump pulley is the press on type and had started to back off the shaft. The shaft has an internal thread, i used a long socket and a bolt to press it back on, then had a spacer machined up to keep on there permanently to keep it from backing off again.

This can happen if the pulley is re-used more than once. Eventually it's too loose on the pump shaft and will walk off.

[mr_maxime]

Dave, what is the proper spacer for the DMCH alternator. PO owner used a nut but when I grabbed some calipers, I had 0.42" of space and the washer was slighter thicker. I grabbed a 10mm nylon spacer (. 42" is slightly larger) from ace to replace it temporarily.

I also had lots of broken belts and I think that oversized spacer had something to do with it.

[DMCMW Dave]

Dave, what is the proper spacer for the DMCH alternator. PO owner used a nut but when I grabbed some calipers, I had 0.42" of space and the washer was slighter thicker. I grabbed a 10mm nylon spacer (. 42" is slightly larger) from ace to replace it temporarily.
.

Normally there isn't one, there is a sliding bushing on the alternator. the fan-end bracket on the alternator should be right up against the cast bracket. BUT if someone has modified the bracket to make some other unit fit, all bets are off!

[David T]

The bracket holding the alternator also can be adjusted fore-and-aft. If you have changed the alternator it could have the wrong pulley for the belt. Or you could be using the wrong size belt. If you over-tighten the belt you can break the cords inside the belt and then it rolls over or flies off. First step is to make sure all of the pulleys are in the same plane. Next would be to make sure you have the correct belt and each pulley is correct for the belt. You also must check that all of the bearings are OK. If the bearings in the water pump or alternator are going bad it can cause the belt to come off. If you have spacers on the alternator, the better, cleaner way to do it is to reposition the pulley on the alternator so you don't need to adjust the alternator. The crankshaft pulley sets the plane, the water pump pulley must be aligned with the crank pulley and then the alternator pulley must align with the crank and water pump. Use a laser or a string to check the pulleys. A Vee belt must NEVER ride on the bottom of the vee, it must contact each pulley ONLY by it's sides. If the bottom of the belt touches the bottom of the pulley's vee you either have the wrong belt or the wrong pulley. If the belt is shiny on it's sides, it is slipping, that means it is too loose, a bearing is bad or it is riding on it's bottom. If a pulley is rusty or bent it can throw belts so carefully check each pulley.