S4 TII eats alternator belts every ~15min
 

Weird thing. The S4 I'm working on currently eats alternator belts every few drives. It has an exhaust leak of some sort, but I don't see how it could melt (the belts are melted) alternator belt, since it goes nowhere near the exhaust. Is there anything else exhaust wise that could leak and put hot exhaust around the alternator belt's path?

Thanks,
-Phil

Wrong tension?
Pulley warped?
Alternator misaligned?
Bad batch of belts?


-Ted

The belt is failing from heat. Reasoning behind this is that the belt shows heat fatigue on the teeth, and melts / splits as the failure.

Wrong tension, bad batch of belts are out because it's happened to 3 belts so far, 2 from napa, one from advance.

Alternator misaligned is out since we've pulled the alternator and replaced it twice (once between each belt eating). Not sure about pulley warped, I'm going to go check that in a bit.

I'm pretty sure the exhaust leak has something to do with it since exhaust leak = heat, and the belts seem heat fatigued.

Any ideas where the exhaust leak can come from? I'm going to dump some seafoam into the intake tract to try to find where the leak is.

Another thing to note. The ECU fried at one point. No reason at all. Replaced the ECU and it ran again, and happily ate another alt. belt.

Directly underneath the alternator is a significant amount of carbon. Ditto for underside of the alternator. This continues back for a few inches, couldn't see past that. Looking at several exploded diagrams, I can't see anything exhaust related in the area. Hm.

If I'm reading the diagrams right (I'm not very knowledgeable about the rotary) the only thing in the area exhaust related is the EGR valve. In fact, it looks pretty close to where all the carbon buildup is.

Did you put the alternater spacer in correctly or at all when you installed it?

Maybe your alternator is not spinning freely and burning the belt?


Pullies have a kink or nick somewhere?

Still suspecting pullies misaligned.

On an S4 TII the EGR valve is not anywhere close to the alternator. It is on the rear of the intake manifold. I think you are looking at a diagram for the n/a engine. The EGR for an n/a is behind the alternator on the center iron.
Has the car been sitting unused for a while? Rust on the pullies can eat belts pretty quickly.

its not exhaust, are you sure its carbon and not rubber buildup from the belt slippage?

the belt is probably hot because of friction, either hte pulleys are not aligned properly or not turning freely.

someone else already mentioned the spacer, it sounds like the spacer is missing or in the wrong place, this photo shows the proper placement for the alternator on a FC:

http://pengaru.com/~swivel/cars/rx-7...w_IMG_2794.JPG

Note the cylindrical spacer at the back side of the thermostat/water pump housing, between the alternator mounting ear and the thermostat housing... it's free to fall out when you remove the bolt.

Im on belt #3 out of maybe 20 hours of driving time. Yours sound about like mine, they look melted or failed from heat but I assure you its not an exhaust leak causing it. Slipping belts cause a shitload of heat. Same with mis aligned belts. Im going duel belt setup as soon as possible. Mine look aligned correctly from what I can see and I tighten them enough so that I would think they wouldnt slip, but I guess under hard accel. they still do slip. Id say you might have to buy a duel pulley to fix it for good. Unless someone else knows a way to fix this problem otherwise. A way you can tell if they are slipping or not is if you have black residue or powder all over stuff near the alternator. Thats parts of the belt that have worn off from slipping on the pulley. If yours doesnt have that then I have no idea. But there surely isnt enough heat from the exhaust near the belt to cause it to melt. So you either have gotten bad belts or something else is wrong

"In fact, it looks pretty close to where all the carbon buildup is."

Just saw that, so yeah that probably is your belt leaving that residue. So its either slipping or misaligned causing it to rub and wear a hole through the belt. One it slips once on a small section of the belt and it gets a worn spot on it, itll continue to slip there because it will have less material, and over time itll evenutally wear it all the way through there, making it look almost melted from all of the friction

If you've removed accessories and now have a single belt covering your water pump & alternator, it's possible your belt is slipping... this is especially true if you still have the mechanical fan and a single belt setup.

You can get a dual belt pulley to fix it like you mention, which increases the coverage but still leaves the water pump pretty poorly engaged even with two belts.

There is a "Yahoo belt" solution where you get a short belt and force it onto the water pump extra sheave with no adjuster, this resolves the belt slipping on water pump problem, search for yahoo belt IIRC should turn up the length.

There is also another solution, if you have no power steering or air conditioning on the car, you can relocate the alternator to the drivers side of the engine, and run a single belt. By relocating the alternator to this position, the single belt coverage on the water pump pulley is more than doubled without significantly hurting the coverage on any of the other pulleys...

like this:
http://pengaru.com/~swivel/cars/rx-7...w_IMG_3899.JPG

Yeah, I only have the alt. being driven and mechanical fan, but itll be gone soon. I can afford the $8 a belt for now until I think about the pulley. Everytime I get some cash to throw around i always forget about the double pulley until Im broke again. Ive got a/c but it isnt hooked up but will be next summer, so the alt relocation is off the play book. Im tryin to think in my head what sheave the a/c runs off of. Is it the other one that the double alt pulley will use? Maybe they make a V belt that long

considering the price of the double sheave pulleys and how most of them are underdrive, i'd probably just go the yahoo belt route, it works fine just a little bit of a pain to put on an remove :)

the ac and ps get dedicated sheaves that add onto the normal 2 sheave crank pulley setup, the 2 base belts both contact opposing sides of the water pump normally, but one goes to the air pump and the other goes to the alternator. you get rid of the air pump and you're left with one belt barely on the water pump...

you couldnt just run one long belt to the AC or PS and have it go on the water pump, it won't align... the AC and PS pulleys are farther forward so they line up with the add-on sheaves those options got placed on the crank.

what i was saying is, does the a/c has a dedicated sheave or does it share with the alt or anything. i cant remember just off the top of my head. either way im probably just gonna go the simple route and get the double sheave at pulley. wether or not the a/c can stay doesnt matter. If it has to come off it can.

If not that ill go serpentine belt system

maybe I wasnt clear..

Both the AC and the PS get dedicated sheaves @ the crank, they don't share with the alternator or water pump.

its because the AC and PS are both optional accessories, if you got an rx7 with no PS and no AC your crank pulley would have only two sheaves on it... the two sheaves on the end of the crank pulley in a car with AC and PS are removable, they just stack on.


For the original poster, does the car still have a functioning air pump?

i understood what you said. but again, what i was saying is when you get the double sheave alt pulley, the new extra belt, isnt it driven off of one either the a/c or p/s sheave that is on the main pulley? so wont one of them have to either be deleted or a longer belt installed?

The double sheave alternator pulley is used when your air pump has been removed.

You will have a sheave empty on your crank pulley (not the AC or PS one, but the 3rd sheave in from the front) and empty on your water pump pulley (the furthest forward sheave). These are where the new belt goes, taking the air pump belts place.

If you still have your air pump, and thus its belt, you have no need for a double sheave alternator pulley...

air pump will be gone very soon. only reason im asking is cause i dont have the belt layout right here in front of me. if i could see it id be ok. so i guess im just gonna go alt pulley and be done with it

Have you given any thought to actually replacing the alternator? It could be a bearing that tries to lock up when hot, but spins okay when cool.

FC alternators are a dime a dozen used...I used to have a stack of 10 or 20 of them that I couldnt sell. IT's worth picking up a spare or 2 if you're having issues.

You may also be overtightening belts.

now thats a hungry alternator - hehehe

Bring it to a shop or ask a mechanic or knowledgable personel to check it out. It's obviously out of your knowledge what's going on.

The best advice I can give.

Guys I know this thread is old too. I am spending my time searching instead of posting.
89 NA, just check the sig. All I have are a CorkSport exhaust and a yoohoo belt aside from my internal work.
I fry alternator belts often as well. REPLACING the alternator did nothing. Removing all electrical load - in or out - makes it run fine. WITH electrical loads applied [plug connector and B terminal] the belt will howl and smoke even at idle; without either, it doesn't make a peep even at 9000 rpm whether held or forcefully revved. I checked pulley alignment before and after replacing the alternator with a laser line for construction to reveal perfect pulley alignment on both. The belt is new, and a Bando 2320. I left the new alternator on, because well, why not? It's brand new, not even reman. My yoohoo belt has deflection, and these tests on the alt belt were done all between 1/2" and 3/4" deflection as per the spec in the FSM. Stumped, and really not trying to go dual sheave if at all possible. I live a long way from a parts store, or even most of civilisation, so I like having the yoohoo belt as peace of mind. Also it's gotten me 20+ miles home without a peep from the motor twice now, so I'm down to keep it.
Should I be checking continuity in the B terminal? With the key to just on, I don't get all my lights, just the ones that I'm using; while working on it I would get hatch, brake, door, washer [because my rear reservoir is empty] and the check engine light. The rest come on, but very dim. I'm stumped and I can't keep getting jumped off, as this is my daily.