Belt tensioner question

[Corvette95]

Got my engine back together last night, - fired up, belt tensioner is jumping around and making a "clicking" noise when it does. It was doing this before I torn the car down. I sent my tensioner to Marc H for rebuild. Belt is routed right and I used a NOS correct Goodyear belt, anything to adjust or check besides then tensioner - I would assume it is the internal tensioner spring? Also, I know the tensioner can be mounted incorrectly - hard to do but possible, mine is installed correctly. Any thoughts

[WARP TEN]

Got my engine back together last night, - fired up, belt tensioner is jumping around and making a "clicking" noise when it does. It was doing this before I torn the car down. I sent my tensioner to Marc H for rebuild. Belt is routed right and I used a NOS correct Goodyear belt, anything to adjust or check besides then tensioner - I would assume it is the internal tensioner spring? Also, I know the tensioner can be mounted incorrectly - hard to do but possible, mine is installed correctly. Any thoughts

I am guessing you may have already done this, but I would suggest a call to Marc since he rebuilt the tensioner. --Bob

[lfalzarano]

The belt MUST be correct length for the tensioner to be in middle of range with no hitting either extreme limit, the stronger spring has much to do with that too. If you can push the tensioner arm by hand the spring is too weak even if the part is new.


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[Corvette95]

I am guessing you may have already done this, but I would suggest a call to Marc since he rebuilt the tensioner. --Bob

I sent him an email, thing is, I trust HIS work over mine, but everything seems good on my end other than the tensioner jumping

[Corvette95]

I couldn't upload a video so I used a hosting site. hope this link works...
https://streamable.com/3ix64s

[We Gone]

I hear some noise when the AC compressor cycles, turn off the AC first than check noise. You can also remove the belt and and see what you hear. wont hurt anything as long as you just start check and shut off.

[Dynomite]

What is gap between belts compressed by Tensioner??
Maybe a shorter belt would help??
I think the tensioner jumps around more with a longer (more loose) belt where the pressure applied by the tensioner is less as the tensioner is unwound and the tensioner being pointed directly perpendicular to the belt.

The belt appears too long as the tensioner has deflected the belt considerbly.

[secondchance]

Corvette95. Have you replaced alternator lately? If so, verify if the alternator pulley is correct size. Often, L98 pulley is on replacement. If so, belt ends up being a tad longer and could result in tensioner bouncing around.

[Corvette95]

I have been checking, belt is correct application, I took a stethoscope to all the bearings including a/c, noise abnormal noise other than the tensioner. I measured the alternator pulley (this was the alternator that was on it when I bought it - I had it rebuilt while it was off just in case) , was suggested may be an undersized pulley, it is 2.4 inches wide (alternator pulley) . I can pry on the tensioner to keep it from jumping around and the noise goes away. https://streamable.com/ahuq0d

[Dynomite]

Belt is too long :p

https://cimg8.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/600x600/80-img_1456_9e581cd3080c47731e121da09ed641470e70f4be. jpeghttps://cimg1.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/600x600/80-img_1454_db7fe2934a93b8b8acf1a0ff59a96f712f281ab5. jpeg

[Corvette95]

Belt is too long :p I have double checked the part # . Plus the tensioner was jumping with old belt, that is why I sent the tensioner for rebuild. I need to make sure the pulley is correct on the alternator at this point. It is 2.4 inches across.

[secondchance]

For what it?s worth, GM OEM belt, I believe, was 80.375?. When new, these belts required walking the starter to install because they were so tight. Some replacements are 80.5? and would slip on while tensioner is held down. Not all, but a lot of fan belts? part number indicates length. xxx805 would mean 80.5? for example.
What brand fan belt are you running?

I had a similar issue and eventually figured out alternator I replaced had L98 pulley. Replacing the pulley solved the issue. Since then I went with high output hair pin alternator with 2.2? pulley. This meant going to 80? belt.

For some reason apostrophes and inch symbols are showing up as question marks. Weird...

[Corvette95]

So I put a 3/4 inch smaller belt on it. Had to bump the motor to get it on. I don?t think there is an undersized pulley on it. The tensioner way heavy loaded with smaller belt, it still shook but no noise from tensioner. There is however, some minor noise from the metal fans of the alternator hitting the pulley or something, just ?barely? . So I know I will have to replace alternator (please tell me the quickest way to do this with plenum on, I read the factory manual way that says pull the water pump pulley and oil sender , but even after this , I am not going to leave the smaller belt on it because I think it is much too tight. Thoughts?? I measured the pulley and it seems to be stock size at 2.4 inches. For what it is worth I put a Gates K060795 Outside Length (mm): 2034mm

[A26B]

I have double checked the part # . Plus the tensioner was jumping with old belt, that is why I sent the tensioner for rebuild. I need to make sure the pulley is correct on the alternator at this point. It is 2.4 inches across.

Stock Alternator Pulley Dimensions

https://cdn10.bigcommerce.com/s-nkg90o/products/1048/images/2760/ZR-1_OriginalAltPulleyDimensions__60481.1592007348.12 80.1280.jpg?c=2

[Corvette95]

Thanks Jerry, mine measures 61 mm across. I don't know if that is the L98 pulley or not, but got to replace the alternator. I will make sure the new one is to these specs and put the A/C Delco belt back on. I only drove this car ten miles before I started the restoration.

[Corvette95]

If my current alternator nor the new alternator comes with the spacer bushing, where can I get one and what is the size? I am figuring the one that is on the car is missing the spacer which is why the fins are lightly scraping the case.

[Jagdpanzer]

What is idle RPM?
Appears in the video to be low.
Try increasing the RPM to see if it improves things.


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[Corvette95]

This was a quick start up check for oil/fuel/coolant leaks (hasn't been started since mid January). I had not set the idle or adjust TPS yet, the idle is off but that was to be expected. The tensioner still rattled at higher rpm until I put the smaller belt on it. I am going to replace the alternator because I believe it doesn't have a spacer and the fins are lightly rubbing plus the pulley seems to be about 20mm too small. I just hope the new alternator has the spacer. I guess the rpm was around 800 but it did drop with a/c cycle. Dash and interior is still out so no gauges. Goes to the paint shop when I get the motor together so it can be moved around. Thanks

[Flyman 27]

Working on my alt as well. My fan was rattling as well. Turned out to be the fan barely nicking the intake, just enough to ring like a bell.
Installed a spacer behind the fan to reposition it a little and now it misses.

[Corvette95]

Working on my alt as well. My fan was rattling as well. Turned out to be the fan barely nicking the intake, just enough to ring like a bell.
Installed a spacer behind the fan to reposition it a little and now it misses.
What spacer did you use if you did not have the OE one?

[Flyman 27]

I used a couple 16mm machine spacers I got at Ace hardware.

[Corvette95]

So just finished getting old alternator off. It seems the spacer is built into the pulley, it is a hair thin at 3mm. The diameter of the pulley is 60 mm. I am going to pick up the new alternator. Should I remove the pulley and check for a spacer if the pulley dimensions are correct? TIA

[A26B]

https://cdn10.bigcommerce.com/s-nkg90o/products/1049/images/2763/ZR-1_OriginalAltPulleySchematic__97597.1592059615.128 0.1280.jpg?c=2


Some correct pulleys will have the Front Collar 0.396" spacer made integral with the pulley, so verify what you have. before adding the 0.396" spacer.

Make sure the Back Collar 0.232" spacer is behind the fan. Without it, tightening the bolt will warp the fan & the pulley will slip. Some have not noticed the Back Collar as being removable when changing their stock LT5 pulley over to a new alternator with a smaller pulley. The nut will tighten but the pulley force against the fan will warp the fan blade until it rubs the alternator. Bending the blades only adds to the problem of the missing Back Collar.

[Corvette95]

Thanks again Jerry. I looked on your site and found the pulley info, obviously I looked in wrong place for the spacer info. I also saw you were out of alternators, you show one pulley in stock but no option to put it in my cart....do you have one before I order the Summit pulley? On ANOTHER NOTE, I did special order supposedly a correct alternator overnight from Oreilly's. Just went to pick it up with digital micrometer in hand....they FORGOT to order it, now it will be Tuesday. If you have either the pulley or a whole alternator Jerry, I would certainly order it from you. Let me know, you have my email and # . Thanks!

[Corvette95]

The inner spacer was intact and correct size on the old alternator, the pulley although had no spacer but was offset made into the pulley 3.02 mm. After disassembly I could see light strike marks ) from the fan blades to the fan blade cover (that this particular alternator had).

[Corvette95]

Corvette95. Have you replaced alternator lately? If so, verify if the alternator pulley is correct size. Often, L98 pulley is on replacement. If so, belt ends up being a tad longer and could result in tensioner bouncing around.
Just to follow up on your post, not only was the pulley undersized, spacer dimensions were wrong, causing faint contact intermittently with the fan blades to alternator. The car was nice, low mileage when I bought it but the owner was not a wrencher. I a lot of things were not right on the car, I HAD to save it. I am very very compentent in C4's mainly electrical and driveability, Never had much mechanical done to my 95 Lt5, what little was done was at Sought Georgia corvette, so I am in a heavy learning curve, not in the systems designs but the little nuonces of the LT5 such as this alternator spacer. I need to do this with my hands, only way to learn, but it is a back killer and ever worse when you complete a system only to take it back down again for a small rubbing noise..aka alternator spacer issues. Thanks to all that have helped, I know I have asked for a lot but please remember, I bought this car, drove it less than ten miles home a took out every major system in the car to fix botched previous work and to perform an NCRS quality restoration- a lot to take on. I rely on the group to help and you have, and I will have more to come but I did get it running fine other than a few tensioner and alternator noise after full top end port, hoses, thermostat housing, oil filter adapter, heater core, steering column, all new brakes, brake booster, secondary rebuilt, fuel pump-both..and on and on, interior is dead empty, no seats, dash, carpet, gauges etc. This is all at one time. Getting this engine completely, install steering wheel, bleed all new brakes and I will be able to move it to paint shop , after that rebuild continues. Pics to follow but I promide it to be showroom new. Spend two weeks with a toothbrush detailing under carriage. Hot tired and frustrated today but I am saying a low mileage 90 from death for a full future ahead....using NOS whenever is possible as well.

[A26B]

Thanks again Jerry. I looked on your site and found the pulley info, obviously I looked in wrong place for the spacer info. I also saw you were out of alternators, you show one pulley in stock but no option to put it in my cart....do you have one before I order the Summit pulley? On ANOTHER NOTE, I did special order supposedly a correct alternator overnight from Oreilly's. Just went to pick it up with digital micrometer in hand....they FORGOT to order it, now it will be Tuesday. If you have either the pulley or a whole alternator Jerry, I would certainly order it from you. Let me know, you have my email and # . Thanks!

No, you didn't look in the wrong place. I had to pull it up from my files and put it in Jerrys Gaskets/my photos. Sort of like my own personal photobucket to host them.

I don't have pulleys & spacers in stock or for sale.

We are out of Alternators and do not plan to re-stock since REMY sold out and the company has changed hands a couple of times.

Likewise for Starters. I think I have 1 or 2 left in stock & when those are gone, we will not be re-stocking.

They are available from other sources as you are finding out and the pulley can be swapped over from the original LT5 Alternator (in most cases) I do have new LT5 Alternator Pulleys on my list of parts to make, but not anytime soon.

I have accumulated quite a few cores of different parts with possible plans to rebuild them myself, but like so many other project, I really don't have the time or the stamina. Getting old has slowed me down on work, but not on speed!

[Dynomite]

Another Alternative for Alternator Pulleys :thumbsup:

Post 250 - All Aluminum Alternator Pulley (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-13.html#post1592505495)

https://cimg2.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/400x400-1/80-992f36c2_d357_4f2c_9918_b3ac31b4ab6b_1__70901d2d6f 7aaeb69783cf2f3178d4df14e6932f.jpghttps://cimg5.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/400x400-1/80-36a4d85d_9179_4855_b52d_0d4b50df52c5_1__516d311138 81d4521481cb354611c3eb3fde9235.jpg
https://cimg1.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/800x800-1/80-d8a219b2_f604_4653_9c28_360157f1027b_dfc4de44d3470 aa8be51a2fe18ec298d236e0441.jpg

[secondchance]

Another Alternative for Alternator Pulleys :thumbsup:

Post 250 - All Aluminum Alternator Pulley (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-13.html#post1592505495)

https://cimg2.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/400x400-1/80-992f36c2_d357_4f2c_9918_b3ac31b4ab6b_1__70901d2d6f 7aaeb69783cf2f3178d4df14e6932f.jpghttps://cimg5.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/400x400-1/80-36a4d85d_9179_4855_b52d_0d4b50df52c5_1__516d311138 81d4521481cb354611c3eb3fde9235.jpg
https://cimg1.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/800x800-1/80-d8a219b2_f604_4653_9c28_360157f1027b_dfc4de44d3470 aa8be51a2fe18ec298d236e0441.jpg

I?m running this aluminum pulley. Looks very pretty mated to billet aluminum, high output alternator.:cheers:

[Corvette95]

Thanks that is what I ordered. I figure the new alternator will have wrong pulley.

[Corvette95]

I?m running this aluminum pulley. Looks very pretty mated to billet aluminum, high output alternator.:cheers:

Confirming the Summit Pulley does not need ANY spacer between the fan blade and the pulley. The Summit has the built in lip on it. Right now I have the housing the inside spacer which is correct size, then fan, then stock alternator with wrong size came with a WIDE spacer unlike the one it replaced..both had an L98 pulley on it, so I install the summit directly on top of the fan blade?

[Corvette95]

My two spacers choices if needed between the blade and pulley are 10.2mm and 5.72mm. Do I need either between fan and pulley..side note, this new alternator came with a round circular disc protecting the fan blades (thin round disc- I am NOT going to use that)

[Corvette95]

https://cdn10.bigcommerce.com/s-nkg90o/products/1049/images/2763/ZR-1_OriginalAltPulleySchematic__97597.1592059615.128 0.1280.jpg?c=2


Some correct pulleys will have the Front Collar 0.396" spacer made integral with the pulley, so verify what you have. before adding the 0.396" spacer.

Make sure the Back Collar 0.232" spacer is behind the fan. Without it, tightening the bolt will warp the fan & the pulley will slip. Some have not noticed the Back Collar as being removable when changing their stock LT5 pulley over to a new alternator with a smaller pulley. The nut will tighten but the pulley force against the fan will warp the fan blade until it rubs the alternator. Bending the blades only adds to the problem of the missing Back Collar.

Jerry, do you have dimensions from the outer pulley edge to the face of the fan blade.

[Corvette95]

Here are pics

[Corvette95]

So with the summit pulley, the outer spacer is not needed? The bearing mounts flush (the bearing has the offset) against the fan?


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