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View Full Version : Belt sliding on edge of vacuum pump and crank position sensor



Shuck
05-27-2007, 18:40
As a fellow sucker for punishment, I just bought my 3rd 6.5TD. It's a 95 K2500 with 159k miles.

When I bought it, it had a service engine light and needed to be cranked 15+ seconds to start. It was also VERY noisy, which I suspected to be poor timing (probably due to whatever was causing the SES light) but it ran smoothly once started and has good power. The owner had also just replaced an oil cooler line because the serpentine belt broke and cut one of the oil lines.

I took the truck to a local diesel shop to have the timing checked and the codes read. The only code was a crankshaft position sensor code and the timing was way out of whack. They did a quick TDC learn and the engine quieted down a LOT to much more normal levels, but we decided to wait to do a proper timing adjustment since it was a lot of work just to get the truck started (starter was actually smoking). Once the code was cleared, the truck starts much faster, but still kind of stumbles through the start process.

I haven't replaced the crank position sensor yet because I'm not 100% sure it is faulty (and they are like $80.) In continuing to operate the truck for a few days to shake it down, I noticed that the serpentine belt was starting to wear on the non-grooved side about 1/8" in from the front edge. Upon observing the belt with the engine running, I discovered that while the belt was turning, it was actually riding up on the front lip of the vacuum pump pulley. I'm not 100% sure which part to blame for this.

I took the belt off and rotated all of the accessories. They all rotate freely, except the vacuum pump, which increases in resistance until a point and then releases the resistance. I think this is how it's supposed to operate, but it does seem to require me to turn it pretty hard to get it "over the hump."

When the belt is installed, it appears to line up with all of the pulleys except between the crank pulley and the vacuum pump. It appears that the crank pulley is slightly forward of the vacuum pulley. The vacuum pulley and A/C pulley seem to line up fine. The crank pulley and water pump pulley seem to line up fine, so I'm a little confused. If I were able to move the vacuum pulley forward about 1/4" I think the problem would be solved, but it makes me wonder if there isn't a bigger problem.

The previous owner didn't exactly maintain the truck well. It also has 4.10 gears which means this engine has gone around as many times as a truck with 3.73s and 200k miles.

If the crank pulley and/or harmonic balancer needed replaced, would the pulley slide forward like that? Would a bad harmonic balancer cause a crank position sensor code? How hard is it to replace the harmonic balancer, crank pulley, and crank position sensor?

I'm thinking that I should probably replace the harmonic balancer due to the age of the engine and the potential crank problems they can cause. Schuck's Auto parts has one with the crank pulley for $109.

Any experts care to speak up on what they think might be happening here?

Thanks!
Ryan

More Power
05-28-2007, 11:50
I'd pull the vac pump, to get a better look at it. I'd first suspect the VP as the cause of the belt problem. The actual pumping mechanism works like you described, in that an elliptical lobe on the VP shaft rides against the diaphragm of the vac pod. Look to see whether the shaft and its bearings are OK, the pulley is OK (i.e not moving forward on the shaft) and that the pod generates the typical 18-22 " of vacuum with the engine idling. The needle of the vac gauge will jump around somewhere between the numbers mentioned, which is normal.

Jim

Shuck
05-28-2007, 19:54
I didn't pull the vac pump yet, but did push around on the pulley with the belt off to see if it was loose. It seems to be solid and I can't come up with a good reason why it would have worked its way towards the pump. The belt is riding on the front lip of the vac pump pulley - closest to the radiator. I have ordered a new harmonic balancer / pulley because of the number of people with 95s who have had broken crankshafts. Is the harmonic balancer hard to change out?

I figure I'll change that out, since it's peace of mind anyway and see if anything changes.

rameye
05-29-2007, 04:27
The pump may have been replaced recently...It takes very little time for the new pump to look old...especially if the pulley was reused.

Anyway, upon reinstalling the pulley it is possible to slide it too far back or forward if you dont use the old pump for reference. I had to adjust mine to center the belt in the pulley after install. Just plain forgot to reference the old pump before I tossed it.

keep at it...stare at it enough..you'll figure it out.

Shuck
06-04-2007, 22:28
How hard of a job is it to replace the harmonic balancer? I had to work this weekend, so haven't had a chance to remove the vac pump and adjust the pulley yet. I'm just wondering about the harmonic balancer since so many people blame borken cranks on them. Will I gain anything (peace of mind) by replacing it?

Ryan

rameye
06-05-2007, 12:51
I have a 95 also...I pulled mine off to do the timing chain (way overdue) and it was fine... However you really need to pull it to get a good look at it.

Anyway, it came off very easy...mighta been the easiest part of the job.

Shuck
06-30-2007, 20:27
Update:

I replaced the crank pulley/ harmonic balancer and also removed the vacuum pump. While I had it off, I turned it and it seemed to turn ok. I used a puller and moved the pulley out almost a full 1/2". The belt STILL walks up the edge of the pulley. As a matter of fact, now it skips over one groove on the A/C compressor after a few minutes of driving. Could there be a part missing or a bracket bent?

Ryan

Shuck
07-02-2007, 15:37
Update:

Replaced the tensioner pulley. Same results. I currently have the vacuum pump off and am going to try going vac-less with a 101" belt and see if it still has the problem. If it doesn't, I'll probably be looking for a turbo master. Any other ideas?

Shuck
07-02-2007, 16:17
Update #2 for the day:

I removed the vac pump all together and bought a 101" belt. Works like a champ now, except I have no boost until my turbomaster gets here =).

Aaargh, why is the vacuum pump such a PITA on these trucks?

I took it in to our local auto parts store which is staffed by about 7 older dudes who have lots of experience with cars. When I told them what was happening and what I had already done to try to fix the problem they were all dumbfounded. Finally I told the guy I'd just take a belt that was 1" shorter and leave the vac pump off. He looked at me kinda funny, but got it for me.

Well, my entire serpentine system has pretty much been replaced at this point. I guess it should be good to go for quite a while longer. The only thing I can come up with is the guy who owned the truck before me managed to bend the vac pump while replacing the water pump (which he did right before I bought it). Who knows.

rameye
07-03-2007, 17:40
cant help but wonder if it was reinstalled wrong...

I have to admit, the vac pump was one of the last things I had put back on after 6 months of having it off....I was attempting to deflect the pump in order to make the wrong bolt fit in the wrong place....

Sanity finally struck before I reached for the breaker bar......so I could see how the pump could be deflected.. or the bracket.....wouldnt take much deflection to get that belt sliding...much like a belt sander adjustment.

maybe??

twaddle
07-04-2007, 00:09
Hi there,
Have you tried turning the pulley on the vacuum and see if the pulley is aligned ok or if is out of alignment. Check for up and down (shaft bent???)
and sideways for want of a easier way to put it.

The pulleys are not cast material but pressed steel and can be easily distorted during Removal & Re installation.
Also try and check if the mount bracket is square. You may need to try running a straight edge or using a piece of string across the faces of the pulleys to try and find which one is out of square. You would need to rotate each pulley to check for alignment.
Just a last point, have you tried watching each pulley when the engine and the vacuum pump pulley, which is suspect, when the engine was running to see if there is any misalignment to be seen? If there is no visible misalignment then it could be a mount bracket.

Good luck

Jim
Biggar, Scotland
soon to be Alberta, Canada

Shuck
07-04-2007, 11:45
I spent a good hour watching the belt run around the different pulleys to see if one of them was wobbling or acting funny. They are all pretty stable, but the belt was always a little squirrely on the vacuum pump. The vacuum pump pulley itself doesn't wobble or shake and the shaft doesn't have any play. I'm pretty sure that when they reinstalled it during the water pump replacement, they either left something out or bent something on the pump itself.

As I looked at the belt when the engine wasn't running, it almost looked like the vacuum pump was bent downward.

For now, I've just decided to go vacuum-less and it seems to be working fine. Hopefully my turbomaster will get here by this weekend so I can have boost again.

Shuck
07-04-2007, 11:48
Now on to the crankshaft position sensor. I found a new one at the local auto parts store for $46. BUT when I went to remove the old one, the bolt started to round off!!! It's not completely gone yet, but my 13mm socket doesn't hang on for long before it starts to slip. Any ideas on how to get that bugger out of there? I didn't think it would be quite so tight. Not a lot of room to get a stud remover or something like that on it.

twaddle
07-05-2007, 02:35
Hi Shuck,
Be sure that the socket required is a 13mm, if the 13mm skt is a bit loose try a 1/2 inch which is a smidgen tighter.
Also use a "hex" (six sided) socket as it is less likely to round off the corners on the Crank position sensor bolt, instead of a 12 point socket.
If the bolt head is not too deep/thick a socket can slip off it as there is usually a taper on the inside entrance into the socket, I have on occasions ground off the face of the socket to get rid of the taper part so the socket gets a good grip on all of the bolt head.

Good luck

Jim
Biggar, Scotland
Soon to be Alberta, Scotland

Shuck
07-05-2007, 19:23
Jim,

I'll try to find a 6 sided socket and make sure the hex end is flush with the edge. I was wishing I had a socket just like that while I was doing this - guess I'll have to find one. I'm 99% sure it's 13mm. I tried a 1/2" and it wouldn't go on. I guess if push comes to shove, I'll move the power steering pump out of the way and hammer on a 1/2" socket (planning to lose the socket and the bolt). I've been spraying the bolt with panther piss (PB Blaster) daily for the last couple days to help break it free.

Ryan