VR6 - Intermittant screech/grind from Alternator driive belt

[black66 0]

Hi,

 

My VR has just started an intermittant sqeak from the alternator drive belt end of the engine(once every 1 to 5 seconds).

My initial thoughts were alternator bearings, but sound seems further back than the alternator.

Does anyone know if the tension of the belt is adjusted by an eccentric tensioning wheel(similar to cam belt tensioner on 16V KR engines). Because I can see what looks like this on the side of the block.

Anyone had simlilar trouble or can shed some light on this subject.

 

Dave

 

Oh, and while I'm here, where and what is the brake pedal position sensor? This is showing as a fault on VAG-COM ( code G100). Does this have any drastic effect on braking?

 

Ta very much!

:) :) :)

[dr_mat 0]

Sounds like you need a new aux belt tensioner... That and the water pump are the most common failings on the aux belt components.

It might also be worth sticking a new belt on there, to see if you've just got a glazed belt slipping somewhere.

[stormseeker 0]

For VR6 belt tensioner info see http://the-corrado.net/.archive/forum/viewtopic.php?t=7833

 

Brake pedal posintion sensor won't affect braking performance, just stop the ABS working if the brain decides it's duff -- see http://the-corrado.net/.archive/forum/viewtopic. ... torder=asc for location, part number etc.

 

:-) :-)

[Henny 0]

Ah! Brake pedal position sensor? Kev's just had that one and sorted it IIRC...

 

See HERE for details... 8)

[Kevin Bacon 5]

I'd say the water pump is the likely suspect for your squeak. Mine started squeaking just before it burst it's internal seal.

 

As for Brake Pedal sensor, it's a bit of a git to replace but I'd replace it. It's what decides how hard the ABS pump works, i.e. pedal pressed hard, more pumping pressure. The problem is, if the sensor is knackered, the ABS pump won't be able to tell the difference between a slight lock due to wet grass of a full on emergency stop on tarmac.

 

Change it ASAP.

 

K

[dr_mat 0]

Didn't think the pedal position sensor was anything more than an on/off switch? But it's still useful for the ABS system. If you have uneven road wheel speeds, and it doesn't know whether you're braking or accelerating, it doesn't know whether to ABS or attempt to lock the wheel..

[Kevin Bacon 5]

No it's more than that. It monitors the travel of the pedal, hence, erm, it's name!

 

How does the ABS know A) know when to kick in and B) at what pumping force?

 

A) Wheel sensors

B) Pedal position sensor

 

The ABS pump is progressive and the PPS prevents the ABS pump working flat out on a wheel that's locked doing 5mph on wet grass or sand when all that's required is a few cadence pumps at moderate pressure. And also at the other end of the scale, you don't want half-hearted pumping when you're doing an emergency stop from 70mph.

 

K

[black66 0]

As an afterthough....

I'd plugged VAG COM in as my ABS light had come on. Shows front left wheel sensor needs replacing.

Brake pedal pos sensor wouldn't just be showing due to this would it? I know some things on VAG COM give a red herring.

 

 

How tricky, and how much, is water pump replacement should it be that?

I'm off to remove my serpentine belt to investigate the other problem further.

 

Cheers for your help so far.

 

:D

[black66 0]

UPDATE.

 

Removed the serpentine belt. Tensioner nice and smooth, no play.

Lots of play in the water pump.

Started the car without the belt on and it is infinitely more quiet than with the belt on.

Gotta be the water pump! :shock:

Got a bit worried until I searched the forum for details and as usual, kevhaywire comes up trumps with a replacement procedure somewhere on the forum.

 

Thank you very much.

 

Can't wait to get a nice quiet pump on!

In the meantime just have to keep fingers crossed and use the AA if I have to.

 

Kev, did yours expell all the coolant instantly after the seal blew?

 

Cheers again

 

:D :D

[Kevin Bacon 5]

The ABS brain isn't notorious for leading you up the garden path, unlike the Motronic engine brain.

 

If it says a sensor is out, then it is.

 

Water pump is about £20 from G&S, a bit more from VAG. The only difference is the VAG pump has a plastic impeller and the GSF one has a metal one. I used a GSF one on mine because VW couldn't get me a genuine one quick enough, and it's fine.

 

Swapping it out is about 2 hours work including refilling with coolant.

 

Once the belt is slackened, turn the tensioner, alternator and pump pulleys by hand and see which squeaks.

 

K

[Kevin Bacon 5]

Kev, did yours expell all the coolant instantly after the seal blew?

 

 

No it squeaked for about a week and then I found a puddle of coolant on the floor one morning!

 

There's a pressure relief valve inside the pump that vents coolant to atmosphere in the event of a seal failure.

 

You don't lose that much coolant, just keep an eye on the level if you can't change the pump this weekend.

 

When you do a coolant change, use only G12+ and fill up via the radiator top hose, not the expansion tank! I'll tell you more nearer the time but I've probably already done a guide for that somewhere too.

 

K

[black66 0]

Don't worry Kev. I followed your coolant refilling guide before when doing the thermostat housing, yet another common problem!!

 

Cheers

[Supercharged 2]

Tip for getting the BPPS out, pump the brake pedal first to release the vacum and use a mirror so you can see the clip underneath so you can release it with a small screwdriver