Oil light buzzer and brakes

Post by **chrisgentle** » 09 May 2012, 13:14

Hi there,
I have read all the various posts on the buzzer of doom and oil light but none match my issues.
I have a T25 1.6 turbo Diesel 1986. When I start it the oil light and buzzer comes on and I have no brake assistance. After about half a mile the buzzer and light goes out and my brakes work normally. Buzzer and light then only come on when I slow to low revs. Driving along at 50-60 no lights or buzzer. Drop to 40, buzzer and light. A friend of a friend has told me that the 'thing' that drives the oil pump is the same 'thing' that gives the brake assistance. Is this true and, if so, what is this 'thing' called and where is it located please?

Mechanical history that I have had done: New cam belt, new cylinder head, new turbo. Oil filter failed and dumped my oil, luckily only 200 yards from home. Fitted new (and correct) filter and had this problem ever since.

Any help on this would be greatly appreciated

thanks
Chris

Post by **Hacksawbob** » 09 May 2012, 17:50

The thing that gives brake assistance is the vacuum pump, the oil pump is above the long thin but that goes into the oil sump (oil pickup pipe) I think they are run off the same gear.

Oil filter failed

in what way did it fail?

Post by **colinthefox** » 09 May 2012, 21:47

It sounds like neither the oil pump nor the vacuum pump are rotating very well. They are driven together by the intermediate shaft off the back of the cam belt via a smooth pulley which can slip. There are two reasons it might slip

1 If the cam belt was loose or
2 If the oil pump or vacuum pump was stiff.

If your oil filter failed and dumped your oil, that might give a hint that there is something preventing the oil pump rotating, like a blockage perhaps. The vacuum pump is unlikely to be the culprit.

You can test the oil pump by taking off the vac pump, and rotating the oil pump (don't ask me which way) with a piece of 15mm copper plumbers pipe flattened to slip over the shaft. You should be able to pump up oil by hand and make the oil light go out.

You could also remove the cam belt cover and see if the back of the belt has been damaged by sliding over the intermediate shaft pulley.

Hope this helps

Post by **chrisgentle** » 09 May 2012, 22:12

Thanks both for your very helpful replies. As soon as we get a dry day (!) the vacuum pump is coming off.
The oil filter failed as the was a slight crack in it where the body meets the piece that screws off. When i took it off I noticed that it has distorted quite badly. I though maybe when it was originally put on it (not by me) it had been mechanically tightened which caused the distortion.

Anyway, I'll post the results of my investigation on here.

Many thanks again,
Chris

Post by **kit** » 09 May 2012, 22:15

The vacuum pump relies very much on oil flow mine dried up and almost seized after I ran low on oil.

Post by **chrisgentle** » 09 May 2012, 22:29

Thanks Kit. From what you and other have said and since I had the cam belt changed about a year ago, its is sounding more and more like the oil pump might be the culprit hence stopping oil flow, hence dropping oil pressure and, as an added bonus, interfering with the brakes via the vacuum pump.

If it does prove to be the oil pump at fault then this is accessible by simply dropping the sump off?

Chris

Post by **kit** » 09 May 2012, 22:45

From what I remember it is accessible from the sump, if you do need to replace it get one from Brcikwerks as I believe the GSF ones need a bit of adapting to fit?

Post by **kit** » 09 May 2012, 22:51

Sorry about the spelling

Brickwerks.

http://www.brickwerks.co.uk/shop?page=s ... ory_id=109" onclick="window.open(this.href);return false;

Post by **chrisgentle** » 09 May 2012, 23:00

kit wrote:Sorry about the spelling Brickwerks.

http://www.brickwerks.co.uk/shop?page=s ... ory_id=109" onclick="window.open(this.href);return false;

Cheers. If I need one I'll give them a call

Post by **Hacksawbob** » 10 May 2012, 07:08

Don't try and remove the hose from the top of the vacuum pump the plastic hosetail snaps for fun! If you need to remove the connection it might be best to cut the rubber connecting hose. Sounds like the the intermediate shaft isn't being driven at low speed. I would have thought there would be some squeal if the pump was refusing to turn due to a blockage.

Post by **chrisgentle** » 10 May 2012, 15:34

Thanks for the tip Hacksawbob. Going to have a look at it this weekend

Post by **chrisgentle** » 12 May 2012, 16:00

Ok, an update. It's been sunny so I've been abound the back of the van. Here's what I did:

Cam belt cover off. Start engine. all pulleys turning fine.
Vaccum pump off and this rotates freely.
Oil pump shaft rotates freely.
Tunrned over engine with vaccuum pump still off and the the toothed shaft that turns the vacuum pump and, in turn, the oil pump spins when engine is turned over.

Summary: It appears that the drive from the cam belt is turning ok, the vacuum pump is turning ok and the oil pump is turning ok......but still, when first started I have no brake assistance, an oil light and, after a few rev an oil buzzer. Then following a few good revs, oil buzzer and light goes off and brake assistance returns....if I had hair I'd pull it out!

Any more suggestion greatly appreciated.

Post by **kit** » 12 May 2012, 17:49

Ok, oil is the correct grade?
Vacuum pump could be worn out, mine used to work after the engine was revved but eventually it faded out (after months) completely, not sure how you can verify this?
Is there a non return valve fitted to the vacuum pump mine was not fitted and I had to get one.

Post by **chrisgentle** » 12 May 2012, 18:30

Yes, it's the right grade oil. Same as used by my local vw expert who always has vans in his workshop. Semi synthetic 10/40 for turbo diesel engines.

No, there isn't a non return valve. Excuse my ignorance, but what would that do? Would it retain pressure the brake side of the pump?

Post by **kit** » 12 May 2012, 19:07

I thought you needed mineral oil? And yes the non return valve keeps the pressure to the servo.

http://www.justkampers.com/shop/t25/ori ... em?cat=755" onclick="window.open(this.href);return false;

It lists for use on diesels as well.

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