940 Brake servo problem

[martin calva]

Quite suddenly my LHD 1994 940 estate has developed a problem that I assume is related to the brake servo.

Symptoms:

- Particularly at very low speeds, the brakes are much less responsive than normal although I have verified that with enough force on the brake pedal, the car will still halt qutie quickly at speed/

- When I start the engine with my foot on the brake pedal, the pedal does not move down towards the floor as it normally did.

I am assuming that there is a problem with the brake servo. I've booked it in to the local garage that specialises in Volvos for next week. Is there anything I should check prior to that? Thanks for any help.

Martin

[Laird Scooby]

Any other symptoms Martin? Bad idle, cutting out, poor starting or similar?

Could also be the hose between the servo and manifold (assuming it's petrol and not diesel) has collapsed internally or the NRV on the servo has failed. Worth checking all of that, split hoses etc too.

[TonyS9]

I notice this very slightly on mine, more so when cold, but not enough for me to consider it a fault. They just seem to need a harder press at junctions for the first mile or so.

Have you checked the calipers recently, the slider pins are prone to siezing.

[aardvarkash10]

vacuum fault.. Hard to tell from over here, but definitely a get-it-to-the-man job.

[martin calva]

Dave, thanks. It's diesel. Starts 1st turn of the key. Idles sweetly.

Tony, thanks. The brakes were overhauled early this year but it feels quite differetnt from the effect of pins not sliding.

No obvious splits in hoses, hoses fallen off.

Session with the local garage booked for Wednesday. The owner is the former area manager for Volvo service and he knows 940s like the back of his hand.

[Laird Scooby]

Originally Posted by martin calva

Dave, thanks. It's diesel. Starts 1st turn of the key. Idles sweetly.

Tony, thanks. The brakes were overhauled early this year but it feels quite differetnt from the effect of pins not sliding.

No obvious splits in hoses, hoses fallen off.

Session with the local garage booked for Wednesday. The owner is the former area manager for Volvo service and he knows 940s like the back of his hand.

I'd look at the vacuum pump if i was you Martin. They don't last forever and failure is often sudden. There is no inlet manifold vacuum developed on a diesel so a separate vac pump is fitted to provide the brake servo with vacuum. Not sure if Volvo have used an electric pump or if they've used an engine driven pump - following the hose from the brake servo will give you the answer to that. If it's electric, check the fuse. In both cases, remove the servo hose from the pump, start the car and check for vacuum on the pump, preferably with a vacuum gauge.

A favourite on Ford Transits from a similar era was to mount the vacuum pump on the back of the alternator, when the vac pump went it leaked oil into the alternator causing failure of that as well. No charge and no assisted brakes!
I don't think Volvo have done that but the vac pump would be my first port of call to investigate.

[classicswede]

Had the same issue with my D24, the servo pipe had gone soft and closed up

[Laird Scooby]

Originally Posted by Laird Scooby

Could also be the hose between the servo and manifold (assuming it's petrol and not diesel) has collapsed internally or the NRV on the servo has failed. Worth checking all of that, split hoses etc too.

Originally Posted by classicswede

Had the same issue with my D24, the servo pipe had gone soft and closed up

Hopefully he's checked it seeing as it's been suggested twice now.

[martin calva]

Last week I booked for the local garage (the owner is an ex Volvo maintenance area manager) to take a look at my brake problem. I had hoped to have diagnosed the problem myself before taking it there but the car was garaged several miles away and I simply ran out of time while working to meet some unrelated deadlines.

The garage owner started the engine with his foot on the brake pedal and said (in French) "Yes, you have a brake problem. It's either the pump or the servo ". He pulled the pipe fitting out of the servo unit, put his finger over the end and said "No suction. La pompe est foutue".

He told me to get a new vacuum pump from Skandix as that would cost me less than he could supply one for. He told me also to get a new tappet, as mixing an old one (500,000 km+) with a new pump is not a good idea. He said it would take them around ½ hour to fit the pump and to give them a call as soon as the parts arrive.

All I need to do now, it seems, is to find what is the engine number for my 2.4 diesel and I'll be able to order the new pump and tappet from Skandix.

My thanks to everyone for all the advice.

[Laird Scooby]

Originally Posted by martin calva

All I need to do now, it seems, is to find what is the engine number for my 2.4 diesel and I'll be able to order the new pump and tappet from Skandix.

My thanks to everyone for all the advice.

According to Pg 4 of :

http://www.myvolvolibrary.info/Tech_...DataPocket.pdf

on yours, the engine type code and number is stamped just below the vacuum pump Martin.

http://www.skandix.de/en/spare-parts...ke-system/543/

Vac pumps to choose from ^^^^^ and two different sorts of tappet :

http://www.skandix.de/en/spare-parts...ke-system/544/

Again, engine number dependent, that said the early (pre-94) tappet is discontinued.