Help - Trying to replace hydraulic roof pump reservoir

Newbie Joined: Jul 16, 2010 Posts: 3

Hi - ive just bought a '94 cab and it has roof problems (which I knew about when I bought it). Ive replaced drivers side boot wiring loom which had some broken wires and now I need to sort out the hydraulic pump. On inspecting it I found it low on fluid and found fluid in the spare tyre well, so it obviously has a leak. Feeling the reservoir its obvious that it is not attached firmly to the pump itself. How is the reservoir fixed to the pump? ive read in different accounts that it is either screwed to the pump, bolted to the pump or attached by some plastic lugs - does anyone know which it is please? I am buying a replacement reservoir and plan to fit it. Am I right in thinking that this is not possible to do with the pump still in the car? If I have to remove the pump to replace the reservoir will I have to move the petrol tank as one account that i have read suggests or has anyone managed to do it without moving the petrol tank? Grateful for any suggestions.

Posted: Mon Aug 16, 2010 8:05 am

Welcome to the site; hopefully one of the more knowledgeable owners will reply soon.. (not got one, so I can't help you)

Posted: Mon Aug 16, 2010 11:32 am

Hi, there's a guy on e-bay who sells them for about £20. If you search for "Audi hydraulic reservoir", you'll see what it looks like. From memory, I think it has 2 or 3 screws and a rubber seal.

Posted: Mon Aug 16, 2010 11:54 am

I've not done the job myself but others on here have, the info on here suggests that 2 screws are accessible but the third requires access only if the fuel tank is released from it's mountings and shuffled out of the way.
It will be an in-situ repair due to all the hydraulic and wire connections going to the pump. The posts in the archive should point to more info.

Newbie Joined: Jul 16, 2010 Posts: 3

Thanks guys thats very helpful. I am operating the hood manually at the moment and to be honest I'm finding its quite quick and easy. But I will have a go at the repairr as soon as I get the time. Thanks again

Posted: Mon Aug 23, 2010 7:52 pm

I thought I had a leak as well. Was in fact a slight drip from a hydraulic piston. Caused a hell of a mess. Must have been leaking for years.

Thought the fluid was low but discovered the level changes depending on if the roofs up or down. The level needs to be checked when the roofs down or else you over fill.

Posted: Mon Aug 30, 2010 5:21 am

I ve still got my old faulty pump in the garage if you would like to take a closer look at one before tackling your own. Not sure where you are.
Sniff

Newbie Joined: Jan 12, 2010 Posts: 1

I replaced the reservoir in my 1996 Cab (USA) recently. The reservoir had a crack on the bottom and had leaked dry. I bought the car that way. The relay was also burned and melted. Probably from repeated attempts to operate the top.

I had to remove the pump to get at the 4 machine screws. The pump is mounted with 2 pivots, one front and one back. The rear pivot is a stud with nut that can be accessed from outside below the bumper. There's a rubber plug covering the access hole. The front pivot can be accessed from the inside of the trunk with difficulty. I removed the spare tire and everything else including the liner. By squeezing my hand into the hole in the bodywork and using a closed end geared wrench, I was able to remove the nut from the front pivot. The pump can then be raised at the rear and to the rear such that the front pivot pulls out of its mount. The pump is very heavy so be careful. I didn't remove any of the hydraulic hoses. That would be a bad idea.

The new reservoir should come with a new o-ring seal and 4 new screws. Pull the old reservoir off. Put the new o-ring on the reservoir and wet it with hydraulic fluid. Slide it onto the pump. It's difficult. Just work at it. Tighten the screws but not a lot. Don't want to crack the new plastic.

Hydraulic fluid - I noticed that the specified fluid is the same as the power steering fluid. I used Pentosin 11S.

Now to fill the reservoir. I was not successful using the top fill port. It just wouldn't take much fluid before overflowing. So I used the side port, left side of the pump. It goes directly into the reservoir. A small long neck funnel comes in very handy.

I had to fill and then operate the top to get the fluid to circulate thus emptying the reservoir again. It might not be necessary but I slid the pump back into its pivots when operating the top. Then take it out again and fill the reservoir. It took 4 cycles of this to fill to the max line. Each time I operated the top, it would move a little further until it finally worked normally.

Reassembly is the reverse of disassembly.

I hope this helps you. Good luck.

Bob.

Newbie Joined: Jul 16, 2010 Posts: 3

Firstly, sorry i didnt reply sooner - i was away on holiday.
Thanks for the detailed description of the job - its made me realise that it may be too much for me to take on alone with my limited auto repair skills
. i'll try to enlist some help when I attempt it. I have the repair kit now and will go ahead when I can. Thanks again for the replies.