VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit

Honest John Back Room » Technical matters
View Threaded
Sun 10 Aug 2014 16:51
VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit - KenC

Hello HJ readers, I am hoping someone can give me some advise please.

I have lost my trusted independant mechanic and about to arrange a fluid service on my 11 year old Golf

( that I have owned from new).

I know the clutch & brake hydraulics share a common master cylinder.

I obviously want the brake & clutch fluid changed correctly,( not just the brakes bled) however I have concerns about the bleed order of the wheels.

I also would like to know is there any value in changing the hydraulic steering fluid ? the workshop manual indicates just to check the level when cold at a certain mileage.

Having studied my workshop manual it appears that there are two types of hydraulic modules one type (mark 20IE) states start bleeding at the rear wheels, the second type (mark 60) states start bleeding at the front wheels.

I do not want to end up with a messed up ABS module ( I believe they are expensive)

Should I go to VW and pay their extortionate price or would an independant garage know enough get it right first time.?.

I have photographed what I believe is the module, it is 1JO 614517J

my key questions are

1. is it necesssary to change the power steering fluid ? ( it is original)

2. should the clutch be bled first, then the brakes ?

3. how can I establish the bleeding order for the wheels so I can at least ask an independant what bled order he would choose ?

4. does the use of a professional brake bleeding machine negate the occurance of any problems ? eg the bleed order is irrelevant

ps I believe the VW main dealer price for brake fluid change is £60 but I am unclear whether or not this also includes bleeding off the old fluid in the clutch.

Edited by KenC on 10/08/2014 at 16:53

Reply | Report as offensive | Link
Sun 10 Aug 2014 20:53
VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit - elekie&a/c doctor
If the pas is ok and the fluid is a good colour ,I would leave it alone.Any good Indy garage will know the correct procedure for brake fluid change and most use some form of power bleeder so that the master cylinder is not taken to extreme travel.Usually start with the rear brakes,as they are furthest away from m/cylinder.I don,t think anyone will bleed the clutch hydraulics unless you specifically ask.If the clutch action is ok,then again,leave it alone.
Reply | Report as offensive | Link
Mon 11 Aug 2014 09:15
VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit - Railroad.
I agree with the above. In theory it's a good idea to change brake fluid, but in practice the procedure can often create more problems than it solves. I find the best way is to use an Easy Bleed tool, which applies a small amount of pressure at the reservoir and continuosly replenishes it with new fluid. You then open each bleed nipple in turn until the fluid runs clean and you are satisfied the old fluid is out if the system. With this method the master cylinder doesn't move and one person can do the job easily and completely.
Reply | Report as offensive | Link
Tue 12 Aug 2014 08:52
VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit - The-Mechanic

As has been said, if the PAS is working OK and the fluid is in clean condition, leave it alone. There's no real benefit in changing it and to do so involves removing a pipe or union on the rack which in turn will make a mess.

With the brake fluid, I use a vacuum bleeder kit and start at the furthest brake from the master cylinder (passenger side rear in your case) and work my way to drivers rear, passenger front and lastly, drivers front. Using a vacuum bleeder, I find lessens the chances of master cylinder seal damage as there's no pressure acting on the cylinder that could reverse any of the seals.

The clutch fluid, even though it shares the brake reservoir, isn't as critical to change as it is rarely subjected to the same pressures or heat that the brakes do. Of course, the fluid can still absorb moisture from the atmosphere and there is the slight possibility of cross contamination where a small amount of fluid that's retuned to the reservoir from the brakes gets into the clutch line.

Bleeding the clutch with the vaccum kit is no different than the brakes apart from you having to gain access to the bleed nipple which usually involves removing the air filter housing and/or battery.

Your concerns of damaging the ABS module by changing the fluid are very slim. If you've read the horror stories of the ABS module failiures, don't worry. The effected modules suffered from the brake pressure sensor and changing the fluid will have no effect on it. Plus it was only the MK60 Teves units that were effected by the sensor failiure so if yours has the alternative type, you have no worries at all.

Edited by The-Mechanic on 12/08/2014 at 09:00

Reply | Report as offensive | Link
Fri 15 Aug 2014 12:43
VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit - KenC

Thank You All for your very enlightening replies, certainly it has given me something to

think about.

I wonder is there any easy way to find out if I have the MK60 Teves Mudule fitted ?

I believe my car was one later productions of the Mk4 Type before it was replaced by the MK5.

Reply | Report as offensive | Link
Tue 12 Aug 2014 13:47
VW GOLF MK4 2003 pd 130. engine code ASZ - Brake ABS Hydraulic Unit - Cyd

If you are using a pressure or vacuum system to bleed the brakes this should not cause any concern. I'm not personally convinced that the bleed order is critical either as long as plenty of fresh fluid is bled through. Of couse, if you know th emanufacturers recommended orde then follow it.

The two things to watch are:

# DO NOT push fluid backwards through the ABS module (eg when pushing pistons back)

# DO NOT apply too much pressure with a pressure bleeding kit (up to about 30psi is safe generally)

Any skilled mechanic will know these things.

Reply | Report as offensive | Link

Looking for a garage you can trust? Honest John's Good Garage Guide has thousands of reader recommended garages, plus how-to guides and tips on servicing.

The Good Garage Guide