VW Polo 2000 – no brakes after brake job

[Jacob Andersen]

Car in Question:
VW Polo 1.4 16V (55kw/75bhp) – year 2000
Motor: AHW/AUA/APE
Transmission: DUY/085 5-speed manual
VIN: WVWZZZ6NZYY56xxxx
125.000 km/80.000 miles on the clock

No service light alarms.

Question:
I replaced all wheels with new brake discs and brake pads and have overhauled all four calipers (Lucas 54 front and Lucas 34 rear) with new slide pins and rubber seals.

Unfortunately the master cylinder was allowed to get empty during the proces.

I therefore replaced the brake fluid and bled all four wheels with the “old” brake pedal maneuvre.

The master cylinder is now full and stays full with no apparent leaks.

When i started the car it had problems starting, but quickly started, but the brake pedal went straight to the floor. The car idles OK now. It is possible to build up some brake pedal by pumping the pedal real fast, but when i then try to activate the semi-hard brake pedal it goes to the floor and the car sounds like it is going to stall, but then idles normal again.

There does not seem to be any air in the lines as I have bled all four wheels again today.

Has the master cylinder internal seals been damaged or gunk’ed up because of the brake pedal maneuvre?

Is it air in the ABS-pump? The Haynes manual does not state any particular actions to the ABS-system when you have replaced the master cylinder besides bleeding the entire system.

Should/Could I try something before replacing the master cylinder.

MODIFY
No, I did not bench bleed or bleed the master cylinder. I “just” refilled it several times, making sure that it did not get empty again, and then bled out approx. 500 ml (5 cups) old and then new brake fluid from each caliper.

Could I isolate the problem to the master cylinder by clamping off the flexible brake hoses at each of the wheels to “take away” any matters regarding the calipers? I just want to maybe get a little more evidence before I just replace the master cylinder. This is what i expect they will do at the auto shop.

Topic

[mckrishes]

Since the master cylinder went dry, you have air in the abs chamber. You need a scan tool to connect to the computer so the abs motor can be activated while bleeding the system. However I would re-check all of your work and make sure all hoses, vacuum lines, etc. are properly installed. You can buy the tool at the local parts store or take it to the local shop and have them do it for you.

[college man]

you could try this bleeding procedure.LF RR RF LR
if the fluid comes out solid no air.then you may
need a scan tool to open the abs solenoids.

[EricTheCarGuy]

I suppose it could be a couple of things. The first thing that came to mind was that you might have a bad master cylinder especially if you didn’t crack the bleeder valves when compressing the pistons on the calipers, I have seen this practice damage master cylinders in the past. If that’s the case then I think your test might work to determine that however if your vehicle DOES require that you reset the ABS with a scan tool this could also be the cause. At the end of the day you may be looking at replacing the master cylinder and if that doesn’t work explore the ABS reset option. Before you spend money on a new master however you might want to look into if you need to perform a reset procedure for the ABS or not.

[Jacob Andersen]

Hi. Thanks for the responses so far.

The pistons in the calipers were compressed “on the bench” and then put back to the car.

Looking around on the internet I have gathered the following information.

Possible causes:

– master cylinder internal seals damaged because of “old” pedal brake bleeding method – theory is that the greater than normal travel of the internal seals when using this brake bleeding method will force the seals out in a not normally used part of the master cylinder filled with corrosion and dirt – which distorts the seals and thus leaking.
– air in ABS pump (not sure if this is a problem with my particular car model) – bleeding the ABS part of the system normally requires some expensive dealership hard-/software (VAG-COM) so that one can turn on the ABS pump and thus bleeding the air (and the old brake fluid) from the ABS system out to the non-ABS system – from where it should be bled by one of the ordinary bleeding methods.
– trapped air in 1 to 4 of the calipers as i forgot (I have spanked myself…) to fill the calipers with brake fluid before they were put back on the car – so that air is (could be = is in car world accordind to Murphy’s law) trapped in the top of the calipers.

I have just received an “new” used master cylinder (which could be or could not be working out of the box…!).

Diagnostic approach:

1) Isolate master cylinder by clogging off the outlet ports with M10 bolts > firm brake pedal > master cylinder is not the cause. Otherwise replace and continue approach.
2) Isolate brake lines from master cylinder to brake calipers by squeezing of all four of the flexible brake hoses with double clamping (you f….. need to be sure that they are squeezed off to use this as a diagnostic approach) > firm brake pedal > brake lines are not the cause. Otherwise look along brake lines to find leakage (park on dry surface over night with heavy stone on brake pedal to create pressure in system).
3) Un-squeeze one flexible brake hose one at the time to find the brake caliper(s) which are creating the menace. The look for leaks in the caliper. Take off the caliper while still attached to the brake hose – then rotate the caliper and have the bleeder nipple at the highest point when rebleeding.

This should be fun (NOT!). Will keep you posted in some days.

[Jacob Andersen]

So today was certainly a loooooong day.

I now have brakes – hurray!

PROBLEM turned out to be – external leakage and possibly trapped air.

Double clamped all four flexible brake hoses. Hard brake pedal.

Master cylinder – OK.

Brake lines – OK.

Took off all four calipers and then injected them with new brake fluid while tapping and turning them, with the bleeder screw up, to get out all trapped air pockets.

Put the calipers back but still had a somewhat harder but still sinking pedal.

Found a tiny leakage from front left brake hose bolt. Turned out to be due to a missing brass washer (there should be one above and one below the brake hose inlet thingy – :pinch: ).

Fixed that. Ready to go. One final round to torque up all bolts and screws.

F………………….! Sorcery is in play. Rear right bleeder screw was suddenly loose. I don’t know how, but I somehow managed to screw up the thread :whistle: . Then off with the caliper again again. As the car uses M10 bleeder screws I had to cut a new M12 thread down into the old thread, put in a little steel ball, and then press the steel ball down into the bleeder port hole with a giant M12 bolt (I only had like 2″ long ones). But it somehow did the trick and I will quite surely not see any leakage from that port in the future (but will have to bleed through the brake hose bolt – inlet port).

I then finally managed to get a somewhat firm (maybe a little spongy) but non sinking brake pedal.
Then took the car for a progressively tough drive in the mountains and turned ON “poor man’s VAG-COM” – activating the ABS pump by making some tough braking maneuvers letting the ABS kick in. When I got home the brake pedal was a lot more spongy – so either I succeeded in getting some of the possible air in the ABS system out in the brake circuit, or else something else is wrong.

Will look for leaks tomorrow and then do a final bleed.

[dreamer2355]

Good job thus far and keep us posted!

[Jacob Andersen]

UPDATE.

Checked the car this morning. No fluid inside rims or on the ground.

Then re-bled all four wheels – RR>LR>RF>LF. Bleeding the final wheel (left front) I was a little stunned to see some 5 inches of real dirty brake fluid pass through the tubing – maybe some of the old brake fluid from the ABS system? If that is the case, then “poor man’s VAG-COM” seems to have been working all right.

I now have brakes, one closed up for good brake bleeder screw at rear right caliper, but unfortunately with a little to much pedal free play.

At this time I do not have the time or the energy to try reducing the pedal free play.

But I hope it will pass the MOT-test tomorrow morning.

CONCLUSION

All ways make sure to make a thorough job as you work your way around the car. You should be able to “trust” what you have all ready done, as to rule out possible causes, but if in doubt or encountering problems, then go back to start and work your way through all of your work one more time.

A missing 50 cent brass washer can some times “destroy” your brakes and make you or your mechanic buy you a new master cylinder and possible buy you one or more new brake calipers (none of which would have dealt with the problem).

Keep you updated on the internet. The information you need is out there but you have to put together all the bits of information from several places.

If in doubt – one should probably take the car to a “real” mechanic – one of those who actually diagnose car problems and repair cars. Not one of those who “just” replace parts until the problem is fixed.

[spelunkerd]

This is a great story, one not often told on internet forums. It’s a cautionary tale, for those who want to start doing their own maintenance. Sometimes these jobs don’t go according to plan, and you can cause more harm than good when you try to fix things. A huge amount of wasted effort.

Once, after rebuilding the rear caliper on a VW Jetta, I had a soft pedal. My first assumption, inadequate bleeding or a bad MC, was wrong. Turned out I didn’t get the pads close enough to the rotor to allow the automatic adjustment to work properly. I would have thought the piston should have pushed the pads inward until there was contact, but somehow they need something to press against to reset. They were just a little too far apart to do that in one stroke. After pushing the pads together a few mm, the brakes worked perfectly.

Your description of retapping the bleeder screw hole is interesting — I thought bleeder screw threads are tapered NPT threads, and retapping would be a problem. Do you have a functioning bleeder screw now on that caliper?

[Jacob Andersen]

I myself thought it was a failing master cylinder.

I can honestly say that I am happy to have finished this project. But I have learnt so much from this single brake job.

No, I do not have a functioning bleeder screw at rear right wheel. I somehow had to close the port and thus tapped a M12 thread, put down a little 3 mm steel ball to block the port hole, and screwed in a M12 bolt to keep the steel ball tight in there. I bled that wheel through the brake hose inlet port. A little more difficult but doable.

[Jacob Andersen]

Passed MOT-test today without any remarks.

Next project.

Car used to (for like 6 month ago) run like 150 km/t (some 90-95 mph) but will now only do 120 km/t (some 75-80 mph) and seriously lacks power when over taking or driving up-hill.

I have done all the obvious and easy fixes – complete oil change, changed air filter and cleaned throttle body thoroughly, changed fuel filter, changed spark plugs. No white or black smoke from exhaust. No butter cream in cooling fluid. Just passed MOT-test with no emission failures. No “hanging” or locking brakes. No obvious clutch problems but more than anything lacks power in especially 5th gear.

I have by chance a head gasket set with head gasket and valve seals for that particular model and make and think I will try and see what a 1.4 16V DOHC looks like taken apart.

[EricTheCarGuy]

I think you might have answered your own question, give this a try.

[Jacob Andersen]

Hi Eric.

Yes indeed. I my self (and Irene) thought I could be a clutch starting to fail. And your inspiring videos made me think that a clutch project could be “interesting” – mind that I have never done one before.

This car is a budget VW from the era were VW started to cut corners. Not as “bad” as many, and with a good sturdy engine, but is unfortunately known for bad clutch and bad transmission. Especially as this little car is often used as a city car with a lot stop and go.

I guess that you in general will either be tough on your clutch (using down gearing to reduce speed) or be tough on your brakes (easier to fix).

When you are doing the clutch repair – are there any other replacements (drive shafts) you suggest that the customer to have done as you have allready taken like 1/4 of the car a part?

Keep up the good work and pleace keep up the ranting and your personal comments. This is really what makes your videos so “funny” and “inspiring”. Near miss with your finger almost getting crushed between ball joint and lower wish bone…! HeHe. You did get silent there for like 30 seconds.

Stay squirty.

[Jacob Andersen]

Last update.

Everything seems to work fine. Brakes are working and with no apparent leakages. I now have a master cylinder in my inventory which could come in handy some day.

I even replaced the manual transmission gear box with new oil and a car that is known for its bad transmission now have nice and smooth gear shifting.

Will take the car for a 500 mile drive tomorrow.

Thanks for the replies here and else where on the forum – pieces of advice that mada such a huge difference.

[college man]

thanks for the update.

[Author]

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