Brakes don't work in reverse

I'm new to the forum and just purchased my first diesel Jetta. Little problems right off the bat but I guess it comes with the territory.

So here is the funny little issue that I've got on my 2005 TDI. When I first start the car, release the parking brake and reverse, the breaks barely work at all. The feeling in the brake pedal is exactly like putting on the breaks while the car is not running. The pedal is VERY firm and gets stiffer with less travel if I pump it (while still rolling backwards). The problem does not exist if go forward first.

I just purchased the car with 150k miles on it and it has the manual transmission. Front and rear pads and rotors were replaced less than a year ago by the previous owner. Any input on this crazy little problem would be much appreciated!

I am guessing that when you go forward, you (as most people do) go faster than when you reverse. This may mean higher engine rpm and more vacuum.

I am guessing you have a vacuum leak. If the 2005 is similar to the 99.5-2003s, there is a large vacuum line from the vacuum pump to the brake booster. Ours tend to develope cracks.

Try starting the car, but reving the engine for a bit before then letting it idle and shifting into reverse, see if that changes anything. Your symptoms of the super firm pedal with little actual brake response sounds like low vacuum.

Even though it only happens in reverse (which is weird), it sounds like you might be loosing vacuum in your brake booster after the car has been shut off.

For an easy test of this theory, the next time you start the car, wait 1 minute before you move. If it is in fact loosing vacuum, that one minute of the car running will give it a chance to build vacuum. If after the one minute wait, the brakes work fine, then start looking for a vacuum leak either at the brake booster itself or the vacuum line going to it.

Hey - worth a try and doesn't cost anything.......

Edit to add - posted at the same time as chromeBuddha - looks like we think the same!

thanks for the input. I'll give that a shot in the morning!

A hard pedal is generally a sign of lack of vacuum at the brake booster.

Since the brake pedal is hard only in reverse, I'll guess that you have a crack in the hose that goes from the vacuum pump to the brake booster. What is happening is that when you reverse the engine rotates forward a bit, that pulls on the hose, opens up the crack. That means no vacuum gets to the booster and the pedal gets stiff.
When you move forward, the engine rotates backwards a bit and this doesn't stress the hose and so the brakes feel normal.

The hose in question is about 1" in diameter and goes from the brake booster to the vacuum pump. It is hard plastic tubing with a ruuber hose where is connects to the pump. Carefully inspect that hose for damage. They can crack on the underside where it's hard to see, so you may want to remove the hose first so you can examine it closely.

vacuum is no doubt the problem. with a few rpms just after starting the brakes work fine. I'll have to get in there tomorrow and inspect the line. thanks for the advice and i will post an update.

That hose was a problem for my braking. We glued it up but eventually got a uncracked used one.

Another area of vacuum leak that affected my brakes similarly to yours is right at the vacuum pump port. It was poorly designed at the outlet so that the outlet post that you clamp to would spin loose inside the vacuum pump.

VW may have corrected that on newer models. However, I just experienced it on mine after having it in for timing belt replacement. Still working out all the bugs they put in it!

This could also be a problem with the ABS. it might think a wheel is locking up when the car is moving backwards.

-J

Thanks all of you for your help. It was the hose that runs from the check valve to the firewall. It is cracked right where it fits over the nipple at the check valve. A little electrical tape and a hose clamp and the problem is solved! Seriously, I will be ordering the correct part. Thanks again for the input!

I love this forum so much. I am having the same problem, sensation of no-vacuum-assist only in reverse (and sometimes for the first braking event after reverse, usually immediately after like when parallel parking). I googled "TDI MkIV reverse brake vacuum" and got this thread as my #1 hit. What a win. I will work on this hose and report back on results!

Took a look at this today, the hose at the nipple to the vacuum pump was able to spin on the nipple somewhat - and this is on top of the previously mentioned nipple design which allows it to rotate in its seat.

I took the hose off the nipple and it appeared intact. The rest of the vacuum lines also appear intact. I got rid of that impossible hose clamp and put on a good old screw driven auto parts store replacement. There has been quite an improvement, time will tell.

Just bought an 04 TDI, same exact issue with brakes being heavy in reverse only (fine while driving forwards).

This forum has been awesome so far!

Will hunt down vacuum leaks tomorrow. Cheers!

Sounds like this problem shows up not because it is a reverse-only problem but rather a brake right after moving problem. When starting moving forward, it is much less likely that the driver will immediately be on the brake pedal, while in reverse, that is highly likely.

Interesting that the reverse only is the description that is being picked up.

Good luck finding the leak(s). It can sometimes be difficult finding leaky vacuum hoses.

Cheers,

PH

Check the hard "hose" near and at the booster. These have been known to crack and when they flex the wrong way they leak enough to cause exactly this sort of symptom.

The other high-risk place you already looked at, which is the nipple on the vacuum pump.

Todd already noted this up above; I've seen it a couple of times on friends' cars....

Thanks everyone in this thread for the help. Really useful as I found a leaking vacuum hose.

vw mk4 braking poor in reverse - sometimes

thanks much for your thoughts. I'd hit the same issue on my 2005 mk4 tdi and finally got under the hood and hunted for cracks, etc. I opted to replace the factory clamp on the pump end of the line to the booster. After tightening the clamp well I found it still seemed loose. Closer inspection revealed that the nipple/outlet as the hose connects to is a separate part of the pump housing as is press fitted in. Mine allowed for rocking slightly and similar to the cracked hose, the shift in engine by reverse motion would, sometimes, allow vacuum loss. High temp silicone gasket sealant and a rubber washer added in between the end of the hose and the pump housing has cured the issue for me. I'll be inspecting the sealant from time to time.

vtdasher said:

thanks much for your thoughts. I'd hit the same issue on my 2005 mk4 tdi and finally got under the hood and hunted for cracks, etc. I opted to replace the factory clamp on the pump end of the line to the booster. After tightening the clamp well I found it still seemed loose. Closer inspection revealed that the nipple/outlet as the hose connects to is a separate part of the pump housing as is press fitted in. Mine allowed for rocking slightly and similar to the cracked hose, the shift in engine by reverse motion would, sometimes, allow vacuum loss. High temp silicone gasket sealant and a rubber washer added in between the end of the hose and the pump housing has cured the issue for me. I'll be inspecting the sealant from time to time.

Click to expand...

Use JB Weld next time when that silicone starts to leak.