Air leak releasing brake pedal no boost 1.9 tdi 150 please help

Hi.

I have a 2002 1.9 tdi golf 150 bhp pd.


I have an issue which I believe in my optimism could be relatively simple with correct knowledge of these cars as they are quite old and understood now by many , unfortunately not by me in this instance.*

My issue is on releasing the brake pedal there is a hiss noise which sounds like air escaping the breaks work fine .

All information oline is about constant hissing which stops when brake is pressed and brake pedals going hard .

The car does neither , only a hiss which occurs as the pedal returns to it's natural position which sounds like air escaping. The opposite of brake hissing related noises the internet is adorned with.

The vehicle is also down on power , turbo is not boosting .

It appears to have no obvious vacuum.leaks and from hours of reading things like ,servo brake booster hiss constantly when failing brake pedals go hard etc .
I just have no turbo and a hiss as the pedal returns to its natural position after braking*
.

So I'm at a loss .. if anyone has any knowledge of this issue a hiss on releasing pedal and could explain if it could be linked to lack of turbo boost and vehicle running with reduced power .

You really would be helping me thanks in advance

If it were me I would get a vacuum gauge and see if the vac pump has gone south or if the hose(s) have developed a leak. I would suggest disconnecting everything from the vac system and checking the vac pump by itself; at idle a vacuum of 20-25" would be optimum. If you have solid vacuum then start adding back one thing at a time to find out where the leak/problem is. Just a thought...every solenoid in the vacuum system has the potential to be cracked and adding to the vacuum loss causing your current problem. I hope this is of help to you.

Gone south haha thanks sound advice , theres an oil leak from
Around the pump, I can get a second hand one for 50 pound.
ARL mk4 golf 150 they dont seem specific .
They seem to be same pump.on loads of variants..so will try this first ,
I feel I maybe ok with a second hand one because from reading on here they dont fail all that often , vw in uk want over 300 for the real deal so will try this , as its flat as a witches tit at the moment no boost anywhere ,
My other thought was the booster but I'm.not sure I have the symptoms of a failing booster , thanks again for your advice it's a plan of action at least regards

Do the brakes work when you get into it, it are they flat. If they're flat then the booster is likely shot. Barring a vacuum leak somewhere else.
Follow above and go through it hose by hose. If no other leaks present booster or other component is leaking.

It's a tandem pump on the PD (PUMP DUSE) so the vacuum pump is the high pressure fuel pump. It needs to be from a 1.9 PD engine...

Sent from my moto g(7) power using Tapatalk

Thanks , the pedal is fine it has abit of travel before the brakes work ..but the pedal is not to the floor in anyway ,or hard to press..everything is fine no hissing when running etc

Only symptom is brakes are a little weaker than you would expect given as the brakes disc and pads are new.
Just after you have braked the pedal hisses on it's way back up .

The part number for the tandem pump I got from vw
It is

038145209q

Notice is has a q at the end
.now on ebay there are loads of vacuum pumps with this part number but although the numbers are the same they all have different letters at the end for example
038145209N and pretty much every letter of the alphabet .
Is it essential i find one with the letter q at the end or are they all alike
Mk4 golf 2002 pd 150

Thanks for all your help I was really at a loss this afternoon.with this , seem to getting there now. Much respect

Probably not. Ebay is not a great source. VW updates part no. like that all the time, so older stock might carry different suffixes. If you're looking to save money, there are rebuild kits available.

I'd rebuild before buying used.
The suffix Q is the latest version of that's the number VW have you recently.
They updated the part number alphabetically and a-z the last letter is newest rendition.

Sent from my moto g(7) power using Tapatalk

BobnOH said:

Probably not. Ebay is not a great source. VW updates part no. like that all the time, so older stock might carry different suffixes. If you're looking to save money, there are rebuild kits available.

Click to expand...

I like eBay personally!
I find OEM parts listed by stealerships all the time.
If I can wait I'll go that route...

Sent from my moto g(7) power using Tapatalk

eddieleephd said:

I like eBay personally!
I find OEM parts listed by stealerships all the time.
If I can wait I'll go that route...

Sent from my moto g(7) power using Tapatalk

Click to expand...

eBay can be great for finding OEM parts cheap via part number searches.

If also say check vac pump with a Mighty Vac or similar.
No turbo or brakes sounds like a full system issue likely related to a bad pump.

They do wear out. Mine did. Wasn't a sealing issue either as seals were new

Isn't it supposed to do that?
Hissing from around the brake peddle.
That's where you are hearing it right?
The vacuum has to go somewhere when you release the peddle and the booster goes back to the normal state.

Maybe, thanks for the advice , what you say makes sense, I just cant think of ever noticing a noticeable hiss from a pedal before ,not just on this golf but on many cars it's quite loud.

Would all this be enough to remove all boost ,
The car does not feel in limp.mode (as cars usually go very very slow in limp mode)
Speed is not limited ...
But it feels like it has about 90bhp as instead of the stock 150bhp it has.
And there is no boost you can feel .

The vacuum pump seems a good start ..
Its 30 pound plus a new gasket
So worth a go .....

All this happened after a garage change the fuel filter has issues starting it , and was hard to start 50 per cent of time since weak start

It may be unconnected but the timing seems abit close.
I'm going to work on it myself from now on , not just to save money but to avoid any more potential problems

I'm gonna plug it in., see if I got any codes , as all the vacuum lines look ok,
If there was a vacuum.hose causing this much lack of power would it be fairly easy to spot , In your experience

Sounds like when the garage replaced your filter they didn’t replace with new or didn’t get the O rings back on correctly and now you have an air leak into the fuel line. Does your car start harder after it sets overnight? Or is the hard start just random?

I’ve never noticed hissing in my PD when I let off the brake pedal.

Since the garage was working over by your boost pipe, make sure the pipes are firmly attached and not cocked at an angle. Here in the states the PD’s have that clip system and it wears out and allows pressure to escape. Maybe the hiss you hear is a boost pipe jiggled loose by an incompetent garage mechanic.

Definitely worst in the morning!!
Does it mean something it's ok in the day thanks bro

You have air getting in your fuel lines overnight, that’s why it starts harder in the morning. The most likely entry point is the T on top of the fuel filter. The air leaks in all night so it starts hard in the morning. It’s a small leak so it doesn’t cause hard starting if you shut it off and restart fairly soon.


Check your boost pipes for an air leak also which would be the cause of the hiss, your hearing.