Polo 9N 1.9TDi Tandem Pump Vacuum Spec

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dhirennaidoo
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Polo 9N 1.9TDi Tandem Pump Vacuum Spec

Post by dhirennaidoo »

Hi guys

Just looking for some input on an issue on my ATD Polo.

1. Does anyone have official specs for testing the vacuum at the tandem pump?

2. At the tandem pump, there is a big vacuum line going to the brake booster, with a small tee piece with line going to port 1 on the "vacuum box" (black box with all the vacuum lines on left of engine bay) Is pulling this pipe off a valid place to plug a vacuum gauge in? I am getting readings of approx 6 inHg / -20 kPa at idle. From what I see on tdiclub, etc, this should be around 20-25 inHg.

3. Took off the vacuum lines at the "vacuum box" to check for leaks with a MityVac.
->Box to EGR - OK
->Box to vacuum reservoir (black ball) - OK
->Box to turbo - OK
->Box to ASV - OK
->Box to tandem pump & brake booster - leak

So, I'm thinking the tandem pump is leaking, or the MityVac can't pull a vacuum fast enough to test the tandem pump, or I'm being daft and the tandem pump shouldn't be tested this way. I should mention that there are no blatantly obvious vacuum issues. Turbo vane response seems fine. ASV closes when switching off.

I suspected this because for about a month now, the brake pedal has been getting hard after a few repeated uses. Sort of like when you switch off and try using the brakes. After revving the engine up a bit, the pedal feel comes back. Discs and pads are fine from what I can see. Bled the fronts. Brake fluid hasn't been changed in about 2 years, but can't see that being an issue all of a sudden.

Thoughts?
Last edited by dhirennaidoo on Wed Mar 06, 2019 6:10 pm, edited 1 time in total.
'08 350Z
'05 Polo Classic TDi (PD100)

Ex : '12 Mk6 GTi Ed35, '91 Fox 1.8, Honda CBR600F, '09 Honda CBX250 Twister
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dhirennaidoo
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Posts: 786
Registered for: 17 years 6 months
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Re: Polo 9N 1.9TDi Tandem Pump Vacuum Spec

Post by dhirennaidoo »

Also, is this elbow at the back of the tandem pump supposed to rotate freely?Image
'08 350Z
'05 Polo Classic TDi (PD100)

Ex : '12 Mk6 GTi Ed35, '91 Fox 1.8, Honda CBR600F, '09 Honda CBX250 Twister
Terblanche
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Re: Polo 9N 1.9TDi Tandem Pump Vacuum Spec

Post by Terblanche »

Good day.
I'm not sure about any specs, but if you cant get a vaccum going then there must be a leak. I dont think it should be rotating freely, I used pratley steel to fix it on my 1.4 tdi and my brake problems went away. It did not fix my underboost errors though.

You can also check the plastic pipe going from the tandem pump to the brake booster, they like to crack as well. I replaced mine with normal 1/2" plastic tubing which I heated and bent to look the same as the old one.
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dhirennaidoo
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Posts: 786
Registered for: 17 years 6 months
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Re: Polo 9N 1.9TDi Tandem Pump Vacuum Spec

Post by dhirennaidoo »


Terblanche wrote:Good day.
I'm not sure about any specs, but if you cant get a vaccum going then there must be a leak. I dont think it should be rotating freely, I used pratley steel to fix it on my 1.4 tdi and my brake problems went away. It did not fix my underboost errors though.

You can also check the plastic pipe going from the tandem pump to the brake booster, they like to crack as well. I replaced mine with normal 1/2" plastic tubing which I heated and bent to look the same as the old one.
Thanks, Terblanche. Will check the main line from tandem pump to brake booster, haven't actually checked it like I did the smaller ones.
'08 350Z
'05 Polo Classic TDi (PD100)

Ex : '12 Mk6 GTi Ed35, '91 Fox 1.8, Honda CBR600F, '09 Honda CBX250 Twister
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dhirennaidoo
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Posts: 786
Registered for: 17 years 6 months
Car Make: VW
Car Model: 9n Polo Classic TDi (PD100)
Membership No: missing
Location: Johannesburg

Re: Polo 9N 1.9TDi Tandem Pump Vacuum Spec

Post by dhirennaidoo »

Terblanche, I owe you a beer :D

That pipe was split right at the tee/ non-return valve. It's not in stock anywhere, so taped it up temporarily until the new pipe arrives but at least my brakes are back. Thanks!
'08 350Z
'05 Polo Classic TDi (PD100)

Ex : '12 Mk6 GTi Ed35, '91 Fox 1.8, Honda CBR600F, '09 Honda CBX250 Twister
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