Xantia TD Vacuum

swiss_steve · Unread post by **swiss_steve** » 11 Aug 2010, 19:21

Hi all,

I would be grateful for some help and guidance on this new problem of mine....

For some unknown reason, the vacuum on my engine just suddenly stopped working whilst on a trip. How do I know this - because it also feeds the cruise control servo that I installed years ago.

Upon checking things over, no obvious signs of problems - no split or perished hoses, no major oil leaks around the vauum pump, but definitely no vacuum. There is also no movement on the fuel pump fast idle control diaphragm (which until now has always moved according to accelerator/throttle position).

Are these vacuum pumps liable to failure? If I need to change one, how can it be done (the Haynes BOL is useless)? Should I check the two pneumo-valves (attached to the engine compartment bulkhead), and if so, how?

Sorry for all the questions, but I'm a bit stumped on this one...

Cheers,

Steve

f00lzz · Unread post by **f00lzz** » 11 Aug 2010, 19:27

That's a new one on me Steve.. where is it located?

swiss_steve · Unread post by **swiss_steve** » 11 Aug 2010, 19:43

Nearside end of OHC (the vacuum pump - visible under the breather hose - is surely connected to the OHC shaft).

Just to the right of the photo you can just see the hoses that all go to the LHM Tank....

Xaccers · Unread post by **Xaccers** » 11 Aug 2010, 19:49

the two electrovalves control the EGR and fast idle, they can fail.

find the feed pipe from the vacuum pump on the end of the engine and disconnect that, then with the engine running check for a vacuum from the pump

Kowalski · Unread post by **Kowalski** » 11 Aug 2010, 20:30

If you suspect your vacuum pump to be faulty you need to verify it first. The simple way to do this is to attach a vacuum gauge directly to the pump on its own. If you don't have a vacuum gauge, you can try sticking your finger over the inlet / outlet to assess how much vacuum it is producing, once you've got that ruled out you can look at the rest of the system.

The vacuum hose that goes from the eletrovalve to the EGR valve gets affected by heat, hardens and will split where it goes onto the EGR valve, this is well hidden down the back of the engine. When it splits like that, it vents vacuum to atmosphere and you can end up with no vacuum.

Its not unheard of for vacuum diaphragms to get holes in them and you to lose your vacuum that way too.

swiss_steve · Unread post by **swiss_steve** » 12 Aug 2010, 11:23

Hi again everyone,

With daylight again, I've now checked the hose coming directly off the vacuum pump and there's plenty of suck on that baby!

Next to check are the electro-valves. I assume as they are simply a 12v solenoid - that putting some power into the terminals should result in a noticeable 'clunk' or similar, to give an indication of operation. Are these parts still available from Citroen? Anyone know what the part no. might be, please?

P.S. As it happens (more by luck than judgement), I tapped in my vacuum cruise servo to the hose downline from the fast-idle control diaphragm, so it is possible the EGR valve is functioning normally (haven't noticed any turbo problems or change in characteristics - but then I don't boot my elderly carriage....).

Cheers,

Steve

Xaccers · Unread post by **Xaccers** » 12 Aug 2010, 11:32

I'd take the cruise vacuum from the pump before the electrovalves rather than after if you just need a vacuum.

If your engine idles at around the 1000rpm mark, then your fast idle electrovalve is duff. No real problem running like that, it just stops the engine idling at the 850rpm mark (no vac=fast idle).
If your egr electrovavle is working, disconnect the pipe from the valve to the EGR and bung it up to disable the EGR.
I love the description of an EGR being likened to farting up your own nose

swiss_steve · Unread post by **swiss_steve** » 12 Aug 2010, 11:44

Hi Xac,

Yes, you're right, it does idle at 1,050 rpm. So now I'm happy that it's not causing any engine damage and can get a new valve from the Dealer in due time.

However, I note you are you suggesting I plug the EGR vacuum hose - why is that? Surely Citroen wouldn't put the feature in unless there was good reason? I don't get any problems or farting noises....

Xaccers · Unread post by **Xaccers** » 12 Aug 2010, 12:20

It recurculates the exhaust gas, to reduce NOx emissions, but in the UK on a diesel that isn't checked.
Basically imagine pumping exhaust gas into the air intake, with all the soot etc. Not a pleasant thought is it?
Disabling it increases the NOx emissions, but reduces the particulate, CO and CO2 emissions, and gives a bit of a power boost.

Unread post by **KennyW** » 12 Aug 2010, 14:50

Hi Swiss Steve,

FYI, here are the prices for the 2 solenoids at the bulk head from citroen services.

Idling Actuator Citroen No 1628L9 £16.92 inc VAT
EGR electrovalve Citroen No 1628CH £25.43 " "

Kenny

swiss_steve · Unread post by **swiss_steve** » 12 Aug 2010, 19:44

Cheers Kenny,

My local Stealership gave me the attached sketch, and price of £14.54 +vat for No. 20.

I guess that does it.

Thanks all,

Steve

Kowalski · Unread post by **Kowalski** » 12 Aug 2010, 23:19

The hose that I mentioned that gets hardened with heat is number 8 in that diagram, number 1 is the EGR valve...

swiss_steve · Unread post by **swiss_steve** » 13 Aug 2010, 09:06

Hi Kowalski,

I'll take another close look at the integrity of all the vacuum hoses this weekend, when I have a bit more time.

Judging by many Posts I have seen on this and other forums, it is best to disable the EGR by plugging the hose (so it remains closed), because it goo's up the Inlet manifold....

Cheers,

Steve