MatraSport Forum

Hi.
I seem to have an air leak from somewhere. When I remove the inlet pipe of the white, plastic headlight thingy under the bonnet and connect a vacuum gauge to it, it starts at 15 whatevers on my vacuum gauge and slowly, over the next 10 minutes or so, goes down to almost nothing.

I have replaced the joining rubbers on that end of the pipe and checked and used jubillee clips on all the other rubber joints of the headlamp plumbing system, in the engine compartment. I replaced the rubbers that connect the pipes to the inlet manifold and secured them with jubilee clips too. I also removed the air reservoir and checked that for cracks and it seemed OK.

So my question is, where else should I check for vacuum escaping from my headlight plumbing system? Since I did all that, the car runs better, but the system clearly isn't 100% tight.

Any help gratefully received.

Cheers,

Antony

On my old silver 2,2 the problem was in the white switch which is under front bonnet. The headlamps went closed sometimes when I drove in the night - very funny  :o and sometimes it was jamming and I could hear that air is leaving from it, after I changed it, everything was O.K.

It could be the white one-way-valve in the engine compartment on the T-piece connected to the reservoir and the pipe to the front of the car. It could also be the pipe running under the car. Or it could be a very small crack in the vacuum reservoir.

That's just what springs to my mind. There aren't that many possibilities, really ;)

Is the pipe from the reservoir to the front of the car all one piece?

The reservoir itself looked good, but I couldn't be sure.

Is the one-way valve serviceable at all? I will try and whip it off this week for a look.

Thanks for your help.

Yes it is.
 

No it can't be serviced. It appears to be a standard item normally used on brake servo's.

- Anders 8)

The one-way valve is my current favourite culprit, so I have ordered one from Will.

I hope this solves the problem!

Cheers,

Antony

Mine too... so I'm not going to bet against you this time ;o)

Nope, I replaced the one-way valve and still the vacuum escapes...

Is it an issue that the vacuum slowly escapes in 10 minutes?

If you are a perfectionist ;) My car can operate the popups hours after the engine has stopped :P

Not because the pop-ups won't work after 10 minutes, but because it might be affecting some other part of the cars performance.

Now that you have done the one-way valve, I'm sure it will not be a problem. There's a 1 mm restriction in the manifold connection to the one way valve meaning that even if you run with the headlight system totally unconnected, you will not run into real problems. You may get some unstable idling (though on yours with S-type manifold, it will only affect one cylinder), and you will not run lean at full load: After all the restriction allows an opening of only 0.8 sqmm, whereas one 40 mm port to the carb is more than 1200 sqmm - so the amount of air sucked in this way is very very small.

Your vacuum meter could also be a little leaky?

Fair enough. The car runs much better since I replaced the rubber link pipes so I thought a bit more chasing would be beneficial.

The vacuum gauge was a cheapy, and yes it might leak a bit, but that doesn't explain why the lights won't pop up after 30 mins, or so, of no engine.

It is going so well at the moment, I guess I'll just leave it alone for a bit and enjoy it!

Come to the maintenance day in about 10 days time and I'll show you where the leak is from!


Good to hear.  Did you open up the air correctors from 180 at all?

Roy

???

I am currently employing my best negotiating skills so I can attend the meet! Wish me luck!


No, the 180s are still in the carbs. I'll swap them over this weekend and get the 180 airs drilled to 190.

OK, the negotiations aren't going very well. That is weekend of my wifes 40th birthday and she wants us to spend it with her parents.
Given that, any chance you can tell me where the air leak is likely to be Roy, please?

That's understandable.  Hope you have a good party!


Well if the pipe joints, one way valve, and reservoir are all O.K. that only leaves two places.  If you have ordered a new vacuum operating valve, that is one of them, because I would say it is leaking from the exhaust port.  On old units the spring and/or clip gets rusty and weak and often leaks.  If it is quiet, put your ear near it and you may hear it.  The other place is the double acting servo itself.  By blocking off the servo entirely you can check if that is a problem.

Sorry to disagree Anders but this valve can be stripped and overhauled, as I have done quite a few, but when stripping you have to be careful to note all part positions as there are parts that must go back in the correct way otherwise things will not work.  If you remove the exhaust port clip and spring you must note the exact position first as the pressure must not be too much or too little.  Also you must not lubricate anything with oil which will cause it to stick very quickly.  The rubbers must be clean and dry and a little talcom powder makes a for good lubrication!

Roy

P.S. For the curious, the carbs. were too weak at the top end, and via email (not the ideal way!) I have been trying to get it better set up.  It is now a little rich so the original air correctors which he put back to see how it ran with those, need to be opened up slightly.

Thanks Roy. I thought I had negated that as a problem by attaching the vacuum gauge to the pipe that goes into valve. Unless the vacuum gauge is dodgy, of course.
Anyway, I may have negotiated my way into attending this meet, (I should work for the UN!) so I hope to meet you all then.

Antony