cross member vacuum tank

[Dave_Newcastle]

On a failsafe system what function does the vacuum tank perform?? I have been looking at past postings but still dont fully understand what is going on.

On a non -failsafe sytem I believe it is needed to keep enough backup vacuum to keep the lights up at night under all engine conditions.

Through testing I have a vacuum leak in either the non-return valve, the t - piece or the crossmember tank and the head lights were lifting ten minutes after the engine is switched off.

Have been looking for this leak morning and as some may know from their own experiences, it is very frustrating to locate. However I have found that I can fix the lights from raising with the engine off, by placing a second none return valve beteen the crossmember tank t piece and the solenoid valve so the system in order is now:

headlamp actuator pod
solenoid valve
additional none return valve
t piece/crossmember vacuum tank
original none return valve
manifold.

Can the car be run like this?? or will I have some problem????

Which is why I ask the first question - what function does the vacuum tank perform perform on a failsafe system since the headlamps on a fully functioning original system would be held down by the original none return valve??

Any observations or advice would be much appreciated

[rgh0]

The vacuum tank in the failsafe system provides the vacuum reservoir to help hold the lights down for extended periods of non operation of the engine and to ensure instant response in retracting the headlamps by having a substantial vacuum volume available at all times.

You can live without either, as neither are critical compared to keeping the headlights up in a non failsafe system at full throttle

regards
Rohan

[Frank Howard]

Have been looking for this leak morning and as some may know from their own experiences, it is very frustrating to locate.
Any observations or advice would be much appreciated

Dave,

I've experienced the same problem in the past. I narrowed it down to the two connections at the switch right behind the dash board where the right angle plastic connectors are. Take both connections apart and smear a little grease on the joints. That should help with the seal. Let us know if this helps.

[Robbie693]

My problem is a leak in the crossmember. It's bypassed at the moment so there is not enough vacumm to hold the lights down for more than a couple of hours. They are also a bit slow to retract after flashing. If only I could pinpoint the leak...

[mikealdren]

Robbie,
It's probably a leaking weld somewhere but vacuum leaks are harder to find than 'pressure leaks'. You could simply put sealant over the welds.
Alternatively, how about rigging up a feed from a compressor to pressurise the crossmember, you can then search for leaks with the soapy water.

Good luck
Mike

[Robbie693]

Thanks Mike,

I did have a go with a compressor and blowing down a tube but couldn't find anything. Maybe my soapy water wasn't bubbly enough! Didn't think of the sealant - would normal silicone do?

I intend to strip the paint off as it's peeling (spider chassis) and repaint and I'll have another go then.

Another idea I had was to use the stuff for sealing the inside of petrol tanks but I don't know how this is applied. If you have to swirl it around to cover then this would be difficult obviously!

Cheers

[Emma-Knight]

Maybe stupid but ... doesn't a spyder chassis cross member have drain plugs at the bottom?

Anna

[Robbie693]

Maybe stupid but ... doesn't a spyder chassis cross member have drain plugs at the bottom?

Yes it does Anna. I sealed that up but still have a leak somewhere...

[Dave_Newcastle]

Thanks Guys.

My mind is at rest now and my headlamps have stayed down for nearly four hours.

Off to Le Mans in the car tomorrow so feeling pretty much in the holiday mood now. I think this is something to do with having stopped packing the emergency tools and spare parts at the bottom of the boot and now putting in my sun cream, bottles of beer, chair and radio.

Dave

[andyhodg]

Robbie

I had a leak in my Spyder crossmember. I located the leaks - (yes more than one) by filling the cross member with water which I then pressurised using the pressure from the water system. Not ideal I know but I figured that whatever remedial work was needed would adequately dry the inside of the crossmember out.

It turned out to be cracks in the crossmember where the wishbones attach. I asked Spyder to weld the craks and fit reinforcement patches. (I had noticed that the zetec chassis has these reinforcement patches fitted).

Unless you have the facilities to ensure that there are now petrol fumes i the crossmember leave any welding repairs to an expert.

Good luck

Andy

[Robbie693]

Thanks Andy,

I'd not thought of putting liquid on the inside, not a bad idea.

The car hasn't had the vacumm system fitted for over 15 years apparently, apart from my attempts to get it working, so I guess fuel vapour is not so much of a problem. Having said that, I'm no welder and wouldn't trust the car to anyone that wasn't familliar with it.

I had thought of asking Spyder to have a look, would you mind telling me how much they charged and how long it took to do? Sorry for the cheek, PM me if you like..

Cheers