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Vacuum line sealing in rubber elbows - Interior/Exterior/Lights/Glass/Alarms/ICE/HVAC - The Lotus Forums #ForTheOwners Jump to content


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  • Gold FFM

Since the day I got my Esprit it has been suffering with the vacuum pump constantly running. I've previously done some diagnosis and ruled out the pump as the cause and I know the fault is not on the engine bay side of the T-piece immediately after the pump, so the fault is somewhere between that T-piece and the long run down into the cabin.

I ordered a whole bunch of replacement rubber joiners and elbows hoping it was them that had gone hard with age and were allowing the air into the lines, however the new rubber pieces don't appear to have made any difference. While fitting them there didn't seem to be much resistance between the thin black pipe and the rubber connections, so my best guess at present is the vacuum is still being lost at these junctions.

Should there be any supplementary seal between the thin black pipe and the rubber connections that I'm missing; should they be glued together for example? Or is there another common culprit I've overlooked that is causing the lack of vacuum?

Edited by tomcattom
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Norfolk Mustard S4s #1 :)

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I used a bit of heat shrink over the joints, no more leaks

I had similar issue and traced it to the T piece under the drivers quarter panel on top off fuel tank. Another common culprit is the elbow by the heater matrix. Good hunting!!

I decided to revisit what I though I already knew and it seems that since I did my first testing my vacuum pump has ceased functioning correctly. When I did my previous testing I'd isolated the pump a

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  • Gold FFM

The rigid pipe should be a snug fit into the rubber sections.

its easy to rule out problem areas and narrow it down by pulling the inlet to the tee off and blocking it with your finger - that should stop the pump and proves that section is ok or has a leak

There’s three elbows under the steering wheel - look at those and replace

Only here once

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I used a bit of heat shrink over the joints, no more leaks

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Tom, I you haven’t already done so, may I suggest getting a parts manual? They’re available online here if you upgrade to a FFM. The rubber elbows, pipework and heater vac valves are shown in there.

Vacuum will definitely be lost if any of the connections are slack. They need to be a tightish fit, assuming you’ve ordered the correct parts. 

Margate Exotics.

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  • Gold FFM

I've got the part manual thanks.

Based on my investigations last night when I posted I think the fault is somewhere between the first T-piece after the vacuum pump and the long run down the car into the cabin because when I disconnected the pipe under the dash and blocked it off the pump kept running, so my guess is there is either damage to the long thin pipe running down the car or a leak where the pipe joints the T-piece by the pump on the rubber reducer that connects it to the T-piece by the pump.

The join by the pump didn't seem all that snug which I why I was wondering if it needed some sort of adhesive/seal assistance. Its a new joiner, but it could have been sat on a shelf as long as the old part had been on the car I suppose!

I might give the heatshrink idea a try tonight.

Norfolk Mustard S4s #1 :)

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  • Gold FFM
6 hours ago, chris said:

I had similar issue and traced it to the T piece under the drivers quarter panel on top off fuel tank. Another common culprit is the elbow by the heater matrix. Good hunting!!

I wasn't aware of a T-piece by the fuel tank when I investigated. I must have been looking at the wrong page in the parts manual. I'll take a look for that one tonight.

Norfolk Mustard S4s #1 :)

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I don't know about earlier models, but for sure there's no T-piece by the fuel tank on my S4s. The single vacuum line runs straight from the pump, up below the engine bay trim panel, up behind the RH cant rail, and down behind the A-pillar post to a single T-piece under the dash. This feeds each of the two vacuum switches. Each switch then feeds/controls a vacuum actuator, one for the fresh air/recirc, the other for the mode.

EDIT Just remembered - have your EBPV and throttle jacks been disconnected? Mine have hence the straight run, but if not, there should be a T-piece residing in or just behind the box with the pump, see the vacuum line diagram which will be on the underside of your tailgate. These are another potential source of leaks.

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Margate Exotics.

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  • Gold FFM

EBPV and throttle jacks are still connected. When I disconnected the long pipe to the cabin from the T-piece near the pump and blocked the open end off the pump shut up after a matter of seconds, so that fault definitely isn't in that section of the system.

Norfolk Mustard S4s #1 :)

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  • Gold FFM

I decided to revisit what I though I already knew and it seems that since I did my first testing my vacuum pump has ceased functioning correctly. When I did my previous testing I'd isolated the pump and proven that it would shut off when I stuck my finger over its outlet, hence the belief that the fault was in the pipes somewhere. When I tried the same test again the other day, the pump wouldn't shut off at all, so either a sensor inside has failed, or my my likely suspicion is that it was generating a very weak vacuum before and it wasn't enough to shut the pump off with all the pipes connected.

Long story short, thanks to Mr Kearley I now have a replacement pump, with the foam pack which mine was missing, and all appears well again on the heater controls front.

Before :(

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After :)

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Norfolk Mustard S4s #1 :)

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