Stumped!

Post by: **leedsj** » Mon Sep 22, 2008 1:03 pm

Hi all,
I've fixed nearly all of the problems I knew about, but have not yet alleviated the tapping from the engine bay..! I'm now stumped. Let me describe the symptons and see if ANYONE has a clue...

- fast tick, tick, tick noise (about 8/9 a second)
- does not vary in frequency - i.e. it's the same rate regardless of revs - just gets louder
- only occurs under acceleration, even cruising at 60 it's not apparent
- revving in the garage leads me to think it's coming from passenger side / middle at front
- I'm certain it's not the servo (as someone previously suggested)

????

james

Post by: **enskr** » Mon Sep 22, 2008 1:23 pm

electric cooling fan blades contacting the fan mounting frame / radiator?

Kevin

Post by: **leedsj** » Mon Sep 22, 2008 1:32 pm

hmm... have considered it - but was thinking that would be faster?

Post by: **enskr** » Mon Sep 22, 2008 1:53 pm

Maybe - might only be 1 blade per revolution that touches something though. It should be obvious as you will most likely have a corner missing from the blade(s). It fits with the position if not the "only under acceleration" bit (unless the engine twisting on it's mounts is pulling something into contact) It's hard to think of anything else which has a rotational frequency independent of the engine revs.
Kevin

Post by: **ppnelan** » Mon Sep 22, 2008 3:48 pm

Something to do with the headlight vacuum circuit?

:arrow:

Matthew

Post by: **peterako** » Mon Sep 22, 2008 4:13 pm

leedsj wrote:Hi all,

- fast tick, tick, tick noise (about 8/9 a second)
- does not vary in frequency - i.e. it's the same rate regardless of revs - just gets louder
- only occurs under acceleration, even cruising at 60 it's not apparent
- revving in the garage leads me to think it's coming from passenger side / middle at front
- I'm certain it's not the servo (as someone previously suggested)

????

james

I have the same symptoms......BUT at DECELERATION!!

Would love to know what it is......

My main mechanic suggested a work tappet bucket top (the tapping occuring when as the bucket rotated increasing clearance). But it only happens at decelation....or fast return to idle.

(Occassionally at idle too for short bursts)

........Lotus gremlin???

Peter

Post by: **elanman999** » Mon Sep 22, 2008 4:27 pm

James,
Is it the vacuum non return valve for the servo. This can cause a ticking sound if it is attached to or touching the bulkhead. As standard it is situated in the middle of the bulkhead just above the rear of the head.
Cheers
John

Post by: **leedsj** » Mon Sep 22, 2008 5:14 pm

ppnelan wrote:Something to do with the headlight vacuum circuit?

Matthew

elanman999 wrote:James,
Is it the vacuum non return valve for the servo. This can cause a ticking sound if it is attached to or touching the bulkhead. As standard it is situated in the middle of the bulkhead just above the rear of the head.
Cheers
John

I presume that you're both talking about the same thing... I'm thinking this could be related to my recent 'lights easily pop-up' phenomenon

one thing - what does a vacuum non return valve look like?

Post by: **tdafforn** » Mon Sep 22, 2008 5:48 pm

do you have an electric fuel pump?

Post by: **tvacc** » Tue Sep 23, 2008 4:25 am

I know you would think that this would have to increase with engine speed...but have you thought of the timing chain hitting the top of the valve cover. Easy to check by taking off the valve cover and looking at it.

Post by: **elanman999** » Tue Sep 23, 2008 9:37 am

James,
Pic of vac valve. It's the alloy bit in the middle that joins the rubber tube to the steel tube. Mine is attached to the bulkhead, otherwise it flops about in the breeze.
Cheers
John

Post by: **twincamman** » Tue Sep 23, 2008 6:53 pm

Pertaco is right on the money ----a bucket didnt get back in its correct hole ----so it taps ---ed

Post by: **leedsj** » Fri Sep 26, 2008 2:32 pm

elanman999 wrote:James,
Pic of vac valve. It's the alloy bit in the middle that joins the rubber tube to the steel tube. Mine is attached to the bulkhead, otherwise it flops about in the breeze.
Cheers
John

I don't think it's the fan, as tweaking the throttle standing in the garage causes the sound but the electric fan is not spinning... however, I can't find the vac valve! is it close to the vacuum-ball-cock?

Post by: **M.J.S** » Sat Sep 27, 2008 9:19 am

Do you have electronic ignition?

If so the rotor disk in the dizzy (don't know its technical name) can raise the height of the rotor arm and cause it to touch the contacts in the cap. Check the wear on the contacts for any signs of rubbing. It will give a light, hollow but annoying knock.

On mine with Lumination ignition I had to file a few thou off the rotor arm so it sat back at its original height to stop it catching, after ruining the cap and annoying me for weeks. :roll:

Mark.

Stumped!

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