Lotus Elan

I'm pickin' up bad vibrations

PostPost by: StoatWithToast » Mon Jun 28, 2010 11:30 am

Hey,

Finally got the car back on the road Saturday. Various bits serviced, 4 brand spanking new (and damn expensive) rotoflexes fitted, new HT leads, new plugs, all new air intake system, diff seal replaced (still leaking) and re-oiled major parts plus various electrical bits sorted.

We weren't planning on doing the rotoflexes, but one was sheared through and the other 3 were all split. I also had a really bad vibration at speed. It felt like there were two at different frequencies and they were beating to cancel out and then get really bad.

Started up and purred lovely. First 10 miles were silky smoth. Another 10 miles and the vibration was back, another 10 and it was as bad as ever.

I need to check the rotoflexes out, but if they are broken, what should I check on the suspension to see what is killing them so quick?

Anything else it could be?

Cheers,

Dave
Last edited by StoatWithToast on Tue Apr 19, 2011 5:34 pm, edited 1 time in total.
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PostPost by: types26/36 » Mon Jun 28, 2010 12:15 pm

Check that the diff is not touching the chassis after they worked on it, are the mounting bolts tight and also the rotoflex bolts tight ? are the propshaft bolts tight?
Also check that one of the engine mounts have not collapsed.
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PostPost by: oldelanman » Mon Jun 28, 2010 12:18 pm

Hi Dave,
I'm sure you know this but the rotoflex's can be fitted wrongly......the bosses are offset to match up to the legs on the driveshafts. If you fit them wrongly it will cause early failure and may even give rise to vibration because the rubber is distorted and more stressed.

Other possible causes of vibration are loose wheel nuts, bent wheels, tyre run-out, wheel/tyre imbalance, loose diff flange hardware and worn propshaft u/j's. I'm sure there are others too but those things come to mind.

It's strange that the vibration did not start straight away but built up over a distance. Once it's there is it constant or does it vary with speed, load, braking or cornering etc?

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Roger
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PostPost by: billwill » Mon Jun 28, 2010 12:33 pm

>We weren't planning on doing the rotoflexes, but one was sheared through
>and the other 3 were all split. I also had a really bad vibration at speed.
>It felt like there were two at different frequencies and they were beating to
> cancel out and then get really bad.


Ouch yes, always check the rotoflexes closely on any recently acquired car and at least once a year (part of your own MOT pre-check, because am MOT tester might not look for that and it is difficult to spot a damaged one unless you know what to look for).


It's very dangerous, I imagine, to drive with damaged rotoflexes because it it gave completely there would be a half-shaft flailing around at the back doing enormous damage and danger to life


PS: Some topics on fitting doughnuts.
elan-f14/replacing-the-doughnuts-t16456.html?hilit=%20doughnuts

elan-plus-f13/amazing-tip-replace-rotoflex-donuts-t20272.html
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PostPost by: billwill » Mon Jun 28, 2010 12:46 pm

I get the impression that you had someone else fit the doughnuts, not yourself; did they have a copy of the lotus workshop manual?

If not as mentioned above, they might have fitted them wrongly, inside out or with the nuts on the wrong sides. All the nuts should be on the Diff side of the fitting.

Some vibration noises are harmless, for instance my exhaust pipe vibrates against the gearbox casing, annoying but not dangerous.
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PostPost by: StoatWithToast » Mon Jun 28, 2010 1:16 pm

The tyres are new and freshly balanced, so I don't think it's them. And because it was so smooth after new rotoflexes went on then got worse that's the only thing I can think of.

It is speed related, but as I say, it is as though there are 2 vibrations of different frequencies, the cycle in and out of phase being really bad (like the doors might fall off bad) the not at all then back again, over and over.

Most of the work was done myself, but we were running out of time so mid-week my father and grandfather kindly did the rotorflexes for me. They did have the manual (Lotus) and the addendum (Brian Buckland). I asked them to read both very carfully before doing any work while I wasn't there because they can be a law unto themselves when they get tinkering on any car.

The ones they took off were an old and a newer pair, but the bolts were all in wrong. However, they took 7 hours to fit all 4 and said it was hard work getting the holes in the rotoflex to line up with the spiders (which I thought was odd as Brian clearly said he could do them in 20 minutes, even each with tea breaks that's less than 2 hours)... now you have said there's a location for each and that they are offset I am bricking myself! I will have as good a check as I can tonight (no pit or lift).

We're taking the Elan to Le Mans Classic next Wednesday and we're going for an engine tuneup that Wednesday. This weekend we are booked solid with other work (we're still trying to get the paperwork for the XI sorted).

Gosh Darn It!
Dave
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PostPost by: types26/36 » Mon Jun 28, 2010 2:05 pm

StoatWithToast wrote:The tyres are new and freshly balanced, so I don't think it's them


I had a vibration as you describe, it was a tyre delaminating but it was an old tyre.....but you never know :?
Of course......the wheels are tight aren't they :roll:
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PostPost by: bcmc33 » Mon Jun 28, 2010 4:11 pm

types26/36/74 wrote:
StoatWithToast wrote:The tyres are new and freshly balanced, so I don't think it's them


I had a vibration as you describe, it was a tyre delaminating but it was an old tyre.....but you never know :?
Of course......the wheels are tight aren't they :roll:

Do a simple verification test -- change the wheels from front to rear, to see if the vibration still exists.

Double check the diff mountings that has already been mentioned - if they are OK, then it's back to the donuts. :cry:
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PostPost by: billwill » Mon Jun 28, 2010 5:40 pm

Fitting a set of doughnuts could easily take 7 hours if its the first time you have done it.

The link I gave above shows my way of doing it (includes photos).

One main snag for newcomers is that they believe the strapping bands supplied hold the holes in the right positions, which is rarely the case, so I always replace the supplied strap with 3 jubilee clips in series.

The 4 doughnuts are identical, it's just the bushes that are offset; lay one on a flat surface and you will see that 3 bushes are contacting and 3 are "in the air", flip it over and those 3 are the ones now on the flat surface. The 'protruding' 3 are the ones that should be in contact with the Diff spider ot half-shaft spiders or wheel hub spider. In the manual they call them 'high bosses'.
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PostPost by: alexblack13 » Mon Jun 28, 2010 7:27 pm

Hello Dave /all,
Vibrations are a pain in the ass are they not? Dave, when you had the diff' out did you have a fondle at the prop shaft joints? Just a thought but it looks to me like you have covered most other causes.

On the diff leak. You say its still leaking! points to something other than just the seal being faulty / worn out. Poss' reasons could be wear in the nose pinion where it lands the seal. Pitting? worn? etc... The other cause of oil leakage at the nose seal is a failure to apply some sealant to the metal outer ring and clean the seal area of the diff'. I know this from having replaced the nose seal and it still leaked also. I took it out again and chucked it before carefull cleaning and refitting the new one with some sealant seal - diff'. Sorted...

I hope you find the problem before next week and look forward to giving you a call when 'on site'. I am confident you will.

C U there..

Alex..... 8)
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PostPost by: kstrutt11 » Thu Jul 01, 2010 10:01 am

alexblack13 wrote:Hello Dave /all,
Vibrations are a pain in the ass are they not? Dave, when you had the diff' out did you have a fondle at the prop shaft joints? Just a thought but it looks to me like you have covered most other causes.

On the diff leak. You say its still leaking! points to something other than just the seal being faulty / worn out. Poss' reasons could be wear in the nose pinion where it lands the seal. Pitting? worn? etc... The other cause of oil leakage at the nose seal is a failure to apply some sealant to the metal outer ring and clean the seal area of the diff'. I know this from having replaced the nose seal and it still leaked also. I took it out again and chucked it before carefull cleaning and refitting the new one with some sealant seal - diff'. Sorted...

I hope you find the problem before next week and look forward to giving you a call when 'on site'. I am confident you will.

C U there..

Alex..... 8)

When I bought mine, it was fine on the test drive, but after a few miles on the way home (from Hereford to esesx) vibration started and was pretty bad at anything above 60mph, got it home Ok and found the pinion flange nut was loose, I had a spare diff from a Escort which was the right ratio so I fitted that' its been fine since, but you could posible get away with just tightening it if the bearings etc are not damaged.
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PostPost by: elansprint71 » Thu Jul 01, 2010 10:39 pm

Has anyone here actually tried to put the couplings in the wrong way round? You would have to be pretty determined to actually get them in that way. :roll:
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PostPost by: oldelanman » Fri Jul 02, 2010 9:59 am

Has anyone here actually tried to put the couplings in the wrong way round? You would have to be pretty determined to actually get them in that way. :roll:



Never tried it but they might actually go in more easily the wrong way round as the offset of the bosses would give you more space between the driveshaft spiders.

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PostPost by: StoatWithToast » Fri Jul 02, 2010 1:35 pm

Thanks for the ideas. I'll have to try and stick my head under to check the bosses are right tomorrow, I think they are. The bolts may be wrong - they were on the diff side when we took them out, so they may have put them back in the same way.

Hmmm, think it could be that nut. It was really loose when we took it apart to change the seal. When we checked the manual to torque it back up though it only said something like 40ft-lbs to hold it... Considering the XI took 140 that seemed really low. We decided the book would know better than us, and that it was probably self-tightning (like the wheel spinners) too.

Real pain as I don't have the tools or space to sort this out pre-Le Mans now... bottoms!
Dave
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'72 Sprint FHC (and staying that way) - 0479
'65 XI Replica
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PostPost by: StoatWithToast » Fri Jul 02, 2010 2:06 pm

Just looked at the DHC for sale on Caslte's website - the rear is a good couple of inches higher on that car... I think my rear suspension needs sorting out too... Another one to add to the ever growing list :)
Dave
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