Lotus Elan

WHY DOES THE WHOLE CAR VIBRATE?

PostPost by: Si_130/5 » Tue Nov 22, 2005 11:20 pm

Hi everyone,

I've been looking for a replacement for my yellow car.
Can anyone suggest a cause for a loud booming resonance which vibrates through the body of a Plus Two?
I can say the exhaust has no contact with the engine mount, gearbox, or chassis and isn't blowing.
The alternator isn't touching the body.
The engine is firmly located and doesn't wobble around suggesting (to me) the mounts are ok.
But the noise and vibration through the body is awful whenever the engine turns - tick over, high speed, even on the starter.

The vibrations through the sill tops are almost of a vibro-massage intensity.
The car is on a replacement Lotus chassis fitted by Mick Miller.
When I push the engine over to the n/s while running the sound lessens a bit.
Other than solid metal engine mounts I can't imagine what the cause of the problem might be.
All suggestions welcome. Please ask if you need any more info.

Thanking you in advance for any help you might be able to offer,

Simon :(
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PostPost by: 1964 S1 » Wed Nov 23, 2005 1:41 am

I had a motor mount break in my S1, you had to look close to see it but it was, metal bolted to the engine, resting on metal bolted to the chassis. Check the trans mount as well. The inside of a +2 becomes a drum so it could be a number of things. Do you feel anything odd in the shift lever when experiencing the noise? I'm not sure what you mean by pushing the engine over to the n/s.... I'm guessing broken rubber mount, somewhere.
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PostPost by: type26owner » Wed Nov 23, 2005 2:15 am

Detune it by changing the mass of the engine/tranny as an experiment. Place something heavy like a bag of concrete on top of the head.

If the engine and tranny mounts are old and not oil soaked then they've gotten hard. That would do it.

I had a similiar problem when I was talked into upgrading the tranny mount to this newer style really stiff piece of crap. After I got looking at the damn thing I realized it was installed 90 degrees out of phase so the direction it should have been compliant it was solid as a rock. Trust no one.
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PostPost by: Dave_Newcastle » Wed Nov 23, 2005 11:37 am

I suggest you look closely at the engine mounts - I had one collapse when forced to drive over a high speed bump at eurotunnel by some unsympathetic customs guys - on the way to le mans in 2004. I drove all the way there and back 1100 miles and could not find the cause - car started to run real badly because the carbs were being shaken loose , but was fine at high speeds. Like you I suspected the exhaust on chassis contact but there was none that I could see . Got under the car when home and there it was the metal mount collapsed safely onto the chassis.

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PostPost by: steveww » Wed Nov 23, 2005 4:03 pm

Not sure if +2 engine mounts are the same as baby elan engine mounts but.... I recently fitted some new engine mounts to my S4 as they had started to sag after gawd knows how many years on the car. One of the new mounts only lasted 1000 miles before it gave way. The mounts are an inverted U with a blade inside coupled by some sort of "rubber". Thus they fail safely but this results in a metal to metal contact at the mount. Boy does that send some vibration through the whole car. Difficult to spot but this sounds like what has happened to your +2.
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PostPost by: Si_130/5 » Wed Nov 23, 2005 4:55 pm

Thank you very much for your help Eric, Keith, Dave and Steve. I would have wasted a lot of time looking elsewhere as the under-bonnet (hood) area seemed too clean and well maintained to hide knackered mounts.

Thanks again,

Si :D

PS apologies Eric, by 'n/s' I meant nearside or (UK) driver's side.
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PostPost by: Jason1 » Wed Nov 23, 2005 6:52 pm

Si I have aready emailled you this:



I think the other guys are correct and that the engine/ gearbox mount are the most likely suspects, but;

Sometimes a misfire can cause a car to vibrate, the vibration from a misfire is a lot more noticable on a rear wheel drive car.

I have in the past sped up an idle speed on a car (for a car dealer) to compensate for a burnt valve. The engine appears to run normalish (a little fast) apart from the vibration. The easiest way to check the elan is to run the engine for a while and then put a blob of water on each branch of the manifold, they should all sizzle hot. If one is cold you know it is not firing properly on this cylinder.

It is more likely to be the engine/ gearbox mounts as you mention the noise is also evident on the starter, but I would still check for a misfire just to be safe. If you a concerned about the lack of engine rebuild a simple compression test will tell you it's state in seconds. Halfords do a Gunson "Lo Gauge" which I used about twice a week for five years as a mechanic and still use it occasionally now, they are cheap but good quality.

I never really worried about exact cylinder pressures to manufactures spec as the engines are not new, just ensure the pressure are reasonably even (within 20% of each other). If you have a leaking valve or worn bores you will see instantly low pressures.

If you get a low pressure on one of the cylinders, take out the gauge a sqirt some engine oil in the bore. Then refit the gauge and retest. The oil will temporarly seal the bore for the duration of the test. If the pressure goes up, the bore/ rings are suspect. If the presssure is still very low then the valves are not sealing (valves are a lot cheaper than a cylinder rebore/ pistons and rings).

As you are thinking about buying the car it is best to get a clear picture of what work the car needs so you can negotiate the price (it's too late a week later).

If you like the car don't be put off by the work, but do find out all the facts before you buy.

Hope this helps :)

Jason
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PostPost by: Si_130/5 » Wed Nov 23, 2005 7:31 pm

Thanks Jason,

I'm going back to see it with my tools and I'll take the compression tester too.

Shame it has so many blisters. As the moisture got in through the paint it's a pity I can't just put the car in a paintshop oven and gently bake it out again. I've seen micro blisters disappear in summer.
Am I grasping at straws?


Best wishes,

Si
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PostPost by: berni29 » Thu Nov 24, 2005 2:46 am

Hi Si

I can help you on this one. Yes.

Berni
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PostPost by: Si_130/5 » Thu Nov 24, 2005 11:51 am

Too bad :)
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PostPost by: Si_130/5 » Wed Dec 14, 2005 11:22 pm

Hi again everyone,

Could driving a Plus Two 35 motorway miles with collapsed engine mounts cause any damage or problems?

Si
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PostPost by: berni29 » Thu Dec 15, 2005 2:48 am

Hi Si

If you have any bottom related issues, I would take a soft cushion with you and keep the speed below 80mph.

Have a good trip and look forward to seeing the car when you get back.

berni
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PostPost by: triumphelan » Thu Dec 15, 2005 7:30 am

I have a type 45 which judders when pulling away it dos`nt happen when I raise the rev`s.I have fitted new engine/gearbox mounts about 5K miles ago,they all look good ,I had a new clutch at the same time,the suspension bushes look good,the propshaft was overhauled about 2yrs ago .I can`nt make it judder on tickover or with the rear wheels off the ground and running in gear.It happens when pulling away in either 1st or 2nd gear and with minimum revs
Regards John 1969S4DHC
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PostPost by: Elanintheforest » Thu Dec 15, 2005 7:29 pm

Hi Simon
So long as the windscreen is bonded in really well it should hold up for the 35 miles. Any stress cracks in the bodywork will undoubtedly elongate under such strain, and there will be a risk of the exhaust manifold studs being ripped out of the head. If there are no fatigue cracks in the chassis currently the journey should fix this, and I'd be very careful to check that the spinners don't loosen too much...check every mile or so. The boot lid will act as a giant lever with the lateral vibrations involved and could, if you're lucky, break the hinge pivots or at worse stress crack the body mountings.
No, the biggest worry I fear is fire. The carbs shouldn't froth too much, but some spillage onto the distributor may occur. It's the wires behind the dash that really worry me. Any one of those unprotected spade clips could be vibrated loose and short across a live terminal and....well, you know the rest.
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
Now, if you're still talking to me, can I have your Yellow car logo please until my car is painted? A raw fibreglass Plus 2 is not a pretty sight. And lots of detailed pictures of the new machine...it looks superb and I'm sure :roll: the drive home will be fine.
Talk with you soon...Mark
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PostPost by: Si_130/5 » Thu Dec 15, 2005 8:37 pm

:shock: My pals! Thanks a million Mark and Berni.

Hello triumphelan,

Is it possible you have a slightly torn rotoflex? Does anyone else recognise this symptom?

Si
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