23 replies to this topic

[Pickup76]

Hi Everyone,

I've been having a problem with noise and vibration in my mini pickup since i got it on the road last year. Its far worse than even the stripped out minis i've had before and now i've got to the point where i dont know what to try next.

The problem is present at idle and also quite bad at certain engine speeds (about 60mph in 4th) Its a moderate vibration but seems to be close the the resonance frequancy of the cab as its gets extremely loud in there at this point although outside it sounds no different.

Initally i thought it was lack of good sound deadening so i stripped the interior and completely and totally lined it with silent coat sheets. This really changed the dynamic of the panels, they really are totally dead when you tap them. On top of this is closed cell foam sheets, carpet underlay and luxuary carpet, normal door cards, headlining etc. This made no difference to the problem at all.

Next i targeted the exhaust, its was an 1 3/4" maniflow single box. I then added the centre box and also tried a twin box rc40 but neither made any difference.

I've also tried different combinations of engine mounts, none at all etc plus two more new engine mounts but no effect.

I spent a lot of time looking for any other routes for the vibrations to transfer into the body but cant see anything rubbing or different from any other mini. So at this point i dont know why my car is like this but it certainly isnt like other minis or pickups.

I'm thinking it could be the engine now by process of elimination. Its a 1985 leaded metro 1275 a+ with 25k miles from new (very rusty one owner metro!) I didnt open it up as it ran sweet in the metro but just sprused it up externally changing the relevant bits for mini fitment plus new water pump, new timing cover as it was extremely rusty, new diff output seals and thats about it. It seems to run smoothy from the outside and without much visual vibration watching it. The only thing i can see odd is that the rubber in the crank damper is cracked and perished but i dont know if thats enough to cause an issue. I'm thinking to change it anyway but they arnt cheap!

Any other suggestions/ideas? I'm tearing my hair out!

Thanks
Chris

[racingbob]

first of all I doubt very much its the damper mine was like yours changed it

made no difference

 

get a maniflow 10" rear box and Larger centre one in the middle of the exhaust

 

its has helped mine but still there but not to the same extent

 

speak to maniflow what I said

 

mines around 3300 3500 then goes - its about 60 mph

 

mines 3.4 diff

[RooBoonix]

I had a vibration/noise problem with my RC40. Turns out one of the mounts was pretty much solid so it resonated through the cab. Are your exhaust mounts suitably dampened (rubber mounted preferably),, I have since put the stock exhaust on and now it's a LOT quieter (I have used the proper rubber mounts and now there is no vibration caused by the exhaust)

 

 

Cam.

[Pickup76]

Hi guys, thanks for the replies.

I've actually tried with leaving the exhaust resting on the ground (I welded in a flexi at the front) and also with the rc40 twin box on the end of the maniflow twin box (doubled up) This made it really quiet and would have isolated any noise transmission through the mounts ( rubber square type on front of subframe, two rubber cotton reels on rear) no difference to the cab noise at idle but obviously I couldn't drive it like that to check at speed.

I've had a few people now say their crank damper is like mine and no issues so maybe I really have an engine/clutch/flywheel imbalance.

Chris

[nicklouse]

HIFF carb?

[Pickup76]

Yep hif44

[racingbob]

my crank in my mg metro engine was way of balance

 

did help had it all balanced, but cant get rid of it

 

only tone it down some

[Pickup76]

Ok so i spent a long time playing about with it and discussing with my dad. The vibration appears to be engine speed and this is causing the noise in the cab. So i have a few theories: Something is wong with the clutch, the crank wasnt well balanced from factory (i think less likely), the fly wheel/clutch assembly wasnt well balanced from factory, the clutch assembly was replaced and not rebalanced.

Plan is to replace the flywheel/clutch assembly with a new balanced one and see if it helps. Then i guess if that doesnt work its engine out...

Chris

[cal844]

Id put my money on bulkhead to carb clearence!

[Pickup76]

Id put my money on bulkhead to carb clearence!

Then you'd be out of pocket cal844! I have adjustable engine stabalisers top and bottom so have cantered the engine forward a smidge to give 10mm carb clearance whilst still having some starter and LCB y peice clearance.

[Pickup76]

Update: I decided to pull the engine at the end of last year to get everything balanced and also get more power.

I went for a full k1100 16v conversion from SC using the metro 1275 engine I was running as a donor.


I've just finished the build and the engine runs great and has bags of power but if anything the vibration problem I had before is even worse. Still a vibration at engine speed and bad enough that I start loosing the feeling in my hands driving it. Gutted to say the least.

SC prepared the short engine for me with lightened and balanced crank (with flywheel clutch assy) new Pistons, rebore to 1293cc, original rods.

Is it possible that the 1275 a+ rods were in balance although out of dimension in some way? I can't believe SC wouldn't have checked the balance but I'll ask Tomorrow.

Unsure how to proceed but the prospect of stripping it down again after almost a year of work makes my stomach churn.

[Spider]

It could be from spinning parts but I just can't see it from reciprocating parts.

 

Harmonic dampers are a fairly complex thing, but in brief, they are (or should be) tuned for each engine type and the crank resonances / harmonics of those engine types, or if you wanted to get very anal about it, a specific engine.

 

Have you tried taking the fan belt off and reving it?  Could be one of the ancillaries. If as you think it is related to engine speed, then you should be able to establish this without actually driving anywhere.

 

Have you tried different brands / types of engine mounts? Those that you have may not dampen certain frequencies too well and can in fact amplify some.

 

<Edit: From before to now, what's been changed and what's the same? >

Edited by Moke Spider, 29 August 2016 - 10:18 AM.

[Dusky]

The only thing i can see odd is that the rubber in the crank damper is cracked and perished but i dont know if thats enough to cause an issue. I'm thinking to change it anyway but they arnt cheap!

 

That's enough to cause a VERY serious issue. Replace it asap, and I wouldn't run the car before replacing it. I don't know if you replaced it after the K conversion?

You don't have solid engine mounts by any chance?

 

 

Edit: Spider was faster!

Edited by Dusky, 29 August 2016 - 10:20 AM.

[racingbob]

i cant get rid of my noise at 3400 3500 like a drone then goes

 

i have put genuine engine mounts

 

but didnt make much difference

 

must be something to do with these metro engines

 

balancing the engine did help some but still there 

 

has to be an engine problem

 

as said before i have a 10" maniflow rear and

LARGER mid one, this did help some

[tiger99]

It is not likely to be due to it being a Metro engine, as there are no significant differences. I ran a Metro engine in a Mini for a long time, with no problems, once I had changed the manifold and heater plumbing for the appropriate Mini bits. Of course it sat on Mini mounts too.

 

I think it is time to consider other factors such as, how is the front subframe mounted? Full set of 6 solid mounts with toeboard reinforcement, or 6 rubber mounts? No other combination is acceptable. It the front the original welded steel, or a flip front? Has anything at all, even seemingly insignificant, been modified in the shell? Is the steering column rattling due to worn bushes? (The steering column tends to resonate very close to normal idling speed.)