Help...banging from the rear of car

[esprit17]

Hi all,

I have a very concerning, thud, thud, thud (x3) when accelerating say above 50% throttle and again when I lift off.

It tends to happen in the low gears 1-4 and up to around 50mph.

I had no issues until I replaced the clutch (OEM) and replaced the input shaft as it was burred

I have checked and replaced the basics

x2 engine mounts (1 had collapsed)

x2 gear box mounts

All chassis mounting bolts tightened

Bulk head bolts tightened.

The above have made a difference but it definately still there.

All other transmission components have been checked and appear to be fine, drive shaft, CV's, exhaust mounts etc.

The specialist garage is stuck, and is suggesting leaving it to develop in order to diagnose it.

Obviously I am very nervous about doing this, so if anyone can give me some ideas of what else to check that would be great?

I'll see if I can record it

[andydclements]

It could (but I doubt that's it) be a CV joint getting worn, showing signs only when under a large load.

[ramjet]

Did you lock someone in the boot?

[Advantage]

I wonder if it's worth stripping the driveshafts out of the hubs and inspecting the splines on both items.

[esprit17]

Did you lock someone in the boot?

Just the previous owner, for selling me a dog!!

[richardvg]

Maybe you locked two people in the boot ,hence the constant banging .I remember the days when i had a camper kombi and my mate used to drive whilst i ..................................................................didnt think i would really tell.

hONESTLY THOUGH - CHECK THE GEARBOX .

[esprit17]

Hi Guys,

right i've uploaded to you tube, basically as i've said there is a banging noise when putting your foot down (50%+) throttle in the lowere gear.

hope this works

any thoughts, even stuff you think it is definately not will help narrow it down

thanks

[Sparky]

So difficult to say from that, but: exhaust? Was an exhaust fitted while you had a collapsed engine mount, and now it's resited, the engine torque throws it against the body? WIld guess...

[ramjet]

I'm with Gary. I think exhaust or some ancillary component. As you have not changed speed in the video, I can't see it being associated with anything rotational as it starts and stops and it's frequency isn't fast enough for the speed you are doing. Does it sound like it comes from the right or left side or directly behind?

I presume from your description that it does not occur when stationary? Have you hopped under the car when cold and started hitting things with your hand to see if you can replicate the type of sound?

Michael.

[esprit17]

I'm with Gary. I think exhaust or some ancillary component. As you have not changed speed in the video, I can't see it being associated with anything rotational as it starts and stops and it's frequency isn't fast enough for the speed you are doing. Does it sound like it comes from the right or left side or directly behind?

I presume from your description that it does not occur when stationary? Have you hopped under the car when cold and started hitting things with your hand to see if you can replicate the type of sound?

Michael.

thanks ramjet,

I am accelerating at the time, just opening the throttle +50% then quickly off, it also happens when I lift off.

A the moment the sound is just from the back, it is very difficult to even tell whether it's left or right.

sadly it doesn't happen when stationary so I am toying with the idea of puttinf it on a rolling road, but I'm not confident with all that roller noise that I'll actually hear it.

I'll have a bang about at the weekend

[ramjet]

Can you 'feel' anything going on when it happens? Through your hands on the wheel or through your butt on the seat?

[esprit17]

Can you 'feel' anything going on when it happens? Through your hands on the wheel or through your butt on the seat?

nothing through the sterring wheel, just a couple of thuds that can be felt through the seat. Just though of something that I need to check, the R/H fuel tank was replaced and may not be secured correctly but there again I would expect the noise to be present under heavy braking.

[nodemgr]

My 4 cyl does something very similar, except it's only when I press the throttle while in a high gear going slowly. And it's only the initial knock, I don't get the subsequent knocks.

I was under my car and the left driveshaft makes a clear clicking sound when I rotate it by hand. Sounds like the inner CV joint has no lubrication. I plan to take a look at it this winter. I didn't think the two could be related, but possibly.

[gmendoza]

Sounds to me like the bulkhead. Here's one fix:

http://www.lotusespritworld.com/EGuides/EModifications/BulkheadPlate.html

[Rob C]

Hi Steve, good cars the V8's aye. maybe I can help... It may well be the Radius Arm Mounts, very difficult to check and actually see. My car is 10 years old, but spoilt to bits.

This part dates back from the very early cars...like my ex Elite V8..1974.

Today they are now Poly type..about £60 for a pair from the factory. Its possible you have one or the both shot.... then its possible the actual Radius Arm's large mounting Bolt

could be hitting the Chassis under load and also slowing or braking. What is your cars road handling like on and off the gas..?

Have photo's ..use my email .........

regards Rob

[HowardRoark]

Sounds to me like the bulkhead. Here's one fix:

http://www.lotusespritworld.com/EGuides/EModifications/BulkheadPlate.html

I found this Bulkhead fix and it was just what I needed! I heard such a clunk sound any time I would go over a bump. I read this article and fix, and thought it had to be it. It was! I printed out the article, took it down to my Lotus servicing dept, and they did exactly what the article said to do - fix the bolts so the bulkhead wouldn't rattle anymore.

After fixing, it is like night and day. It is so much more solid! THANK YOU Rob Stansfield for writing the fix article to the bulkhead problem!!!

Thanks, Matt

[esprit17]

Hi All,

Problem has been solved by replacing the engine mounts with Sport 350, although the orginal and newly replaced ones were for all tence and purposes 350's

Bit of a wild goose chase as I discounted the engine mounts as they were new but sourced independantly so although I trusted the providence it means no come back.

Anyway the good thing is up and running, bad thing now working abroad so don't get a chance to drive it.

Back this weekend though if anyone is out in the NE of England fancy a blast?

Thanks for the support and pointers, another lesson learnt, just cause you have replaced something doesn't mean it works !!!! obviouse but kept the car off the road for months.