Hi all,
whenever I go over sharp dips in the road I'm getting a terrible thumping noise/feeling coming from the rear. It feels like there's no rear springs and the whole car is slamming down on the rear suspension. My quick initial inspection doesn't show any evidence that the bump stops have been hitting. I've put in new engine & gearbox suspension spring and rubbers. The rear end doesn't seem to be sagging.
Does anyone know whether coil springs lose their 'temper'? (I guess they're 45 years old) I really need to sort this before something breaks or I damage my kidneys,
Regards
Viv

Two things you need to check. Make sure the support bar where the engine mount commects to has no cracks and make sure the support where the spring and motor mount on is not coming loose. My engine mount bracket weld was loose and I had two ceacks in the support bar that caused the bar and mount to flex on bumps hence creating a big thunk. I had it all re-welded and painted and all is good.

So I was in the bank refuting 1200 dollars in charges that someone was putting on my check account because my atm card was skimmed, and I was writing a responce above. Holy crap it makes no sence.

So in my case, the cross member in the rear that the engine mounts to was cracked in two places. When I pushed down on the engine, I could see the two cracks flex. After disassembly, the bracket that the engine mount/spring mount to was also coming off. I had the bracket and cross member welded and I do not hear anymore clunks.

Hi Luxe (not the Toyota vehicle),
it's okay, I did understand your first response. I have looked previously but the rear panel/engine suspension tower seem okay. I'll double check.
It's such a solid thump that it sounds for all the world like the weight of the engine and gearbox hitting the underside of the body.
More suggestions please!!
Regards
Viv

You say you replaced the gearbox mounting rubbers; but that is an area that once gave me trouble when the rubber detached from the steel. It looked OK when stationary but clunked when moving. A variation on that is that there is adjustment in the gearbox mounting cradle as it has elongated slots where the rubber blocks fit in.

Hi Fiat500,
yes the gearbox mounting rubbers are brand new so they're definitely all in one piece. Noted the slots in the mounting cradle that the rubbers bolt through.
I still haven't found the source of the problem!
Regards
Viv

Frustrating! Drive shaft rubber blocks that connect to the back of the hubs; is the rubber OK?
?....Oh, sorry, I see we've already discussed that area.

I just started reading this post as I'm having a similar 'thump' in the back of the car. It didn't do this before I replaced the engine (that I can recall.) In swapping the bell housing of the tranny, I removed the axles and diff together as one unit. It all went back in the way I removed it. Suspension looks fine other than the shocks appear to be pretty old. The center mount for the engine is fine and shaking the engine doesn't produce any thumping noises.

I also replaced the tranny mounts and verified the cross brace they bolt to is secure.

Maybe I'll mount a GoPro under there and go for a ride!

Hi Marcus

I had similar thumping noises, although quite intermittent. I found the 126 sports exhaust I had fitted was hitting the heat shield when the engine flexed over bumps in the road. The movement was sufficient to make a thump when at speed. I repositioned the heat shield up slightly so contact is reduced, fixed it. The 126 exhaust is larger than the stock item so when I manhandled the engine I made the exhaust thump the heat shield. I'm not saying this is everyone's problem or fix, but it was on my car.

Cheers
Hugh Jarce

Hi Marcus et al,
I think I may have solved the 'thumping' problem, I discovered (yesterday) that I could induce the same thumping I get going over bumps by suddenly dipping the clutch and then also as suddenly, 'accelerating'. I believe the issue is the clutch cable outer being too taut or being bolted onto the wrong spot on the side of the transaxle. The outer needs to have a 'relaxed' curved run to allow for the movement of the motor.
Still got to confirm this and try and see if I can get enough extra length in the outer but I'm hopeful.....
Regards
Viv

I had the same issue years ago and resolved it by replacing the rubber inside the spring of the rear engine mount.

I'm pretty sure my problem was the original 500 muffler bolted to the 650 engine. The outlet of the muffler was hitting the underside of the car as the engine moved up and down. Now that I've got a 650 Sport muffler on and proper 650 mounting brackets for it, the exhaust outlet is low enough to not do this. I also installed new tranny mounts and shift linkage at the same time.

However, the engine certainly moves around enough to continue thumping, just not as severely. Maybe it is hitting the air cleaner or carb on the top of the engine bay? If I go over a bump, I can feel the engine move up and down a lot. Disconcerting! Is there a stiffer spring for the mount? I'm using the stock 500 mount bolted to the new 650 engine. I have seen thicker Fiat 126 springs but I'm afraid they're too short. Maybe short is OK? Would that lower the engine some?

Had the same problem when I fitted my 650 engine. The other thing you have to look out for is that the oil filter cover pulley doesnt bounce and hit the spring mount! I got round it all by fitting a stiffer spring and putting a 12mm spacer between the engine block and engine mount. You have to put in longer studs as well. I made my own but you can buy it from van der laan and other places too
Damian

Found a couple of photos Marcus to try and explain my last post
Damian

Damian, what spring did you use? Is this the Type 126 spring? I can machine up the aluminum spacer. Looks like what I need!

I think it was Marcus yes. If I remember when I get home in a couple of days time I'll measure it up for you

Well, I went ahead and bought a reinforced 126 support spring and new 'bumper' plate. They arrived today. I machined up an aluminum spacer to drop the engine as far as the existing studs would allow, so I'm down 0.188" (~4.8mm). Not much, but it may be enough. I went to install my shiny new red spring and it doesn't fit! The spring is definitely thicker wire and shorter than the 500 spring that came out, but it is also bigger outside diameter. It won't fit in either end of the motor mount. Grrr.... Oh well, it goes in the box of all the other worthless stuff I've bought for this car that didn't fit or I didn't need! Maybe I can send it back and trade it for the Fiat 500 reinforced spring.

I also pulled several spacer shims out from under the bumper plate. These are V-Shaped spacers so you can shim the bumper without pulling the whole engine mount apart. Not sure I need them, or if they were making it worse. It seemed to allow more vertical travel of the engine, which I'm trying to avoid. I'll find out on tomorrow's commute if it is better or worse.

You really are not having a lot of luck with this car are you? I salute you for your perseverance though. You will get there eventually and it worth every minute.

How is the engine running now?

Tony

Marcus, i have a spring with some bits that you can have. I bought it in Italy as a 500 replacement spring, but when I took it to a shop they said it was a 126 spring. It is black and I can take some pics for you to see. I can ship it from Cali.

Marcus, are you sure it's the spring causing the problem? I was messing with the mounting on mine yesterday to replace those four little "top-hat" shaped rubbers. When you see how compressed the spring becomes once everything is screwed down it shows :
1. It's a relatively weak spring anyway; mine more so I guess, through age.
2. By the time it's compressed it has become a relatively stiff spring.
I wonder if there is an intrinsic problem with the balance of your engine?