New vibration after recent work

[olr159w]

I have a Sprint. It sounds different after work recently completed. Seeking some opinions.

The work completed was new poly bushes on the front suspension and rear sub frame mounts. Regarding the latter I've used a spacer tube on the NS because the protruding tube from the chassis leg was absent. I made this first of all using a cut down top hat spacer per the front sub frame mount and secondly from some regular 16mm steel tube.

When I first drove it there was a noticeable vibration noise particularly at idle. Not an engine sound but a contact knocking type of mid-low freq noise. I suspected the use of the top hat spacer because it was a fairly close fit through the hole in the sub frame. The top hat spacer OD was nearly 21mm. I replaced it with a piece of pipe of OD 16mm.

I might be deluding myself but I don't think so. With the alternative tube the problem was greatly reduced. I just ran the car around the block a couple of times again where it got up to temp and then left it running in the garage while I had a poke around. Five things :

1. the vibration noise is still there but only specifically identifiable at idle (900-1000 rpm indicated). It sounds worse inside the car than out. The car is noisy enough in general that its hard to be certain the vibration noise is there the rest of the time
2. the car seems noisier than it was in general to me although I haven't driven it for quite a while. Almost tempted to say the exhaust might be slightly blowing at the front but then it could be this vibration thing
3. vibration manifests itself as noise rather than noticeable feeling through the car
4. with the engine running I placed both hands on the camshaft cover in a noise damping way ie without applying pressure. It made no difference. I then pushed the engine from NS to OS. It doesn't move much obviously but doing this stopped the noise.
5. increase the revs while stationery and the sound goes (or is drowned out). I think it goes

The exhaust front pipe is shaped to go around the sub frame anyway but I'm fairly sure it's not touching as a result of the work done. I have a slight fear that when I first lowered the car with the shocks back in place they were set very low and the resulting angles may have caused some type of pressure on the exhaust system. This is as much a hunch as anything but the car did sit very low because I hadn't wound up the shock seat height adjusters enough.There was some type of noise when I lowered it

My theories :

The engine runs well and this doesn't sound like an engine sound. It sounds like a vibration. I wonder if it is still the spacer tube but at this point I'm using a regular size bit of pipe that should have around 2.5-3mm clearance from its walls to the sub frame spacer hole. I note that changing this spacer did seem to improve things but it's hard to imagine how it is still impacting (if indeed this ever was the issue)

It's odd that leaning on the engine a bit causes the vibration to stop. It tends to imply the vibration is NS - where we have the slightly rogue sub frame mount and the exhaust. I would the sound is NS or centre

Prior, the NS sub frame mount had no tube and was just clamped against the washer bush. With everything tighter this may possibly have raised the sub frame to hit the exhaust.

Or, given it seems a bit noisy when driving, perhaps I'm confusing the sound and the exhaust is blowing slightly; this being something changed slightly when the engine is leant on. But I drive modern cars most of the time and the general noisiness is probably something I've forgotten

I haven't yet sat under it with it running and used a screwdriver as a sound localisation prong. Something for tomorrow.

In the meantime any views very welcome.

[tony g]

I doubt its anything to do with the subrame/chassis connection.
To me it sounds like either :
The starter solenoid is touching the chassis- these can be very close on a sprint and when the engine mounts sag or are misaligned can be worse.
The stabiliser bar at the front NS is grounding out maybe?
The exhaust downpipe is touching the footwell or chassis.

Im sure more will add to this but its a start

Tony

[Jon Tilson]

Downpipe is just touching the subframe...this is very common after this type of work and is bizarelly hard to spot.

On one car I had you could only see it on a garage lift, but it was then obvious and was cos the subframe was too close
to the body...back spacer bushes not thick enough.

That explains why it goes when you push the engine towards the drivers side...

Jonners

[sprint95m]

From my experience I concur with Jon and Tony,
it'll be the front pipe touching the subframe.

It may be worth looking at the gearbox mount...?


On the Sprint I had,
I solved this problem by first heating up the subframe rail and then reshaping by tapping it down
thereby providing satisfactory clearance.



Ian.

[olr159w]

It makes sense folks thanks.

The car has the wider front pipe and a straight stainless exhaust. When it was rebuilt the front pipe was rendered a bit pointless by being beaten to 2/3 diameter to get it to not coincide with the subframe.

It does seem likely that with changes to the NS sub frame mount this known issue has arisen again. It makes total sense. It just that I can't see it is touching, although take your point on that fully Jonners.

The second spacer is a copy of the first and that is only 20.5mm long vs the 22mm I was advised to make it. I can't exactly recall why I did that but I think it was because the washer bush didn't appear to compress enough otherwise. Or I could be going mad. It's all been on and off the car a few times........ I will make another that is 22mm and see what happens

m

[olr159w]

I've tried the sub frame mount with a 22mm spacer and now with a 24mm spacer. When I first did it the spacer was a bit under 21mm.

Two things I suppose. Firstly I'm not entirely convinced this spacer tube isn't reshaping the chassis leg on being tightened up. Now I'm using regular narrow tube rather than the thick walled top hat spacer tube I wonder whether the compression point load is that much higher. Right now the thing is only moderately tightened and yet the washer bush still looks quite compressed.

So I can see the whole lot will likely come off again before too long. More chemi-metal coming up......

Second, the way it is right now I "think" the vibration has gone. It's hard to tell. The vibration was at idle. I do think that is better. But somewhere in the 1000-2500 rev band there is a louder more "boomy" noise that then goes once the revs are higher.

Is it still this vibration? Not sure. I'm feeling it's more like an exhaust noise but then this would just get worse with more revs so......?

At least its all a lot better than it was.

[Carledo]

From the pic on your axle leak thread, my Spidey sense tells me you have a Rimmers stainless sports exhaust (or very similar facsimile) fitted.
This product is widely known amongst members here for developing odd booms and sympathetic resonances at various points in the rev range. So your suspicions may have some foundation.
I have one of these myself and so far it has not done anything untoward (it's only just over 2 years old) but the note HAS altered with time. And with the diff whine, gearbox howl, noisy high pressure fuel pump, squeaky polybushes and total absence of carpets and soundproofing in my car, I may have missed one more noise!

Steve

[olr159w]

I can't remember where the exhaust came from. I know it had a guarantee and years on I made them honour the provision of a replacement tailpipe. But yes your spidey sense is correct re a stainless sports exhaust.

It could just simply be that. Or the process of somewhat over-lowering the front of the car may have caused some leverage on the exhaust joints. By over-lowering I mean when first replaced the shocks seats were adjusted so low that the jack barely fitted under the spoiler. There was a minor odd sound at the time. Could have been anything but just makes me wonder.

That said if the exhaust was blowing it would get worse as the revs increased and that's not the case. Something to live with and see what develops

m

[olr159w]

See here first : viewtopic.php?f=4&t=32294

Time has moved on and if anything the issue is worse.

The engine runs reasonably smoothly and as far as I know the exhaust remains good, at least externally ie its not blowing.

The noise at certain revs - lower revs mainly - is fairly unpleasant. It's noticeable outside the car but isn't too bad. Inside the car it's very noticeable and annoying. I was under the car again yesterday and took some pictures. It feels fairly obvious to me that its caused by the exhaust downpipe hitting the subframe. I'd commented before about the downpipe having been modified to clear the subframe is the first place - something I wasn't too thrilled about at the time.

Now though I just feel sure it's hitting the subframe at certain revs - worse around idle and better at speed when perhaps the engine is running more smoothly.

The question is why has it got worse. There can only be one of two causes as I see it - either the drivetrain is lower or the subframe is higher. The last work I did was to repair a split subframe bush. On doing this work a couple of unexpected issues popped up - one was the issues of the spacer tubes mentioned above and the other was that while basically sound there was some rust around the mounting points.

I cleaned all that up and fixed it with liquid metal. I know that's kind of a bodge but it was basically sound and I didn't have the time or the money to get it to a workshop for a load of extended welding. The net being that the position of the large washers inside the engine compartment might be a little more raised than before .... but of course that is not going to have any effect on the issues we are talking about. Might the mounting beneath the car be a little recessed into the chassis leg as a result of all this carry on - just maybe but I don't really feel like it is.

Do I feel like I tightened the whole thing (to the correct torque) more then the mounting bolts "felt" like they were when removed. Possibly a yes on that.

So in essence I feel like the subframe is sat just where it was but it just just might be a little closer to the body than it was. Maybe. It's a borderline call.

Which leaves the drivetrain. The only possibility there is sagging engine mounts or gearbox mount. I think they look ok but.........

A heap of photos follow. Would really welcome some expert opinion. At the moment I'm feeling like I'm going to end up living with it until I can afford to get a properly shaped downpipe custom made.

[olr159w]

And a few more

[Brynk]

So the Rimmer bros. stainless system ain't the best around?

Any recommendations for another stainless exhaust?? My exhaust is shot, and I would like to replace it

[olr159w]

Brynk - can I respectfully suggest you start a new thread about recommended exhausts. Tell you this though - mine has been generally great and it's only because the widened downpipe is fitted that problems arose. I did have an issue with the tailpipe some time back but it had a lifetime warranty and was duly replaced. I can't remember but I think it was made by Falcon


I'm looking for comments on the relative heights of everything and general state of the gearbox mount and engine mounts please.

[Brynk]

Okay, no problem.

I was just curious, if it was the general consensus that you problem came from the exhaust, or it was the something else that made the exhaust made the noise.

But yes you are correct, it was not my thread. Sorry

But there is some nice advice here, I wouldn never have thought about the exhaust doing it, and I didn't want to habe the same issues as you !

Carry on!

[olr159w]

Hey Brynk no problem; I just think you will get a better set of answers by posting a thread specifically on this subject.

I need to bump this thread - which I'm doing now - in the hope that someone might have a view re the state of the engine and gearbox mounts.

Thanks

[misterp]

For all of Rimmers failings with poor stuff, I`ll give them the benefit of the doubt (as you mentioned, they sell the Falcon brand) and say that it shouldn't need that amount of modification.

Those front subframe bushes look wrong (although I have not been under mine recently). It may be the amount of underseal but they dont look right.

The front subframe bushes should have a stainless tube to fix the gap between the upper and lower bush....did the kit you have come with them and are they fitted?

the SuperPro ones here Im using as a reference are here: http://www.superpro.com.au/find/superpr ... 00884/vid-

Is it a simple case of if the bushes were thicker, then this would lower the subframe in relation to the engine and give the exhaust more room?

Either way, even with a standard downpipe, I think it would struggle to get through the gap.

Is there more than one way to fit those bushes perhaps?

Double check the gearbox mount as well (from personal experience, it can make the whole car judder and shake if its fitted wrong...and to make matter worse..it fits both ways)

Just my 5c and perhaps some ideas to look at?

Cheers