Scuttle-shake?

[gouldsborough7]

My Hunter has recently developed what I believe might be scuttle-shake, coincidentally not long after my local garage did some work on the exhaust system. Shortly after the job, I got them to check over the car, and they did some minor adjustment to a mounting-bracket to cure the rattle/booming noise occuring around 1500rpm in any gear.

The rattle/noise came back after a week or so, so I got it up on jacks, and checked underneath from front to back. No part of the exhaust was touching the chassis or any way close, but I added another bracket to be on the safe side. No real change!

Still puzzled, I took my car back to the garage, and they gave it a road-test with 2 guys in the cockpit. Their conclusion was that the noise came from beneath the dashboard - a bit puzzling as there is nothing there to make such a noise. They were correct in a way, as I could suppress some of the noise with my hand on top of the dash. I took off the vinyl top, and sandwiched rubber sealant, plus used Blue-tack (useful stuff) in various gaps. I stopped the dashboard noise/vibration at 1500rpm, but this area still booms at these revs. Either side of this figure, the car/engine is smooth and sweet as the proverbial nut.

Is this scuttle-shake? and why has it only just reared its ugly head? All a bit of a mystery! Any help would be appreciated.

Cheers
Mike

[greyV8pete]

Re: Scuttle-shake?

Hi Mike. You say you jacked the car and checked the exhaust clearance but you really need the car on its wheels as the rear suspension moves down quite a bit nearer to the exhaust then. I had the same problem with the twin pipes from my V8 and rigged a tie strip between the two pipes to pull them closer together to avoid the suspension. I know you think the noise is from the front but noise tracks in very mysterious ways in cars! Have you checked the propshaft for blobs of paint or underseal, or even a missing nut? If only a bit out of balance they create an incredible amount of vibration, not to mention gearbox bearing wear! Good hunting! Peter.

[gouldsborough7]

Re: Scuttle-shake?

Hi Peter
I omitted to say that my jacking precautions included lowering the rear wheels onto large blocks of wood. This was in addition to the 2 trolley-jacks and axle-stands (6-points holding the car in the air). So I guess that the rear of the car was effectively in running position, albeit on a slope.

I'll certainly check out your other points. Funnily enough, when I got my local village garage to check out the car, I suggested that the problem was at the rear somewhere. In my checks, I had removed all contents of the boot, and even the lockable panel between boot & seats, to no avail. I was therefore surprised and puzzled when they identified the dashboard area. My efforts in that area have stopped the individual rattles caused by poor factory assembly, but the booming still continues at 1500rpm. Even the rear-view interior mirror vibrated at these revs. I have beefed up its fitting to the windscreen, so that 'sympton' has been cured.

When I cure the vibration, I will report back to the Forum.
Thanks
Mike

[CABRIOBOB]

Re: Scuttle-shake?

I have experienced this boom noise on odd occasions on rough roads and I found it was the floor pans flexing slightly under the seat towards the peddles, if when you hear it try pushing your feet hard on the floor to see if it stops. It could be when your garage fitted the exhaust it is slightly positioned differently as before and is causing an echo resonance type noise which is travelling down the chassis like a tuning fork effect.

[Dane_Rescueman]

Re: Scuttle-shake?

I run a 2.1 pinto in a mild state of tune. It, and the previous 2.0 litre engine displayed a resonance between 1900 and 2200 rpm. I have a side exhaust though which seems to accentuate the boom. I tweaked mixture and timing which helped a tiny bit.

[gouldsborough7]

Re: Scuttle-shake?

Thanks Guys
The resonance idea would appear to fit the bill, because the dashboard area vibrated (before I did some re-jigging of the vinyl/aluminium top as mentioned earlier). Even the interior mirror (stuck to the windscreen) vibrates in sympathy! My exhaust comes out just behind the offside rear wheel.

Interestingly today, now I am thinking about the problem more & more, while the engine was warming up (and I assume running slightly on the rich side in the process), the booming/vibration was not quite so obvious.

As my Hunter is fuel injected, with twin solid-state coils/no distributor (not sure what the correct name is), there is nothing I can adjust in reality. My local garage proprietor (who is a real enthusiast for fast cars) suggested I changed the fuel-pressure regulator for an adjustable version, and tweak up the supply a bit. However, this appears to be a fairly pricey route, with no guarantee of success.

Another local garage advertises a 'electronic engine tuning' service. Not sure exactly what this might include, but might be worth me making a casual enquiry to see how detailed their service is.

Cheers
Mike

[greyV8pete]

Re: Scuttle-shake?

Hi Mike. In my previous post my brain was working back to front. When you lower the car the suspension in fact moves away from the exhaust, not towards it. However I remember now that when this happened on my car the suspension arms that were holding the exhaust down when the car was jacked up (not easy to detect as the contact points were above the trailing arm when viewed from below) released the exhaust and it moved upwards and contacted the diff housing! With the V8 at low rpm the noise was very loud so worth another check for this point.

If it is the floor panels flexing as Bob suggests try some self adhesive sound deadening pads under the carpet. You can get these at most motor factors and they really do stop panels booming. Peter.

[gouldsborough7]

Re: Scuttle-shake?

Hi Peter
On reflection, I think my problem is something to do with the engine management. The engine is inclined to hesitate within the rev range 1500-2000rpm, but sweet as the proverbial otherwise. In certain situations i.e. in a high gear going up an incline, the engine is under load and something about it is not happy. In this circumstance, if I drop a gear and make it rev a bit more, or if I am accelerating right through from a standstill, then the booming/hesitancy is not at all noticeable.

I will bear in mind all of the comments and ideas raised so far, and might chat up the local garage offering the tuning service as I mentioned above.

Cheers
Mike

[greyV8pete]

Re: Scuttle-shake?

Hi Mike. Interesting that your thoughts have gone full circle as in your previous post where you were thinking about engine management! Not being familiar with Ford injecion systems I can only offer my Rover V8 3.9i injection experience. I had a progressively worsening performance, with jerking and snatching at low revs, popping back in the exhaust on overrun and eventually an MOT fail with 8.0% CO2! As the Rover ECU chip was for a 2 ton Land Rover it was just not suitable for a car under half that weight and to a lesser extent this could be your problem. I fitted an Optimax chip from RPI which was designed for the engine and lambda sensors to tell the ECU what was happening to the exhaust gases. I also fitted a new throttle potentiometer, set up the base idle and fitted a new idle control valve. The result was to transform the car into a really flexible and driveable machine. Fuel line pressure and dirty injectors, both of which can give poor or uneven combustion should also be considered.

You may want to consider visiting someone with a rolling road, who knows about Ford engines, who can reprogramme your chip to suit the car rather than getting someone to try and "tune up" what may never be the best set up for your car? Good luck! Peter.

[gouldsborough7]

Re: Scuttle-shake?

Hi Peter
Wow, you really went to town on the tune-up stuff. Not sure I would be sufficiently brave (or knowledgeable) to tackle those changes. If I had clear instructions, then I would try.

I think I will chat up the garage I referred to above, and see what they can offer.

Cheers
Mike

[greyV8pete]

Re: Scuttle-shake?

Hi Mike. If you are painting the rear suspension does that mean that you have fixed the engine problems? Before my MOT fail for emissions I knew nothing about fuel injection. After that I spent 5 winter months trawling the internet for info and am indebted to the forums for Land Rover, MGRV8, Morgan V8 as well as the wealth of info on the RPI website.

Have a Google for some Ford owners club forums and type in your (that is your engine's) symptoms! I bet you find other like minded souls who have had and fixed the same problem(s). Peter.

[gouldsborough7]

Re: Scuttle-shake?

Hi Peter
Just caught up with your message. I haven't really cured the engine hesitation, but I am probably driving the car in such a way as to avoid the problem most of the time, i.e. keeping the revs in each gear over 1500rpm or not labouring it at lower figures.

I was tempted to consult a local garage which advertised electronic tune-ups, but wasn't sure if this service would resolve the trouble, and would more than likely trouble my wallet in the process!

I moved on to the painting job, as I had a litre of Wickes bitumen paint in stock that covers everything like magic, anticipated having some spare time, and the end-product looks reasonable as well. If it begins to look shabby in a year's time, I can redo it without too much bother this time.I have done the legwork at getting rid of the old delaminated Marlin powdered coating, so a cleanup with white spirit, and a few hours with a paint brush should suffice.

Thanks for your interest.
Mike