Anyone else had this issue?
Posted: Thu Apr 18, 2024 4:14 pm
I have a 73T with a stock 3.2 engine and Sports 915 box.
Everything works, engine strong, box good as it was rebuilt a few years ago, so the power train is good.
On the road, and for several years there is a very general 'gruffness' as you go down the road at reasonable speeds.
Of course, I cannot describe the sounds well enough, but the noises/grumbles do sound like they are in a cardboard box, nothing like a roll bar touching the gearbox mounting plate etc.
So, off with the wheels today to see if there is anything obvious.
Checked:
CV joints (4) and there is very very little play, maybe 0.5mm at the gearbox flange with the handbrake on, on both sides. Shafts float well and equal freedom. Thus, i do not think it is the CV(s) rumbling.
No CV clicking turning etc at slow parking speeds. They were all replaced about 6 years/ 3K miles ago. All cap head bolts tight.
Wheel bearings. The car has the later model aluminium rear arms and the bearing play is ZERO, both rock solid and noise-free. Thus not them grumbling either.
Checked all parts for clearances, everything that could touch has at least a 15mm clearance.
Now, the possible root of the matter, and the reason for this post:
Both heat exchangers are old SSi but i think made by Dansk. They are both a good 20 years old and came of a well used rally car. Both are a bit beaten by stone damage.
The silencer is very old, about 30 years, maybe 35 and is a 'works' 'Liestrikt' (sp) 3 outlet sports job that really should be replaced for the next MoT but is not holed. It is a good silence for the road when all working as a 2 in/1 out.
The OS heat exchanger is good but on tapping it with my hand sounds as if something is loose (close?) in the casing. There is NO play in the case-to-pipes, this rattle seems more obvious in the box leading up to the heater control box.
The NS exchanger does not have the same 'sound' when hit by hand, but sound hollow as would be expected.
All bolts etc of the exchangers to the engine are sound and no cracks.
To the best of my knowledge, there are no baffles inside the SSI exchangers.
Anyone else had similar issues of noise/harshness and reasoned it is the exchanger?
Everything works, engine strong, box good as it was rebuilt a few years ago, so the power train is good.
On the road, and for several years there is a very general 'gruffness' as you go down the road at reasonable speeds.
Of course, I cannot describe the sounds well enough, but the noises/grumbles do sound like they are in a cardboard box, nothing like a roll bar touching the gearbox mounting plate etc.
So, off with the wheels today to see if there is anything obvious.
Checked:
CV joints (4) and there is very very little play, maybe 0.5mm at the gearbox flange with the handbrake on, on both sides. Shafts float well and equal freedom. Thus, i do not think it is the CV(s) rumbling.
No CV clicking turning etc at slow parking speeds. They were all replaced about 6 years/ 3K miles ago. All cap head bolts tight.
Wheel bearings. The car has the later model aluminium rear arms and the bearing play is ZERO, both rock solid and noise-free. Thus not them grumbling either.
Checked all parts for clearances, everything that could touch has at least a 15mm clearance.
Now, the possible root of the matter, and the reason for this post:
Both heat exchangers are old SSi but i think made by Dansk. They are both a good 20 years old and came of a well used rally car. Both are a bit beaten by stone damage.
The silencer is very old, about 30 years, maybe 35 and is a 'works' 'Liestrikt' (sp) 3 outlet sports job that really should be replaced for the next MoT but is not holed. It is a good silence for the road when all working as a 2 in/1 out.
The OS heat exchanger is good but on tapping it with my hand sounds as if something is loose (close?) in the casing. There is NO play in the case-to-pipes, this rattle seems more obvious in the box leading up to the heater control box.
The NS exchanger does not have the same 'sound' when hit by hand, but sound hollow as would be expected.
All bolts etc of the exchangers to the engine are sound and no cracks.
To the best of my knowledge, there are no baffles inside the SSI exchangers.
Anyone else had similar issues of noise/harshness and reasoned it is the exchanger?
