The 'E' Type Forum

Why would it be that the drivers side transmission tunnel inside the car gets so much hotter than the passenger side?

I have recently fitted the 2 missing exhaust heat shields underneath the car. The ones in the middle, expecting a big difference in the cabin temperature. This has certainly helped in reducing the temperature, but for some reason there's a huge difference in surface temperature of the transmission tunnel.

The car only has a layer of foam and a cheap thin carpet on top of this, so no effective sound or heat insulation at all. Both sides of the car are equally covered. Plan is to fit Koolmat and quality carpet this winter.

I've checked underneath the car and all exhaust pipes are symmetrically routed, so no obvious sign to me why there's this big difference in temperature between left and right side.

Dear Marcus,

Your first step ought to be to work out whether the temperature variation is coming from the engine or from air/water circulation.

The fresh air vents on the v12 marked "PULL AIR", if present, are not fed quite symmetrically - the LH side shares its air with the heater snail shell, which is missing from the RH side.

Pulling the RH of the twin heater pull switches will shut off the heater matrix (hot) water flow and will be good for about 3'C of temperature on the LH water rail.

There is always the possibility that one side of the V is running much leaner than the other side or that the cams are badly mistimed. Neither is particularly likely.

There may simply be a good reason why the airflow around the gearbox/back of the engine is uneven.

EDIT - I forgot - you don't have the heater matrix connected do you because your car has no heater box?

kind regards
Marek

Thanks for the advice Marek.

Yes you are correct in that I don't have a heater matrix. So this cannot be the cause.

It's possible that the right side is running leaner as I have been fiddling with the mixtures and am not convinced they are correctly set yet. However, could this really make such a big difference on the surface temperature of the transmission tunnel? I'll pull the plugs and check the deposits on them to compare left/right sides.

Like I said, I've been underneath the car and fitted the middle heat shields and can see no noticeable irregularity with the flow of the exhaust pipes.

I can understand if both sides of the inside of the car were hot, but equal in temperature. But this variation in temperature baffles me. I think I need a closer inspection underneath agin, perhaps on a ramp, as there has to be something fairly obvious.

Thanks again.

Even a cheapo non contact thermometer (check that it has a high enough range) pointed at mirrored positions of the exhaust manifold will quickly reveal a significant temperature difference at the manifolds.

Andrew

Will try it Andrew, thanks.

Define 'driver's side please.

Are both fans turning? I *think* they are series-wound and impossible to spin backwards but check that too. I doubt it's either.

With your non-contact thermometer check the right and left footwells from the engine side. I could envisage scenarios where there is little temp difference but more of it is reaching the interior on one side, giving the sensation of higher temp when it is merely higher ingress. The footwell vents and hoses unique to the S3.would be prime suspects, especially as the duct hoses are not super tough and could be slightly unwound or detached out of sight at the footwell spigot which isn't all that deep from memory.

I assume all undershields and the fibrous hard bell housing / tunnel insulation pieces are present? A V12.should not get uncomfortablly hot on the tunnel with all factory padding and shields etc in place so my guess is something's missing and sitting longer and closer on the driver side may just highlight a subtle inadequacy compared to standard spec.

Have you ruled out a manifold leak on the drivers side?

Steve

Make sure that all blanking grommets, plates and seals are in place. Did this job a year ago and it transformed the car - no coolmat used either.

Thank you Peter, Steve and Angus.
Driver's side is right hand side.
Yes both fans turning in correct direction.
All heat shields present and correct as are blanking plates, grommets etc.
Purchased laser thermometer, so will be able to investigate possible temp difference between left and right side of engine.
Unsure if I have a manifold leak, but should know next time the car is taken out.
Thanks again for your advice.

PeterCrespin wrote:Define 'driver's side please.

(some very dry humour on it's way....)

It's the side with the steering wheel and the pedals :D

David Oslo wrote:

PeterCrespin wrote:Define 'driver's side please.

(some very dry humour on it's way....)

It's the side with the steering wheel and the pedals :D

I'll buy that! :-)

Always happy to hear the word 'dry' and E-type footwells in the same context.

David Oslo wrote:

PeterCrespin wrote:Define 'driver's side please.

(some very dry humour on it's way....)

It's the side with the steering wheel and the pedals :D

Not always, you have never driven with my wife who sits on the side without the steering wheel.

Ps. Only joking Dear, just in case of the very unlikely event she may read anything to do with cars.

I have some interesting results regarding the issue of high cabin temperature in my V12 2+2.

The problem I had and still have, is the temperature difference between the left and right side of the transmission tunnel inside the car in the vicinity of where one would rest one's inside leg.

So on my RHD car my left leg would be against the tunnel. This is the very hot side.

Having bought an infrared thermometer, I took the car out for a drive today and was able to measure the surface temps of the transmission tunnel on both sides.

The drivers side measured 55c whilst the memsahib's recorded only 32c. A noticeable difference!

So back home with the engine running, I crawled underneath and measured the temps of both exhaust manifolds, right up the front where they go from exiting the engine to bend rearwards. So just about on this bend.

Passenger side 195c and drivers side 238c!

So I guess this is the cause of the problem. A large difference in the exhaust gas temp resulting in the different temps between left and right side of car inside.

However, I do believe the airflow and mixtures are set correctly. In fact I have spent the last few hours adjusting the airflow on each carb in turn and then balancing each bank of carbs. They were more or less evenly set. I have also tuned the mixture on the rear right hand carb as it was quite rich, and so this has been leaned off even more.

Looking at the plugs, they seem about the right colour now, as opposed to some months ago when they were very sooty.

Whilst underneath the car with engine running, I could not detect any manifold leaks at all.

So at present I'm stuck on this problem and not sure what else to do.

Any help appreciated. Thanks.

BTW. All heat shields, plugs and grommets present and correct.

So the passenger side camshaft may be advanced relative to the driver side. Sadly you can only eliminate or confirm that by pulling the cam covers off. It'd be nice to scamble under a few more v12 engines and see how they compare.

kind regards
Marek

OK Marek, thank you for this.
BTW. Is your car on the road yet?

Dear Marcus,

That was only one suggestion. If you were to have exhaust gas temperatures varying by only 25'C per cylinder, you'd be doing very well. To a large degree, whqt it does at idlew isn't that important - it's what it does under load that you'd want to really know about.

My car has been on the road for several years now.

kind regards
Marek