sstrickstein

So my 1984 928S has a weird characteristic. When I either have the sunroof or a window open, I feel heat pouring out of the gaps in the center console. It is as if the engine heat is being drawn up through the floor. I know there is supposed to be a foam block under the floor that sits atop the torque tube. Is this the only seal? Does anyone have ideas how to stop this? If my block is crumbly, what do you guys think about that foam insulation in a can? Is my car simply missing some other part I do not know about? Suggestions are appreciated.

dr bob

Worn/sagged engine and/or transmission mounts cause the torque tube to sit lower in the tunnel. The foam insulating block that seals the console and shifter area drops with it, allowing air to be drawn from under the car through the shifter area. With windows and/or sunroof open, more hot air is drawn into the cabin due to the Venturi effect of the air blowing past the openings.

Simple fix... new motor mounts and trans mounts.

FLYVMO

There should be a rubber boot that covers the hole in the transmission tunnel and slides over the shift lever. There should also be foam underneath the shifter frame. If the engine and transmission mounts are worn, the entire drivetrain will sag down which will allow heat to enter where the torque tube foam block no longer seals tightly. Later cars (87-up) have exhaust heat shields (under the car) with extended sides to reduce heat in the transmission tunnel.

Dr. Bob types faster than me

Cheers!
Carl

sstrickstein

I should ad car is an automatic

Rob Edwards

Old rubber mounts do not discriminate between 5-speed and automatic, though the foam block differs between 5-speed and automatic- There are two pieces to the automatic's foam. But R&R'ing it will involve dropping the torque tube a bit.....

Start by checking the motor and transmssion mounts.

Dads928

this is a classic motor mount issue, engine height drops and creates a gap at the torque tube.
Check your motor mounts, ill bet they are toast

Dutch 928 fan

OMG. Such a simple question and such a 'simple' fix... Reading these type of threads assures me that 928 ownership is never the easy way...

Randy V

Sounds like you are in denial.



Replace the motor mounts.

Easy way to determine if they're shot is to lift the hood and rev the engine.

If the engine rocks back and forth they are good. If not, they are toast.

We'll all betting on the latter over the former.

Wisconsin Joe

Or just look under the car from just behind one of the front wheels. Look towards the front of the car. If the bottom of the oil pan is hanging below the crossmember, the mounts are likely shot.

sstrickstein

Does this look too low?

sstrickstein

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dr bob

Yes. If you can get your pinky in between the safety 'rebound' hooks (and obviously you can in the ones in your first frame), your mounts have collapsed. The new mounts Roger offers have those two hooks firmly engaged when installed. New factory mounts have a few mm of clearance available there.

At the rear, you should be able to get your fingers between the bottom of the differential and the top of the crossmember, up to at least your second knuckles. Less room means mounts are collapsed there too.

Tony

your recirc flap could be open in the pax footwell(even though it defaults closed..perhaps bad HVAC controller)) and the air, through what ever circulation pattern it takes in the cabin is being drawn into the HVAC system and then pulled out though the suction of the windows and sunroof.

also...
Check the rubber boot that connects the blower to the blower tunnel under the rain splash shield. If it has a gap, which it often will on the underside, it will draw in engine bay air. That boot can be a PITA to get on if the blower has been replaced in the passed and when it may look like you have it on from the top, the under side it may not be.


Also..the foam in the transmission tunnel will either be glued in place or stuck in place. Highly unlikely it is going to sag with the drop of a an inch or so with bad engine or tranny mounts. It is not physically attached to the torque tube at all...only the shift cable passes through it. My foam has 180k miles on it...wasnt even remotely "crumbly" and was stuck solidly in place when i went to remove it last month.

BTSAT (been there seen all of this)

sstrickstein

I had the car on a lift today. All my mounts are sagged but not blown. I guess I will add that to the list of to do . Thank you for the input.

dr bob

I'm not sure what "blown" means in your context. For these engine mounts, the failure mode is 'sagged' unless you get in an accident severe enough for them to shear off. Those safety rebound hooks prevent the mount from failing in tension. The trans mounts have a little V saddle with rubber blocks attaching to the mounting flange on the crossmember. When they fail, the gearbox sags down into that V saddle. So for both, 'sagged' is the same as 'failed'.