1978 911SC issues

[surfdwn]

I just picked up a nice '78 911SC. It has a few issues that I need help with:

1. The heat is stuck on all of the time on the driver's side. The temp control at the engine seems to be working just fine, opening and closing as needed. I bought new cables for the control thinking I had a broken one, but it is OK. Is there a heat shut-off with one of the "flapper" valves in the front air handling system?

2. I've had several of these cars. Every one of them had some bearing noise under load in 5th. This one will run you out of the car or at least force you to turn up the stereo. Which bearing is the culprit on these 915's? Does it need attention right away or do I need ear plugs?

3. When the outdie temp is cold, the tach is erractic. I just sold one that had the exact opposite problem, being erratic only when the outside temp was high. Any ideas?

Thanks.

David Nolen
'78 911SC

[Groesbeck Hurricane]

David,

I'm assuming you have automatic heating. Have you checked the fuses or connections around the automatic heating module? If you have manual heat and the left side control arm is all the way down then you have a broken or disconnected cable.

My 915 has zero bearing noise. Is this from the CV or the transmission itself? Is the transmission fluid old and needing to be refreshed? You might try replacing that and see if there is any improvement.

Honestly, I am clueless on where to turn on that one. But, I'm sometimes just clueless.

[surfdwn]

The car has manual heating and the engine heat/air mixture openings open and close properly. They are the same on both sides, but the heat is only on the driver's side, and it is very HOT!. I bought replacment cables, but did not put them on when I saw that the heater openings were operating correctly.

The tranny noise is definitely from the tranny, and as I stated before has been present on all of my 915 trannies, to some extent. I'm assuming it's the needle bearing on the 5th gear shaft, but am looking for suggestions before tearing into it. Don't know if good old Swepco would quiet it down or not.....

[Groesbeck Hurricane]

Have a person sit in the car and operate the manual heater controls between the seats while you watch the boxes under the car. This will let you know if the cables are operating correctly. They might have come undone or the box might have something else obstructing it. If you just want to undo it (and don't worry about mice) you could just remove the hoses after the heat exchangers. This is not a fix, but would stop the heat until you can identify what is going on with the boxes.

I know very little about transmissions (or even less than the very little I know about anything else). If I were not going to immediately address the situation, I would drain the fluid and replace with a thicker fluid and add an extra quart. It is still working on my '48 Farmall...

I wonder if the noise is the clutch plate. Do you notice it more at higher RPMs? But it is only in 5th gear? Where do you drive more than 80 or 90? I'm still in 4th until then, my wife is fond of 3rd

[surfdwn]

The noise is only in 5th, which I usually use at speeds over 50.

I think for the time being, I will disconnect the driver's side heat exchanger. I won't be needing it until at least October!

[Groesbeck Hurricane]

David,

I only use 5th at speeds over 80. What you are hearing might be "lugging" of the transmission/engine. Try staying in 3rd and 4th and see if you hear the noise. Try 5th at 75, 80, 85 and see if you still hear the noise.

[jdowty3]

Does my SC have a 5th gear? Just kidding :>) . I use 5th gear only for long ride on the highway and speeds over 100.

[Superman]

You are going too slow in fifth. My car is also a five-speed, but it could get along just fine without fifth or even fourth. Darned thing will go almost 100 mph in third, and cruises just fine on the highway in that gear. It could be a three-speed.

[goliver]

My '79 SC has bearing whine in 5th as well. Not real bad just letting you know that the majority of the miles the PO put on the clock (130K) were on the highway. Doesn't matter if you are at 2900 or 5500 it is still there. SWEPCO quieted it down a ton.

Cheers,

Geoff

[OldTee]

Re: Htr cables. Advice to watch it work is good. If you remove the parking brake control assy you will see the ss steel wire go back into the tubes to the rear. Put as much oil in the tubes as you can and if you don't have a compressor use some of that 'computer air in a can' to push it along. Try to work the control back and forth. If the wire is frozen it will bend and not move the control. On mine I could not get another control. After a period of time the oil did the trick and it now works fine. Good luck.

I think the whine in 5th was put there by the Germans to anoy the French who prefer to drink the stuff, not listen to it! It was done by the same engineering design staff, who install a water leak in every Porsche just to drive us nuts.

[surfdwn]

I think it's Swepco time for the tranny. It's either that, earplugs, or a mega stereo!

[vash]

when watching the flapper boxes, WEAR EYE PROTECTION! me, i mean i watched...err....a friend roll around the front yard trying to get the garden hose on so i could rinse my...i mean so he could turn on a hose to rinse the rust out of his eyes. he said it hurt like a mother effer! dumbass friend.

oh yea, 5th gear is for over 90 on my car. and i drive geezer like.

[surfdwn]

I found the source of the heat. Although the cable was fine, corrosion caused he heater box on the driver's side not to fully open. The spring on it did not have enough pull to open it. I manually opened it and the problem is gone! I did get a very nice pile of rust too! Later I'll have to loosen this thing up....

[vash]

yes i have a unrusty set off of a nice donor car just waiting for me to get the balls to tackle those rusty studs. glad i have mild temps here.

[MichiganMat]

I get the same bearing whine in 5, its aweful. It sounds like the tranny is blending marbles. Fresh Swepco really helped the shifting but it didn't change the noise. Ive just let it be, I don't think she's gonna quit on me anytime soon (fingers crossed). From what I've read, 915s are pretty much bullet-proof as long as you're easy on the shifter.

[surfdwn]

I have not had any of the 915's that I've had fail for this reason. It's just annoying. They do seen to eat synchros and I just finished replacing the dog teeth in 1st on an '86. The poor thing was missing about a dozen teeth and would not stay in gear!