Oil pressure and temp issues

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Greg Spreeman
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Oil pressure and temp issues

#1 Post by Greg Spreeman » Wed Jul 10, 2019 6:51 pm

I haven't driven the car in a few years but, as I recall, my temp gauge would hardly come up in temp even on a hot day. So, last weekend I finally fired up the old girl. I tweaked the spacers on the generator pulley a bit and drove to the car show, some 2 miles away. Somewhere in there, the nut that holds the generator pulley on came off. I was taking it easy so, it didn't fly all around the place and wreck my life. Got to the car show and the engine was smoking a bit. Popped the deck and the engine was really hot since the pulley half had come off. Put it back on, really torqued it on, fired up the engine and all was fine. Here is the issue, my temperature gauge never did anything. Not sure if the oil pressure gauge should have lit up but, according to the cluster, all was right with the world. Here are some pix. One is with the key turned on. Looks like the oil pressure and the parking brake are lit up. The other pix are of the temp and pressure gauges. Help?
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Greg Spreeman
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Re: Oil pressure and temp issues

#2 Post by David Jones » Wed Jul 10, 2019 7:04 pm

Greg, buy a decade box which is a way to simulate resistance and not only can you test your gauges but you may well find many other uses for it. You can buy one that will be more than adequate for most home uses from $10 or so up to $100 which would be way overkill for your purpose.
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Re: Oil pressure and temp issues

#3 Post by C J Murray » Wed Jul 10, 2019 7:14 pm

Your story is a bit odd. You only drove a total of 2 miles? Even with the belt off the engine wouldn't get very hot.

Your oil pressure light comes on about the time the engine is already destroyed, when there is no oil circulating. If you shut it off immediately you may save it but reduced pressure from overheating won't turn off the light. The oil light is fairly useless. Keep the oil level up.

As far as overheating from a belt failure, you should stop the car immediately when the generator light comes on to check the belt so that the car does not overheat. If the generator failed and lit the light without seizing then you continue on to get it repaired.

I can't imagine that a 2 mile ride would make the engine that hot.
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Greg Spreeman
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Re: Oil pressure and temp issues

#4 Post by Greg Spreeman » Wed Jul 10, 2019 8:14 pm

Good points C J. I think I must have had it idling in my driveway for about 10 minutes before I left so, tack on a bit there. When I got to the show, it wasn't on fire hot but, I definitely had to get the big nut and the spacers on quickly since they were were really hot to the touch. Kind of like when I run hot water in the sink and stick my hands under the running water.

Thanks for the clarification on the oil pressure light. It sounds like the Porsche equivalent of, call Maurice at Stoddards and get your credit card ready.

You know, I don't know that the generator light even came on. Like I said, looking at the cluster, all was right with the world. I guess my first quest is to figure out why my temp gauge isn't doing anything. I think it comes up just a tiny bit when I start the car but, in this case, I would have expected some real movement. A few years ago I did have it tweaked by Hollywood, or the other company, to put numbers on the gauge.
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Re: Oil pressure and temp issues

#5 Post by Greg Spreeman » Wed Jul 10, 2019 8:17 pm

David, I have a multimeter. It's a Klein 300MM. Seems to work okay.
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Re: Oil pressure and temp issues

#6 Post by David Jones » Wed Jul 10, 2019 8:40 pm

Multimeter is only good for measuring. You cannot simulate the oil temp sender or gas gauge with it. You can measure the sender resistance at different temps then mark the gauge accordingly. I think 200*F should register around the middle of the gauge. If using conventional oil a temp of 225 would be as high a I would want to run it. 250 and conventional oil starts to break down and will smell burnt if you run it for more than 30 minutes at that temp.
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Re: Oil pressure and temp issues

#7 Post by Doug McDonnell » Wed Jul 10, 2019 9:01 pm

It looks to me like your generator light isn't working. And unless you are out of gas your gas gauge isn't working either.
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Re: Oil pressure and temp issues

#8 Post by Greg Spreeman » Wed Jul 10, 2019 9:05 pm

Could be that I pulled the ground wire to the gauge when I pulled it out to verify the wiring. Will ground it again and see what happens.
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Re: Oil pressure and temp issues

#9 Post by Dick Weiss » Wed Jul 10, 2019 9:32 pm

Greg,

I'll agree somewhat that the engine may not get that hot as you say, but 'tweeking' the pulley shims? Why?
There should be a total of 10 and the belt-tension can be depressed around 1/2-3/4"; make sure the pulley 1/2s haven't cracked in their flat-sided holes and the 1/2s didn't get warped!

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Re: Oil pressure and temp issues

#10 Post by Dick Weiss » Wed Jul 10, 2019 9:39 pm

BTway Greg,

The oil pressure light will/should come on @ low pressure--around 3-5psi; Generator light comes on instantly
W/belt breaks or when the generator stops from belt slippage.

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Re: Oil pressure and temp issues

#11 Post by Greg Spreeman » Wed Jul 10, 2019 9:40 pm

I ordered a new pulley from Stoddard and installed it with the same shim arrangement but, it turned out to be too loose. Even revving the engine the generator light was reluctant to go out. I am guessing they might have changed the spec a bit? Also notice, I had to put an additional shim between the back pulley half and the generator body to keep it from scraping the generator.
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Re: Oil pressure and temp issues

#12 Post by Al Zim » Thu Jul 11, 2019 5:12 pm

you have two oil things that I have never seen before on a 356 from the factory. The first is a T-5 car or later with an oil temperature gauge that has numbers. That situation stopped with the 1958 T-1 cars. Second and what is causing your problems is that the oil temperature sending unit has a black insulator for the attachment of the wire to the gauge. I have never seen a black insulator with a screw on knob!! VERY UNUSUAL I suspect that this is off a later 12 volt car but not necessarily a Porsche. The resistance in the sending unit is not compatible with the gauge. SITUATION #2 you do not have enough shims on the generator pulley. When the nut is tight on the fan belt the flat of the nut must be flush with the end of the threads that it is bolted to. What you are doing is tightening the nut against the device that holds the pulleys and the shims. Zim's sells a screwdriver that makes it easy to hold the inside pulley as you tighten the nut. al zim
 

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Re: Oil pressure and temp issues

#13 Post by Geoff Fleming » Thu Jul 11, 2019 5:28 pm

Greg,
I located another temperature sender, so stop by and you can substitute this for the one you have...see if there is any change.
regards, Geoff

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Re: Oil pressure and temp issues

#14 Post by Greg Spreeman » Thu Jul 11, 2019 5:34 pm

Very impressive Al. But, before I go on, I spoke with Richard Koplin who is now 73 and he mentioned having used your shop for his drivers and his racer. The way I found him was, his family was the owner of our home from 1944 though 1994. Said that Lake Underwood was his mentor and that Lake would frequent our/his house back in the day. In any case...
The temp gauge was redone by North Hollywood who took my original and dropped in the number scale.
Black insulator on the temp sending unit...Oh, oh, time to call Stoddard for a 6V, (just saw a response from Geoff Fleming in the interim)
Pulley....wondered why I had some shims floating around in my toolbox.

Thanks!
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Re: Oil pressure and temp issues

#15 Post by Greg Spreeman » Thu Jul 11, 2019 6:13 pm

I did find this in my tool bag. Good?
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