Hey all, I just bought a 1987 928 and LOVE it, and I'm psyched to be part of this crowd now. I've been checking out this site for months and now that I own a 928 I'm gonna get more acquainted.

So, my 928 is in good condition and I had it checked before buying, so I'm confident its gonna last, but here's my question...And I have looked at past posts that have helped me understand things better, but here it goes. After driving for a couple of minutes my temp gauge creeps up into the upper third, close to the red, and then bobs up and down and goes back to the middle, only to creep back up and bob around again. Now, driving around town it stays pretty high, but then out on the road it looks as though it's not running as hot. I know that sounds like an airflow problem, I'm just wondering about the bobbing gauge. Does that make any sense to anybody?

Thanks in advance.
Dave

 

Dave,

Your problem could be bad air flow or bad electrical grounds causing eratic gauges. Also, a bad thermostat, air in the system, low fluid in the fan clutch, bad temp switches or relay for the electric fan or a leaking head gasket could cause this problem. Are you loosing any coolant or have white smoke when the engine is warm?

Dennis

 

I would check the coolant levels and the thermostat. I just bought 928 that was having heat issues. After taking 10 minutes to replace the thermostat, it turned out that the PO just never paid attention to the coolant level. 3 jugs later and my $1500 project car turned into a $1550 driving car.

 

Lately I've gone around and around with my pod...

FIRST I installed red indiglo gauge faces...not good. In fact they were pug-ugly~

SECOND I installed red reverse indiglo gauge faces...black with red letters- it worked, especially after I painted the needles white and put the plain bulbs back in their holders so that I could see them at night. I finally have red gauge illumination that I can see when it gets dark!

THIRD I found a perfect instrument pod in a junkyard here in the land of the mouse. $40...and the rattlesnakes inside the trashed car were only 3 feet long!

TO SAY THAT I AM NOW FAMILIAR WITH THE GAUGE POD is probably an understatement. Of course...with my car's checkered maintenance history, most systems are understatements for me~

But looking at the object that seems to spend half its time on my dining room table brings me to the conclusion that like many extraneous items on Porsche's project 928...the gauge cluster was not an object of great interest to the engineers and since we are driving cars designed and built by gearheads...it didn't receive that much attention.

Which is all an eloquent way of saying that I don't think that the gauge cluster is of very great quality That and these cars are just plain old. Which means that just like the gauges in the airplanes that I fly for a living...I pay more attention to the trend than to the actual reading. You see, even with high quality gauges, there is tremendous production line variation and you can find two 928's that in reality run at the same temperatures but who's gauges read totally different.

My advice would be to take the car to a shop and ask them to hook up some sort of temperature gauge in order to find out exactly what your temps are. Since your gauges are probably working right [they are INDEED showing trends that make sense: hot in traffic, cool on the highway], I would tend to believe them. It sounds like an airflow problem to me, but might not be a problem- your temperatures may indeed be within the "green arc". How many times has an aircraft mechanic told me that the fact that the oil temperature on one of my turbofan engines running right up against the red line [but still in the green...] is ok....

Normy!
'85 S2 5 Speed

 

Dave,
Welcome to the club
As Normy said, get the real temperature controlled
If/when you check/change the thermostat, remember the rubber seat behind the thermostat
Good luck

 

Normy, can you post a picture of your new indiglo pod?

 

Since its an '87 it will have two electrical
fans......make sure both are operational and act the same relevant to each other. Sometimes one will be bad/dead and spin slower or not at all.

Then check the air intake "flaps" in front of the radiator. They should cycle through a couple of different positions in regard to the engines temp. A quick check for both this and the above item is to turn on the A/C and you should see both fans operate and the flaps should go to full open.

After these quick checks it may be good just to refresh the whole system with a new thermostat and seals along with a new temp switch for the
radiator itself. Then refill with fresh coolant and bleed air out properly. The symptoms you have could simply be air in the system!

Good luck and welcome!

 

Erik's suggestion was what worked on my 87S4 hot running problem. My gauge didn't cycle, it stayed high. Feel the temp difference between the two hoses when its hot. They should be close, mine were not. The rear t-stat seal fixed it and the gauge came down to midway and stayed there. If you buy it locally, make sure you stress that you want the seal pressed into the housing at the rear of the t-stat. Everyone tried to sell me the large O-ring. They didn't show the rear seal in their books.

 

Man, you all are awesome! Thank you so much for all the advice. I'm taking it in tomorrow to a good shop so I'll have them check the airflow and the thermostat and everything else. It looks to me like the fans aren't running at all. Also, I'm not familiar with where the thermostat is. If possible, could somebody explain to me where it is? I have yet to buy my manuals so I'm depending on the internet to figure everything out.

Thanks again!
Dave

 

I used these instructions:

<a href="http://neptune.spacebears.com/cars/stories/statstoc.html" target="_blank">http://neptune.spacebears.com/cars/stories/statstoc.html</a>

 

Dave,
My fans weren't running either. Someone can back me up or correct me on this but I think the fan sensor is located on the left (drivers) side of the radiator. On my car (87) they didn't cycle because the rear t-stat seal wasn't allowing the coolant to flow through the radiator, hence the hose temp check I mentioned earlier. On my car the lower hose was cold, upper hot. After the seal change, the coolant flowed, the hoses were similar temps and the fans cycled normally. Good Luck.