Hi guys!

I' d be most grateful for your experience and wisdom in respect of a recent occurrence:

on my 1995 928GTS the temperature gauge needle normally sits (when fully warmed up) just below the 3rd line from the left (which I take is 90F) but on three separate occasions now, while sitting in traffic, the needle has gone down below the center line and back up again (about 2-3 times) and then back to its usual. The coolant in the overflow tank is just at or immediately below the correct line (have topped it up with VW coolant only(no water) about a finger over a period of 6 months). The outdoor temperature here was somewhere between 70-80 degrees. Anything to worry about?

Thank you for any input.

Gene

 

It fluctuates 2-3 times per occasion? Do the fans turn on at the same time or do they run already? Btw 2nd mark is 80 C (176 F) and 3rd mark is 90 C (194 F).

 

I would check your connector to the temperature sensor on the bottom front of the radiator on the RHS when you are standing at the front of the car looking into the engine bay.

It is a real PIA to get at, however, it is prone to elements as it sits just adjacent to the lower front inlet air grill.

I found that the rubber boot on the female plug on my car had split and need repair. The connector is the standard Bosch two pin type and the plug is held in by the rectangular spring wire retainer.

Remove the wire spring with a small screwdriver tang or the special tool as described in the WSM, pull the plug and inspect the male and female pins for cleaniness. If discoloured or dirty clean them up and reassemble plug into connector using dialectic grease to prevent water ingress in the future. Insure you reinstall the spring rectangular clip.

Tails 1990 928S4 Auto

 

Check to make sure there are no minor leaks causing air to get in system. Is thermostat working properly ? Monitor engine temp with an infrared gauge and compare to vehicle gauge. Best place to check temp is in the coolant temp sending area in coolant crossover. If fans are on when temp rises and shut off when temp comes down fan switch in radiator and related circuit is ok.

 

Ok so the temp reading DROPS when sitting in traffic ?? If that occurs quickly I suspect a faulty temp gauge. The digital dash sometimes has issues. There are very few things which would cause an engine at normal operating temperature to quickly cool.....like none which comes to mind short of sticking a garden hose into a radiator hose at full blast I would be questioning the reading.

 

When the temp gauge dips, what is your outside temp guage saying? If it also changes dramatically then check the connections under the pod. Had this happen on my 93. Cleaning the connections with a pencil eraser 2 years ago and it's never repeated.

 

Jim is right check the connections on hte pod and clean all contacts with a white pencil eraser. Schocki's recommendation WYAIT: Re-solder all contacts on the gauges and replace all light bulbs. Talk to Rog100 he should have a source for the bulbs. They are standard instrument lights in Audis and other european brands.

How to take it off and bulb specification: https://rennlist.com/forums/showthre...ht=pod+removal

The arrow on the back of my oil pressure gauge points to the re-soldered ground connection.

 

Thank you for the input everyone. Things have been getting interesting: it has now emerged that the radiator cap may be sticking (will change this on Tuesday - holiday here tomorrow ) and, more importantly, the electric fan on the rhs, as one is facing the car, is not running . The fan is ok as it runs when powered directly, but the wire that should be delivering the power has none! Could it be the wire, could be the fan control, or what? Any ideas? Thanks in advance.

Gene

 

Did you find out what the cause is?


My '95 GTS temperature gauge started showing a cooler(?) temperature while I was on a high speed Fun Runn at 60-90 mph.

Gauge normally shows 175 degrees but it would drop down to (and stay at for a minute or two) 140, 130, 120, and once or twice into the white zone. The temperature never exceeded 180 (best guess on this "precision" dial). Fans ran normally (at least, I didn't notice otherwise). The expansion tank was about 1/2 inch over the mid-line at that time. In the morning it was just below the mid-line. There was no visible sign of leakage (steam, etc). Engine ran fine, good acceleration, etc.

 

Not really sure about having found or not the cause but had to replace the fan control box so both fans now run and the temperature seems to be holding steady but just a hair higher!