Running Hot...or not?

[pjs77]

I do more reading on here than posting but here goes.

After many hours, dollars and replacement parts I can't seem to get that temp gauge to come down. The back story is this:

Purchased the car last October and the temp gauge was always steady as a rock just a hair above the first white line. FF to march when I had a Porsche Shop do my belts and WP among many other things. I noticed right away that the needle was jumpy a bit and I wasn't too concerned. FF again to now and my temp gauge always reads at the third line. This has been for the last month or so. This is what I have done in an attempt to correct this:

Pressure tested tank cap and vented system about 1000 times, not seeing any bubbles
New Thermostat OEM 80C
New Thermo fan switch (lower temp than before)
New coolant hoses & heater Hoses
New HCV
New Temp Sender (the gauge one, not the DME one)
New Coolant
Cleaned MOST of my grounds (LF headlight, block, bellhousing, under drivers side dash)
Cleaned the threads to the sender and the mounting point for clean ground contact
Rewired the Temp sender with new contacts
Removed gauge cluster and cleaned the contacts per the tech write up on here

Each time I cleaned a ground the needle dropped a hair, but after doing the cluster the reading is back up but my fuel gauge is now (FINALLY) correct, it reads full, never has before in the 8000 miles I have driven it. Venting the system has no effect on this.

Initially after all the new parts I figured it had to be the grounds or air in the system as I think both of those will cause either an abnormally high reading or a jump needle. Now I am down to either the gauge itself, cleaning ALL grounds on the whole car or more venting (IDK maybe I am doing it wrong) When I vent I have tried the turkey baster method, I have tried "burping" while hot, I have tried the owners manual method and I have used a full blown pressure tester.

I'm at a loss. Why would a perfectly working combo gauge go bad? The car is stored inside, never driven in the rain or snow. Alternatively I could install a separate stand alone water temp gauge or go buy one of those thermal scanners at auto zone for $60... and shoot the top hose.

I'd like to shoot this thing right about now, with 12 a gauge Mossberg

[pjs77]

I may have answered my own question...maybe some of you would like to confirm my suspicion of the gauge.

I just picked up a thermo scanner and this is what I found:

This reading is just after I turned the car off. While running it was hovering around 83C...IMHO the needle should read a hair above the second line on the dash gauge, correct? It doesn't... it reads just below the 3rd mark. It should be noted that the thermostat I installed is a OEM 80C unit which replaced a 70C unit by the same manufacturer.



This is what the temp gauge actually means in C. According to this my gauge is always reading in the high 95-105 range give or take a few degrees.

[Rasta Monsta]

Yep, our gauges are flaky. Check the wiring to the sender, and clean up all your grounds (under the dash, at the motor, and from the motor to the firewall).

[9FF]

As Rasta said it probably the guage, or more precisely the wiring connectors to the guage. Clean up the main connectors to the inst panel and all the grounds in the footwell.

Not related to your problem but did you change your thermofan switch when you went to an 80 thermostat. They are matched, a 71 thermo goes with a 75 switch and an 80 thermo takes an 85 switch.

[pjs77]

Yes and Yes. I did all of the above. matched the stat and the switch, I cleaned my grounds twice and I have already re-wired the sender when I replaced it. I also cleaned the socket for the sender to make sure I had good ground there. I removed the gauge cluster and cleaned the contacts for the gauges as well.

I'm either going to swap in a used gauge (not too confident in that) or install a stand alone.

[9FF]

It has to be the guage as you know the temp at the engine by the sensor is reading lower than the guage. The wiring must be good as generally a loose connection or bad ground will give you a higher resistance which will cause the guage to read lower not higher.

There is a test for the guage on Clarks, I would run that test and see if your guage is reading consistently higher throughout the range. If it is you can always carefully remove the needle and reset it to read correctly. Alternatively send it to a vdo service center or buy a new guage. Not much else you can do.

Personally if I knew for certain that my guage was reading consistently high and that the temp was actually ok, I would live with it.

[ballysdad]

Does anyone on the board have a vw 1301 tool that they will rent out? I cannot find anyone who is selling one.

Guage and Instrument Testing with Special Tool VW 1301

[kfray]

A resistor substitution box should work.
Amazon.com: Elenco 1% 1 Watt Resistor Substitution Box: Toys & Games

[Sirius Driver]

also, if you're missing the batwing, it will not suck air through the rad wth effiency, but it's obviously electrical.

[pjs77]

I rigged up a separate temp gauge and it was hot. checked resistance on the regular sender and it matched the gauge through the full range, so it's not the gauge

I also checked the WP shaft for slippage and it's not slipping. I seriously have don everything you can do. At this point I need to let it go, it gets up close to that 3rd line on a consistent basis but not over. Now that my grounds are clean (and my fuel gauge reads full!!!) the gauge doesn't jump any more. I'm not loosing coolant, my fans are coming on, it's within "safe operating range" so I just need to live with it and keep a close eye. It's all i can do. Thanks for all your input on this guys.

[pjs77]

Originally Posted by Sirius Driver

also, if you're missing the batwing, it will not suck air through the rad wth effiency, but it's obviously electrical.

It's an N/A, they have batwings? And that wouldn't explain why it used to run cooler. If I do anything else it will be to install a 71C thermostat.

[pjs77]

Does anyone know what kind of effect the A/C condenser has on the system? As in air flow? If the condenser fins are bent and full of debris, would that prevent air from getting to the radiator?

I"m trying to find a comfort zone with this thing and it just bothers the heck out of me. The thought of taking this car tot the track or to AutoX is pretty scary. If I am running this warm on cool November days in the NE, I can't imagine what this thing would be doing in Boston traffic in mid July.

Any help would be greatly appreciated.

[9FF]

Point you thermo at the thermostat housing. Does it open at 80? The upper hose will get hot when it opens. What is the guage switch and guage reading at that point?

Point your thermo at the fan switch. Does it activate at 85? The fans will run when it activates. What is the guage switch and guage reading at that point?

Do the fans work as they should? One should come on full with the a/c on. With the a/c off both depend on temp and will be on half or full depending on temp. Check Clarks for exact operation.

I understand your concern and would like to see this resolved. I think this step-by-step diagnostic of what's actually going on will help and help you clear this up.

[pjs77]

Nice, I'll try that with the IR scanner on the WP and thermo switch. Didn't think of that.

The fans kick on but not until the gauge reads at the 3rd line, probably about 97C, its an 85C switch.

EDIT: fans are working as they should, it's just not cooling.

[pjs77]

Originally Posted by 9FF

Point you thermo at the thermostat housing. Does it open at 80? The upper hose will get hot when it opens. What is the guage switch and guage reading at that point?

Point your thermo at the fan switch. Does it activate at 85? The fans will run when it activates. What is the guage switch and guage reading at that point?

Do the fans work as they should? One should come on full with the a/c on. With the a/c off both depend on temp and will be on half or full depending on temp. Check Clarks for exact operation.

I understand your concern and would like to see this resolved. I think this step-by-step diagnostic of what's actually going on will help and help you clear this up.

I apologize in advance for the long entry here but I like to be thorough. Here is an interesting tid bit. I tested the old 71C thermo stat per clarks:

"Place the container on a heat source and heat the water until it reaches the temperature stamped on the thermostat. When this temperature is reached, the thermostat should be fully open."

When did the test it didn't start to open until 75C I let it go to 80C and it was maybe 1/2 open.

"Remove the container from the heat source and allow it to cool. The thermostat should be fully closed when the temperature decreases to approximately 10 degrees below the rated temperature."

Upon cooling when the water temp was about 72C the tstat was barely open, juuuuuust barely. At 68-70C it was fully closed!! I could see black gunk type build up in a small spot on the tstat, we know the old one was bad. Maybe the new one is bad too (defective)?

Like you said, I used my IR thermometer and scanned the top radiator hose when the fans came on and then the lower hose. I went back and forth probably 5-7 times and I was getting a range of temps

Top hose was reading 102-115F (Surface temp of the hose near the clamp.)
Bottom hose was reading 87-95F (again surface temp of the top of the hose coming out of the rad into the WP, oddly enough the bottom of the hose wasn't even in the ball park)

Both readings were with the fans on. I'm really have no idea if this is a sufficient drop or not. I'm also not sure if this is the most effective way to measure this. In the end I saw a max temp of 103F on the bottom hose and it appeared to drop to the high 80's.

Radiator? Thermostat? Both? Something else? It can't be something else, I mean what in the world would cause this thing to run at 3/4 and NEVER come down. Fans are working as they should, it's just not cooling and I can feel plenty of air being pulled through the condenser.

[s14kev]

I had similar questions earlier in the year about my 951. I found the top coolant neck to be consistently 90 degrees celcius with an IR temp gun. I assume you mean 102-115 degrees CELCIUS and not F. If so this does seem rather hot considering the boiling point of water without any ethylene glycol is 100 degrees C.

Running hot - IR temp gun readings - Rennlist Discussion Forums

[pjs77]

No actually. I must have a crappy IR gun. IDK why but I was measuring in F. There seems to be quite a lot of temp loss on the hoses. So those were hose surface temps, not actual coolant temps. All I wanted was to determine the difference of inlet and out let temps at fan start up and after they had been on for a while so I could eliminate the new Tstat as a culprit. I think this accomplished that (fingers crossed!!).

In any case I don't think that is sufficient cooling. The car never overheats but it never gets cool either. Fans work as they should and air is passing through the condenser and radiator. I think it's time for a new radiator. Flushing does not get rid of the oxidation and build up on the walls of these radiators in our cars. This is probably a very good example of why phosphate free & distilled water is a good idea. I plan on cracking open this radiator once I get the new one.

[s14kev]

115 degrees F is 46 degrees C. That is barely lukewarm. Upper rad hoses and coolant neck should be close to gauge temp since the factory temp sender is close to the coolant neck. I think you need a raytek or fluke IR gun.

[pjs77]

Originally Posted by s14kev

115 degrees F is 46 degrees C. That is barely lukewarm. Upper rad hoses and coolant neck should be close to gauge temp since the factory temp sender is close to the coolant neck. I think you need a raytek or fluke IR gun.

right, but it still gave me what I wanted. The two hose temps are too close for the rad to be working correctly. My money on the radiator, ordering one now!

[pjs77]

Bump...

Tail between my legs...new radiator did not fix this. I have a pressure tester and the tank cap pumped up to 15 PSI and it's back at zero in about 5 min. Not sure it would cause the car to run steady at 3/4. I would think it would eventually over heat which it never does.

I must be up to at least $600 or $700 on this damn issue...

My old tstat is a 71C unit and is closed at 70C and not fully open until 95C...just about the same temp the car is running at now with the 80C. I put the same size spacer in the car as the one that came out. Inlet side of radiator is warm, outlet side cold, bottom hose cold. Sounds like a tstat doesn't it? How can I test it while the car is running? I have a cheap IR thermometer.