91 Jetta Overheats & NO Dashlights

[surfmore68]

I'm really hoping someone can provide me with guidance, because none of the mechanics I've seen have been able to help, and this is becoming pricey... Two problems:

1.) Overheating - I've changed the rad, thermostat, fan, replaced two expansion tanks and caps and even my engine recently...no dice. The heat light came on this morning on my way to work so I added water before I left the office, and by the time I got home 30 minutes later the heat light was on again. Mechanics keep telling me everything is fine...clearly everything is not fine. I don't know anything about cars so any advise that would help me to speak intellegently to a mechanic and finally get this resolved would be GREATLY appreciated.
2.) Dash lights are out - a friend tried changing numerous fuses. The only one that had any impact is the one that tells you your headlights are on. How ironic. We switched every other fuse; nada. About 4 years ago when I bought the car we replaced the car stereo with an after-market one. It works fine, as did the dash lights up until about a year or so ago....could the two still be connected?

ALL IDEAS ARE WELCOME!!!! PLEASE HELP IF YOU CAN!!! I really don't know what else to do..

[Doug Tatham]

I can see a couple possibilities. The first is that your heating sensor is bad. You have two sensors on the plastic pipe coming out from the front of your engine. One could be bad, I don't remember which goes to the temp gage and which goes to the alarm, but that's a place to start. Does your temp gage show high temp or is it just an alarm? If it's just an alarm, unplug one sensor and see if the temp gage drops to zero. If it does, then the other one is for the alarm.
The second possibility is that that circuits on the back of your dash are flaking out. Your instrument panel may need to be replaced. This could explain the dash lights as well.
Have you checked the bulbs on your dash. Have you checked the light switch. Remove the switch and test the contacts for the dimmer control with a multimeter. The resistance should change when you rotate the control in opposite directions.

[surfmore68]

Hi Doug:

Thanks for responding. I've read quite a few threads where you've replied and have been helpful to folks writing in, and I appreciate you taking the time to reply to my inquiries.

Both the temperature gage and alarm activate, however I'm not sure how high the temperature is supposed to go on the gage before it would normally trigger an alarm. On my car, it never gets past mid-point.

Would it be circuit related if the expansion tank also completely empties when this happens? RE the dash lights, I have tried testing the bulbs, which are fine, but not the switches. I'll give this a go. Thanks again.

[denisond3]

Have you found the problem yet? You have replaced most of the things I would have suspected. Do you know if your water pump is -pumping-? Its rare, but once I had a water pump where the impeller came loose from the shaft - on my old Jaguar, not on a Jetta. As my 90 Jetta lacks a cap on the top of the radiator, I dont know any quick way to measure water pump flow .
And I wonder if the 'warm-up loop' is vital for the Jetta engine to avoid overheating. That is, the hoses that let water flow around through the heater/block/head until the engine is hot enough to need the thermostat to open. If the heater were clogged or the hose kinked, would it affect the engines cooling system during warm up?
Any problem your Jetta is having might be a problem my Jetta will have someday.

[Doug Tatham]

If you're getting a temp gage reading you're probably circulating coolant. There are 3 water temp senders and one oil temp sender. All cost less than $10 online. One of the water senders turns on the aux fan, one sends a signal to the gage and I think the remaining goes to alarm. It may be the oil temp sender that gives the alarm, or it may be both.

[moparvwfreak]

they have the years wrong here for the body styles. my 90 jetta is doing the same thing. same car as your 91. there is a sensor int he coolant bottle that shows if your low on coolant. teh wireing for that has a nasty habit of corroding due to how the sensor is setup in the bottle itself. trust me. i have been wracking my brain over this for 2 years now. is the guage reading normal? are teh fans comming on??
if its working right and the warning light is the only thing comming on then its a wireing fault and thats about it. i have temporarily delt with mine by clipping a lead off the LED inside the cluster. my car does not overheat according to the gauge, fans kick on and i have not lost any coolant int he last 30k with it this way. you should be fine.

as for the dash lights they may have burnt out or the switch has gone bad. changeing them is fairly simple once you get the cluster out. my suggestion is get teh GOOD repair manual on it. its by Robert Bently Publishing 1985-1992 golf \jetta reapir manual. includes 8 valve, 16 valve and deisel engines. that will take you step by step on how to do almost any repairs on your jetta. here is a link to the book at teh publishers website. http://www.bentleypublishers.com/product.htm?code=vg92 hope this helps.

[Doug Tatham]

Whenever I buy a new car (or used car if I plan to keep it awhile) I buy the dealer service manual. They run $100 + but they are really worthwhile. You get the proper schematics for wiring, trouble shooting guides, all torque specs and they are for your exact model. The VW Jetta comes in CD version.