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Car Forum / Volkswagen / Water Cooled Volkswagen Cars / June 200981 Scirocco suddenly overheats
Temp gauge goes to top, red light flashes, but radiator doesn't steam and fan doesn't come on. Oil temp rises slowly. Takes about 5 miles of urban driving from cold start. Started cold and allowed to idle. Took about 15 minutes for gauge to hit top and red light to flash. Oil temp between 80 and 100C. I'd removed the radiator cap before starting. Based on how a cold thermostat blocks water from radiator to coolant pump, I thought the coolant level might rise in the radiator and perhaps flow out the filler, but coolant level did not noticeably change (I did not leave the cap off while warming up). After shutting off the engine, I jiggled the connector to the fan. The fan started. Wondering "loose connection?" I started the engine again. The fan shut off. I shut down the engine again. This time I pushed a fan blade a little. Fan started and ran for a very short time. Runs strong, with the usual sound, and turns easily when cold. I did not suspect the fan because the temp still rose even when driving at 40mph. Coolant pump pulley is turning, pump has never made noticeable noise. No leaks. Venture a diagnosis, anyone? thx, nf Bad gauge? Coolant temp sensor? > Temp gauge goes to top, red light flashes, but radiator doesn't steam and > fan doesn't come on. Oil temp rises slowly. Takes about 5 miles of urban [quoted text clipped - 25 lines] > thx, > nf Could be several things: a few broken blades in the water pump; half stuck thermostat; or given the age of the car, corroded and intermittent wiring. Quite possibly several things at once. Is the radiator getting hot? Thermostat closed or blockage or water pump not pumping. Does the heater blow hot? Thermostat closed or blockage I have seen A1 radiators that were partially blocked at their bottom. I could take out the fan switch and no coolant would come out. 8^o Yes you might have wiring issues to the radiator fan so look for corroded wiring under the battery and fuse box terminals. Fuse boxes were known to have issues with the A1s after water gets to them. :-( But 5 minutes of urban driving is pretty fast unless the outside temps there are already 90+ degrees F. Might also be an engine problem along with a radiator fan issue. :-( JMHO  Signaturelater, (One out of many daves) >> Temp gauge goes to top, red light flashes, but radiator doesn't steam and >> fan doesn't come on. Oil temp rises slowly. Takes about 5 miles of urban [quoted text clipped - 35 lines] > stuck thermostat; or given the age of the car, corroded and intermittent > wiring. Quite possibly several things at once. "dave AKA vwdoc1": > Is the radiator getting hot? Nowhere near what I'd expect with gauge at the top. > Does the heater blow hot? Ah, good idea. Why didn't I think to check that?! > I have seen A1 radiators that were partially blocked at their bottom. I > could take out the fan switch and no coolant would come out. 8^o Hmm, given the strange fan behavior, that might also be worthy of a check, even if the problem is a thermostat (which has never been replaced in this car). > Yes you might have wiring issues to the radiator fan so look for corroded > wiring under the battery and fuse box terminals. What is it about Scirocco wiring? I never had such issues with my old 72 Montego or even a '68 bug. A few years ago I had a problem with not starting when hot. Turns out the wire from the ign switch to the solenoid had cracked insulation and the wire inside was almost completely eaten away! > But 5 minutes of urban driving is pretty fast Actually, I wrote "5 miles" of urban driving, ~10-15 minutes. Thanks! Thanks for the suggestions. I was wondering about the temp sensor, but since the radiator doesn't feel very hot and the engine around the sensor does, I'm thinking I better start by inspecting the thermostat (just as soon as my arm recovers from a recent 90° attitude change on my motorcycle). > Temp gauge goes to top, red light flashes, but radiator doesn't steam and > fan doesn't come on. Oil temp rises slowly. Takes about 5 miles of urban > driving from cold start. My guess...having had exact same symptom in the past with a diesel VW T25 thermostat...thermostat...thermostat T-stat is not opening, so coolant is not getting cooled. Hence cold rad, and no fan. If the fan is being sticky, not necessarily a connected issue, then you may as well change the thermoswitch at the same time. In my experience, don't bother with a generic part, go for a genuine VW t-stat and t-switch. You can test your own t-stat in your kitchen, drop it in a pot of boiling water and see if the spring gives or not. Hope this helps ;o) > thermostat...thermostat...thermostat Thanks. I'll be checking that in the next few days. |
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