Fans are wired right

 

That is the coolant level sender. Lets you know when low on coolant.

 

For some reason the PO had bared the 2 wires for the sensor about an inch from the connector and twisted them together!! So I doubt if that was the cause.

I filled her back up with coolant and took a 1/2 hour drive. The needle bounced around at first and came close to the red line then settled back down at about the 2/3 level. Wondering if it is a sticky thermostat then. I have one on order and will replace it later this week

 

Air in the systerm?

 

what did the radiator feel like when it was over heating. if the thermostat is possibly to blame, the radiator will be cool. radiator could be clogged . probably more likely than a thermostat. air in the system could also be an issue.
mk

 

Solved - I think

Drove to work, needle bounced from mid range to high. At work, opened the hood and there was a moderate amount of coolant spewing from the expansion tank. I took a closer look - there is a crack about 3/4" long neer the filler neck and that is where the coolant is coming from - thus the system is not fully pressurized. I guess I know what I'll be doing this weekend!

I think this is the problem - thanks for all your help and suggestions - as usual

 

In the meantime, back off the expansion tank cap and run at 0 pressure - if it's not too hot locally, you can get by this way without coolant loss until R&R is possible.

 

On a related note...

has anyone collected and documented temperature measurements of a known good-cooling 928? For instance - What should the temperature at the water bridge elbow be? Temperature coming out of the rad? What's too hot? etc. Obviously ambient conditions factor in too, but any baseline data would be interesting.

I ask because I have the feeling that my '91 is running a tad hot and 928andRC51 thinks the same of his '87. However, rather than trusting the temp gauge and just making educated guesses about what might be wrong I'd like to actually know via measurement if its hot and where.

I can use my '89 and '94 for data collection... as soon as the snow melts. But, prior to that has anyone BTDT?

 

What Dave said; does anyone have real temp data of coolant out of the crossover???
We took some quick infrared temps on my car and found 210 or so, too hot.

 

I think Doug Hillary did at one point, came up with 90°C on most parts of the block IIRC. He doesn't post much so you should be able to find it pretty quickly by searching on username.

 

Ken, After my sc install I had the same problem! I made sure the fans were pulling not pushing and that was ok. I still had the problem until I added the extra fan in front. Those little ones with the kit are good, but not quite enough. The extra fan installed, I stay 1/2 to 5/8 all the time. Hope this helps!
Kevin

 

Thanks Kevin I'm now pretty sure the immediate problem is the crack in the overflow tank. I just went through some of the parts the PO gave to me when he sold the car - and low and behold, there is a brand new tank! Obviously this was a problem before, probably enhanced by the s/c, and the temporary "fix" was to short the coolant level sensor wires.
If I have time this weekend I'll pull the cooling flaps and install the aux fan.

Its beginning to get warm down here, so next on the list, as I get the reliability issues fixed, is the HVAC system - it is completely inoperable

 

Cool. I was planning to search. But, with that info it should be a lot easier.

Thanks Dave

 

The biggest factor in the entire cooling system is obviously the radiator.
If your radiator is 15 years old it proabaly works at 70% efficiency at best (maybe only at 50%). Then if you are constantly running too hot other stuff starts to fail. These old radiators get plugged up on the bottom on the outside and many passages on the inside get plugged up as well. Add some corrosion...