Introduction and Overheating (long)

[ChattanoogaJSB]

I lost all of my first lengthy post, so I'll keep this short and try and add only what's necessary. I'm sorry it makes for a less congenial introduction.


91 ZR-1 was bought new by my friends father and driven 7K miles in the first two years. Sold, found again two months ago by my friend and purchased with just about 1K miles more. he had it serviced including new green coolant (but no idea if it was truly flushed), we drove it home 2,800 miles from Oregon to Tennessee in four days. low on power, shop had done three bad secondary injectors but not tested the primaries. I found four bad primaries ohm testing the ecu plug. all injectors I have now done with Accel, which totally restored the power!



On drive in flat country car would not run over 149 mph on a "closed course" in fourth or fifth but did not overheat at cruise. First mountain pass- overheated to 7/8 gauge, when we stopped. This was only when we were pulling uphill, but only going normal speeds. Downhill and flat were fine, temps restored to normal (about 1/3 of temp gauge)



Note when it got hot the overflow was simply ambient temperature and no change of level. Overflow still never seems to move and we have tried two caps.


swapped thermostat with a NAPA unit, but new and old boil-tested fine.


Fans come on. Used registry member scottfab method to refill (thank you!) taking off throttle body coolant line on drivers side as I filled to top.



both intake hoses will run 210 degrees with the fans on idling, system seems full. coolant looks clean. As soon as you ask it to pull a grade the temps go over half to 3/4 and will eventually go to 7/8.


My thought is that the radiator is probably flowing very minimally, having sat with (the orange?) coolant in it for possibly many, many years at a time.


can anyone help give me any other ideas? should I pull the radiator and have it cleaned or can i try and clean it in place?



I'm a regular on the CF but new here- I am not afraid to work on the car but I am trying now to get a little group consensus. I've got a '64 coupe that I rebuilt after a semi truck hit me, have had a couple of 69's and bought an 09 new. I also had an Lt-1 powered 95 Firehawk.


My friend has been a lifelong Porsche fan (as was his father) and I am desperate to make his ZR-1 the "better car" I know it can be!


Thank you in advance for any advice!


Benton