Oldsmobile/Buick: Cutlass Calais error code-QDM Circuit, cutlass calais, olds cutlass

Question
I'm not sure if this question is within your expertise, but you were the expert the site offered.

I have a 1989 Olds Cutlass Calais.  It has been overheating, spitting antifreeze from the overflow, and shutting off.  We took it to be repaired and the tech told us he wasn't getting any error codes and couldn't get it to duplicate the problem when he had it.  He replaced the thermostat and then the cars computer in an effort to get a code and still couldn't get an error code or a duplication of the problem – but I still experience it when driving.  Recently a friend of ours with a different diagnostic tool hooked it up and got a reading of Volt Code 26, QDM Failure.  In my Chilton book this is showing as Quad – Driver (QDM) Circuit.  I understand that solenoids and relays are turned on and off by the PCM using the 4 drivers that make up the Quad-Drivers.  Am I to assume that all 4 drivers need to be replaced and if so, what exactly do I need to order.  Is there something else I can look at?  I look forward to your suggestions and input.  
Thank you.

Answer
Rhonda,

This question is a bit out of my expertise since it is so "computer oriented". From what I remember the ECM(Electronic Control Module)/(QDM is part of the computer itself).

You probably don't have to replace all four drivers since each controls a different system. Look through your Chilton/Haynes Manual and see if you can hunt down the driver leading to your problem .

The overheating/cooling problem might not be associated with QDM light. I've heard and read of computers being reset/cleaned and not coming up with the code anymore. This might be the reason your mechanic wasn't able to duplicate problem.

I'd spend the time and take the car to another mechanic for a second opinion. When all else fails take the car to the dealer.

Rhonda if you have any more questions please feel free to ask. Don't forget to rate my response to you.

Cheers,

Ed McKenna