Hi all, I don't come on here very often, but I've been a member since I got my 1996 850 GLT wagon over 4 years ago. I try to take good care of it--change my own oil (synthetic blend), use the good gas (93 octane), take it in for regular inspections and fluid changes, filters, etc. "The Brick" (creative name, huh?) has never given me much trouble...until now.

Coolant started leaking from the top of the radiator, where the upper hose goes in, about 2 months ago. I couldn't afford a new radiator yet so I just kept adding fluid to it as it leaked out. Then, two weeks ago, idling in park at a drive-thru window, the radiator shot out a huge amount of coolant and steam. At the same time, the temp gauge bottomed out and the engine, which usually idles around 900 RPM, shot up to over 3000 RPM although I hadn't touched the gas. I put the car in gear to limp it into a nearby parking space and the engine almost died when I did this, then shot back up to high RPMs. I parked the car, shut it off, and let it cool for about 40 minutes. Then I added coolant and tried to restart the car--it would crank but wouldn't start.

I came back 36 hours later and the car just started right up like nothing happened. All gauges normal. Computer diagonostic revealed nothing, no related/applicable trouble codes. Radiator was cracked; I scrounged up the money and had it replaced. My mechanic "drove the hell out of it" afterwards and no problems.

Over the next few days, intermittently, the temp gauge would bottom out and the engine speed would increase while I was driving--just a slight increase in the RPMs and a tendency for the engine to keep pulling when I let off the accellerator. I theorized that the engine coolant temperature (ECT) sensor was shorting out--the only thing I could think of that would explain both the gauge falling and the engine speeding up (choke, because the computer thinks the engine is cold and so sends richer mix to the engine). I ordered the sensor, it will be here tomorrow morning.

Today, the car did it again while I was driving, but the engine shot up to very high RPMs like the first time, and the engine began running rough and shaky. I pulled over and parked (just a block from work). Sure enough, a few moments later, the engine would crank, but not start. I spent 7 hours at work and came back. It started, but just barely. The poor thing sounded like it was trying to run on 3 cylinders. So I had it towed back home.

I can understand a bad coolant temp sensor being responsible for a small increase in RPMs (choke). But 3000 RPM at idle? Or sounding like it's shaking itself to pieces? That sounds more like a TP sensor (which is very expensive). What are the chances that both these sensors would go out at the same time? I am going to test the thermostat tomorrow morning when I put in the new ECT sensor on the chance that the poor thing has been overheating and couldn't tell me. If that's the case, the damage has been done.

Any ideas as to what is happening here? What else should I check? Anything I do is going to have to be DIY and cheap, because I already owe several friends that spotted me money for the radiator. Eep!