Check Engine Soon Light (CESL)?

I've got an '86 Chevy Astro. My check engine light came on several days ago. I first checked the coolant to find a rusty froath in the throat of the radiator. There was still about a gallon and a half of coolant in the system when drained. I flushed the system out and swapped the radiator out with one known to be good and clean. After about 60 miles the same thing happened. When I got home I flushed it several more times this time using Cascade Dishwashing Detergent. This did clean out the system very well but I'm still getting a CESL and now it runs rough when the light comes on. Any suggestions as to what to look for first?

Check and see what the code is and post back code no.
You can jumper pins A @ B on the diagnostic connecter and get codes.
MT

I don't know if this had anything to do with it, but I noticed the waterpump leaking so I R&R'd it. CESL hasn't come on since. It has been coming on with in three miles of cranking. Knock wood:banghead:

I don't know if this had anything to do with it, but I noticed the waterpump leaking so I R&R'd it. CESL hasn't come on since. It has been coming on with in three miles of cranking. Knock wood:banghead:

Thanks for posting back and letting us know how it went.
You may have it fixed.
If it does come back on check codes and get the code no and go from there.
MT

Yeah, I will. I hope it won't. I was going to change my idiot lights over to guages from a '90 model but the speedo's are different (electric vs cable). I hope that a CESL would be rigged to come on BEFORE a "you've lost all your coolant light." But I wouldn't count on that. I'm old school. Guages are better than lights. Points and condensors are more dependable than EI's. (See my marine ?) Yeah you gotta change 'em from time to time but I know I'm going to get from Point "A" to "B" and back to "A" with "P&C" just as long as I have something to get the cap off and regap the points. I suppose it comes down to wheather you want dependbility or efficancy.

Yeah, I will. I hope it won't. I was going to change my idiot lights over to guages from a '90 model but the speedo's are different (electric vs cable). I hope that a CESL would be rigged to come on BEFORE a "you've lost all your coolant light." But I wouldn't count on that. I'm old school. Guages are better than lights. Points and condensors are more dependable than EI's. (See my marine ?) Yeah you gotta change 'em from time to time but I know I'm going to get from Point "A" to "B" and back to "A" with "P&C" just as long as I have something to get the cap off and regap the points. I suppose it comes down to wheather you want dependbility or efficancy.

You need to remember on a coolant tempture sending unit it will not work unless there is coolant on the end of it.:grinyes: :lol:
The engine can be bone dry on coolant and 350 degrees but tempt gauge will not work unless coolant on the end of it.
MT

You need to remember on a coolant tempture sending unit it will not work unless there is coolant on the end of it.:grinyes: :lol:
The engine can be bone dry on coolant and 350 degrees but tempt gauge will not work unless coolant on the end of it.
MT

Yep! Seen that many a time when I was working on cars for a living. Another good reason to have a guage. At some point it has to show an anomoly. I'd rather have a bell or buzzer than a light.

The ECM won't know the coolant is low. It really doesn't monitor that much on an '86. It only watches coolant temperature, manifold pressure (vacuum), throttle angle, RPMs, and how much free oxygen is in the exhaust stream. That's pretty simple. If you have an auto trans, it might even look at the switch in the trans to see when it's in fourth gear. That's about it.

There are a lot more analog devices on a "non-computer" system to operate the engine and it's systems. The old systems need two TVSs, a bunch of vacuum lines, and a couple check valves just to operate the EVAP canister. That's done with one solenoid by the ECM. It takes another TVS, more vacuum hose, springs, cam weights, and a vacuum motor to try to control ignition timing with the old system, and it doesn't care if you're melting/pounding holes in the tops of your pistons from burning 85-octane camel urine gas. The ECM does it with two wires and a knock sensor, and won't allow you to detonate your engine to pieces.

Fuel mixture is another matter entirely, and instead of the compromise, hit-or-miss tuning that is always part of carburetion, electronic control adjusts mixture with a solenoid and oxygen sensor. I cut my teeth on Carter AFBs, ThermoQuads, Rochester 2GCs and 4MVs, Ford/Autolite 2V and 4V models, Holleys, as well as a few Webers and Solex/Bosch systems, and they did their job, and paid my way through school. They're no match for a functioning EFI system, however. Remember the old Sun 920s and 720s we used to "perfectly" tune carburetors? Guess what they used in that Mixture Analyzer instrument - An oxygen sensor. Now your car comes with one and uses it all the time, instead of having to roll a 5' x 7' console (or bigger for the 1120) up to the side and connect a load of instruments so the tune could be right during the adjustment and maybe for a few weeks later. I'm glad to be done with that.