[steve t]

friend has problem with 1986 corvette--check engine light & low coolant light come on intermittently. have replaced sensors and relays,even a new computer. problem still exists. check engine light is when engine is hot. coolant is whenever. any help would be appreciated

[docvette]

Doc here,

Heres one I had..

The Temp sender on the right head (computer feedback) Had melted wires (Thank you muffler shop..for welding my headers and harness together..)

The coolant wires would short as they vibrated around, and throw a MIL lamp (that went away with a quick cycle of the key) So you might want to look there first..

Next I'd clean and burnish the pins on the DIC plug, and be sure it seats properly.

From there the rest is "Track down " of both systems for a loose wire (or more likely , plug)

Happy & Safe Labor Day!

Doc

[38Chevy3WCoupe]

Have you pulled the codes to see what is turning on the check engine light?

As to the low coolant light, that often happens on these cars after you refill the radiator. There is usually a pocket of air left in the engine. You need to "pack" or "burp" the radiator. This is easier with two people. Start with a cool engine. Open the radiator cap and start the car. Keep an eye on the fluid level and temperature. When the thermostat opens keep the revs at about 1500, add coolant, and close the radiator cap. Don't drop the revs until the cap is closed or you might get burned by hot fluid spewing back out. You may have to do this more than once.

Good luck.

[docvette]

Doc here,

To burp the Engine, The easiest way I have found to do this, Is, Get an underrated pressure cap, (10 to 12 lbs) Fill the radiator on a slight incline after warm, (not hot, just warm) cap it off, Fill the recovery Tank to proper capacity and Run it .. It will expel air OUT of the system, while drawing coolant back to replace it..

It looks and sounds horrible..but it's the way it works..DON'T let the Tank run dry, and let it overheat!..after it no longer blows air/coolant for awhile, shut it down, let it cool, and replace with the proper cap..you should be good to go.

I not too sure this is your problem however, The Sender in the LEFT head reports back to the gauge, (Single wire) If reading air will do excursions from like 190 to 250 and back again in a few minutes on a regular basis..Something you'd see right off..

The Sender in the RIGHT head is usually the one that reports back to the Computer exclusively (Duel wire), and an excursion here would cause a MIL lamp to light and stay on ..

Keep in mind, you are dealing with two different senders..

Codes may help to isolate the area by telling you where the failure is at..(last reported working device in the loop..but it usually won't be the actual device itself. )

Doc