I'm having some strange coolant loss that is definitely not burning in the engine. Lots being sprayed all over passenger side engine compartment. Small drip on ground and less in engine compartment on driver side. Fluid on and near heater valve. Loss of heat. Not completely but definitely decreased. I think the OEM core is finally toast. Looks like it may just be under a black case in passenger footwell. Hopefully someone has the year specific shop drawings of the heating system? Do I have to pull the whole dash? Screwtube has nothing I can find that's year specific.

1991 G20 5.7L 350ci
w/accessory rear heater

​​​​​​
W/ac

Sorry photos suck

Thanks in Advance

 

Here is one diagram. If you email me help@brokenemotions.org or oceanmeat@icloud.com I can send you the six repair manuals it took me three months to find. With these you should be able to repair your g20 on your own, or even burn it to the ground and build a new one without the problems previous owners add for you. (I too am having problems with mine &#129763

 

• 1991 GMC ELECTRICAL DIAGRAMS AND DIAGNOSIS MANUAL R/V, P TRUCK MODELS (379 pages)
• 1991 GMC light duty truck r/v, p models service manual (1593 pages)
• 1991 CHEVY ELECTRICAL DIAGRAMS AND DIAGNOSIS MANUAL C/K TRUCK MODELS (193 pages)
• 1991 CHEVY LIGHT DUTY TRUCK UNTIT REPAIR MANUAL (855 pages)
• 1991 GMC LIGHT DUTY TRUCK FUEL AND EMISSIONS SERVICE MANUAL INCLUDING DRIVEABILITY FUEL INJECTED GAS ENGINES ONLY (406 pages)
• 1988 GMC LIGHT DUTY TRUCK R, V, G, P models service manual (1576 pages)