Suburban 3/4 Ton 4WD V8-305 5.0L (1986)
Coolant: Technical Service Bulletins
Coolant - Information on Propylene Glycol Usage
File In Section: 6 - Engine
Bulletin No.: 43-62-01B
Date: April, 1995
Subject:
Propylene Glycol Engine Coolant
Models:
1994 and Prior Passenger Cars and Trucks
This bulletin is being revised to reflect most current information on propylene glycol engine coolant. Please discard Corporate Bulletin Number
4362O1A (Group Reference 6 - Engine).
General Motors has been reviewing data supplied on the performance of propylene glycol engine coolant in GM vehicles. It is our conclusion that
propylene glycol engine coolant will perform adequately under most vehicle operating conditions. As a result, propylene glycol engine coolant (meeting
performance specification GM 1825M) may be used in GM vehicles and will not affect the warranty coverage.
Prior to adding propylene glycol engine coolant to the cooling system, all the existing (ethylene glycol) coolant must be removed. This can be
accomplished either by utilizing water-based coolant flushing equipment or "waterless quick change" equipment available in the GMDE program. As
with any coolant change procedure, be sure to thoroughly purge the heater core and block as well as the radiator before attempting to convert the system
to propylene glycol coolant.
Freeze/Boil point levels are different for propylene glycol than for ethylene glycol engine coolant. To accurately determine freeze/boil protection level, it
is imperative that coolants not be mixed. Removing all the used coolant as previously discussed resolves this concern. Freeze protection of propylene
glycol cannot be determined using a standard hydrometer. Rather, a refractometer or test strip must be used.
Propylene glycol engine coolants may be recycled in the same manner as conventional ethylene glycol coolant. No adverse effects will be encountered if
these coolants are mixed prior to recycling, however, the ratio of propylene glycol coolant to ethylene glycol coolant should be kept low to minimize the
effects on freeze point measurements.
