ZR-1 Maintenance Tips

General Maintenance

by Jim VanDorn


The most common call we receive by far is from a confused ZR1 owner. After years of reading everything from which thermostat to use, to what type of spark plug is best, the average owner is totally and completely confused...and for good reason. There are many varied opinions of what is best for our cars but that may depend greatly on how you use your ZR1.


After seven years plus, many ZR1's are finally accruing some mileage. We have had the opportunity to closely inspect many engines with a variety of types of use from normal street driving to severe "weekend" use (track time). Compiling this information we can now offer the ZR1 owner some observations. One rule we've adopted after hearing so many owners say the same thing is the "DIMWIT" or "Darn, if I didn't Mess With IT" rule. In other words, if you didn't have a problem, then what are your intentions in the first place? To date, the only company known to have a fleet of engineering ZR1's to test with was GM and it's affiliates.


Therefore, we must ask ourselves if their suggested procedures and parts recommendations should have a considerable amount of merit. Obviously they do, but on the other hand, there are no doubt areas for improvement. Although we will begin our segment discussing the routine and normal maintenance of the ZR1, there are many areas where an upgrade will be suggested.


Please understand that these are personal opinions and experiences and are not intended to conflict with service procedures outlined in the appropriate service manual.

Drain, flush and refill system with new coolant as follows:
A. When engine and radiator are cool, remove pressure cap on coolant fill reservoir located at the right rear of the engine compartment by:
- slowly rotating cap counterclockwise to detent. (Do not press down while rotating)
- wait until any residual pressure (indicated by a hissing sound) is relieved.
- after all hissing ceases, press down on cap while continuing to rotate counterclockwise.
B. Open radiator draincock to drain coolant.
C. Close draincock and add sufficient water to fill system.
D. Run engine, drain and refill the system, as described in steps 1, 2 and 3, a sufficient number of times until the drained liquid is nearly colorless.
E. Allow the system to drain completely and then close radiator draincock tightly.
F. Remove and clean coolant recovery reservoir located at the right front of the engine compartment. Reinstall  reservoir.
G. Add a 50-50 mixture of water and ethylene glycol antifreeze that meets GM specification 1825-M. Fill high  fill reservoir to the base of the filler neck and add sufficient coolant to the recovery reservoir to raise level to  the full "COLD" mark on dipstick. Reinstall recovery reservoir cap.
H. Run engine, with pressure cap removed, until normal operating temperature is reached; radiator upper hose  becomes hot.
I. With engine idling add coolant until level reaches bottom of high fill reservoir filler neck.
J. Do not use pellets in LT5 cooling system.
K. Install pressure cap, making sure arrows line up with the overflow tube.
L. Check level in recovery reservoir and add coolant to full "HOT" mark on dipstick.
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