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.

By far, the most common complaint made by the Corvette owner is "overheating." There are several concerns here.
First, the Corvette ZR1 has no front grill therefore, it relies heavily on the air deflectors underneath the front bumper to direct airflow through the radiator to dissipate heat. Damaged or missing deflectors will cause overheating. The "bottom feeder" design also works wonderfully as a vacuum cleaner for our roadways, however, the downside of this is that the Corvette's radiator becomes highly susceptible to accumulating debris which will reduce airflow and therefore increase operating temperatures.  Depending on your climate, the ZR1's cooling system requires regular maintenance.
Once a year the system should be drained (best done by loosening the lower radiator hose) and refilled with an approved coolant. We also highly suggest using distilled water because the aluminum alloys present in the LT5 and radiator actively promote the formation of scale within the system.  There is much discussion of thermostats for the LT5.
A word of caution. The LT5's thermostat has several functions. In addition to performing the duties of a thermostat, it also provides a by-pass function for the radiator in the event the amount of coolant exceeds the capabilities of the radiator. Use of the incorrect thermostat can result in blown hoses and even blown apart radiators.
The LT5 is equipped with a 195 degree thermostat but we have also had great results using the Stant 180 degree stat (part #14068). As previously mentioned, the radiator is highly susceptible to restrictions and blockage. This is the main cause of any rise in operating temperatures and should be addressed first. This airflow restriction occurs when particles are collected in the small space between the AC condenser and the radiator and is not visible until the top radiator shroud is removed and the radiator fully viewed from the top. Radiator removal is not as involved as it may first appear and we find that periodic removal and cleaning is very effective.
Also be sure to inspect the AC condenser due to the fact that it is installed in front of the radiator. It too must not be obstructed or possibly damaged by road debris.
As we have said, keeping your LT5 cool and the cooling system serviced are crucial to the LT5's durability. Although there are some larger aluminum radiators available, the stock system should provide adequate cooling under most street operations if kept clean and unobstructed. The LT5 is susceptible to head gasket problems if allowed to over heat because of the close proximity of the lower part of the cylinder to the coolant passage. If your LT5 uses coolant and you see no external leakage, you may have a seeping head gasket and should have it check immediately.
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