Installing Spring-Loaded T-Bolt Clamps (TBLS)

Spring Loaded T-Bolt clamps are often used on heavy truck coolant and charge-air systems. The intent of the coil spring is to accommodate both expansion and contraction of the hose connection.

When installing these clamps, one must take care that the coil spring is not fully bottomed out. For in the fully bottomed out condition that expensive spring has been converted to nothing more than a solid spacer. While this condition may allow for some contraction of an assembly, there is no way that hot expansion can be accommodated.

When the spring is fully bottomed out and the system does heat up, the hose will be seeing excessive clamping pressure, which could lead to a shorter service life, damaged fittings or both.

Accepted installation practice is to turn the nut back two full turns from the coil-solid position. If unsure, use a feeler gauge or similar and check for positive clearance between the middle coils. With the usual 1/4-28 thread and 3 full coil gaps there should be about .022 inch clearance between the middle spring coils. This equates to two (2) turns of the nut.