Finding radiator thermostat on 1986 gmc jimmy 5.7l

wrong thermostat,or wrong radiator cap,clogged radiator,check the easy stuff first.radiator caps are made for different pressures also...

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the upper radiator hose always ENDS at the thermostat.

hi, if you are speaking of a 1999 gmc jimmy, yes, the engines in both vehicles use the same thermostat. the thermostat is located inside the thermostat housing which is connected to the upper radiator hose, and mounted on the top of the engine to the intake manifold. it maybe a plastic housing, or aluminum, it will have two bolts. follow the upper radiator hose away from the radiator and where it ends, is where the housing is.

follow the upper radiator hose (large hose at top of radiator) from radiator to engine the housing it goes to is the thermosat housing the thermostat is under that housing

For this models:
1986 GMC S15/T15 4WD P/U 2.8 liter V-6 VIN "R"
1986 GMC S15/T15 4WD Jimmy 2.8 liter V-6 VIN "R"
1986 GMC S15/T15 2WD P/U 2.8 liter V-6 VIN "R"
1986 GMC S15/T15 2WD Jimmy 2.8 liter V-6 VIN "R"



Hope helped woth this. Remember rated this help. Good luck.

Follow the upper radiator hose to the outlet elbow (the waterneck!) and it is located under it:

Removal & Installation

1. Drain the radiator until the coolant level is below the thermostat level (below the level of the intake manifold).
   

CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

1. Remove the water outlet elbow assembly from the engine. Remove the thermostat from inside the elbow.
   
2. Install new thermostat in the reverse order of removal, making sure the spring side is inserted into the elbow. Clean the gasket surfaces on the water outlet elbow and the intake manifold. Use a new gasket when installing the elbow to the manifold. On later models the thermostat housing may have been sealed with RTV sealant. If so, place a 1/8 inch bead of RTV sealer all around the thermostat housing sealing surface on the intake manifold and install the housing while it is still wet. Refill the radiator to approximately 21/2 inch below the filler neck.
   

If the thermostat is equipped with a pin hole, be sure to install pin side facing upwards.

Hello? Get some helpful tips here. Manuals Schematics Comphotechtronics

Follow top radiator hose to engine. Thermostst is under cover hose is connected to. If this is helpful, please post as such. If it is spotted, please post as fixya!! TY

if you follow the radiator hose on the drivers side of the radiator up to the motor. you will find the spot it is connected to with a hose clamp. under that housing is the thermostat.

hope this helps ans let me know if I can further help you

Tom