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The thermostat on the 1988 Buick LeSabre is located partially inside the intake manifold and the thermostat housing. Because the thermostat sits higher than the fluid level in the radiator, replacing the thermostat in the LeSabre is an uncomplicated task. Fortunately, the thermostat housing is not hidden among engine accessories. This makes it easier to reach, remove and replace a broken thermostat.

Instructions

1

Follow the upper radiator hose to the point where the hose connects to the LeSabres engine. The metal connector to which the hose connects is the thermostat housing.

2

Disconnect the radiator hose from the housing by squeezing the pressure tabs on the radiator hose clamp together with a pair of pliers. With the pressure released, pull the hose off the housing. A small amount of fluid may run onto the engine block. To minimize this, hold the hose vertical for a few seconds to drain the fluid back into the radiator.

3

Remove the two bolts that secure the thermostat housing to the Buicks intake manifold with a 7/16-inch socket and ratchet. With the bolts removed, apply pressure on the side of the housing with the ball of your hand to break the seal between the housing and the intake.

4

Pull the old thermostat out of the intake manifold and plug the hole with a shop towel to prevent anything from getting into the coolant system of your Buick.

5

Scrape all the old gasket material off the bottom of the thermostat housing and the mating surface of the intake manifold. Brush off any debris with a shop towel.

6

Remove the shop towel from the intake manifold and place the new thermostat into the hole. The end with the large spring submerges into the intake manifold and the end with the pin sits inside the thermostat housing.

7

Place a thin bead of RTV gasket maker on the bottom edge of the thermostat gasket. Allow the RTV gasket maker to firm up for approximately 20 minutes. This creates a small layer of "skin" on the RTV.

8

Place the thermostat housing onto the intake manifold and bolt it into place. Do not wipe off any excess RTV. It serves as additional sealant.

9

Squeeze the pressure tabs on the radiator hose clamp. With pressure released, slide the hose onto the thermostat housing and then let go of the tabs.

The 6.0-liter Powerstroke was a turbo-diesel engine used in a wide variety of Ford trucks and vans. Until 2007, all Powerstroke engines were made by a subcontractor, Navistar. Unfortunately, Navistar had poor quality controls and all the engines produced by Navistar had numerous problems. The 6.0-liter Powerstroke cost Ford millions in warranty repairs, in addition to the extra cost of redesigning the engines.

Unreliable Variable Vane Turbocharger Solenoid

All turbo-diesels rely on a turbocharger to properly burn the fuel/air mixture. On the Powerstroke, a variable vane is used to adjust the air intake coming from the turbocharger into the engine. A solenoid controls the degree of rotation of the vane. On Navistar Powerstrokes the solenoid detaches easily, in addition to corroding early. Damage to the solenoid prevents the variable vane from changing position. A Powerstroke with a damaged solenoid will suffer power loss throughout the power band.

Carbon Deposits

All Navistar engines, not just the Powerstrokes, suffer from excessive carbon deposits. Carbon deposits are a byproduct of the combustion of carbon-based fuels like diesel. In a well-designed engine the carbon is pushed out during the exhaust cycle of the combustion chamber. Unfortunately Navistar did not get the fuel injection timing right, and carbon builds up with each combustion cycle. A Powerstroke with carbon buildup shows excessive black exhaust smoke as well as power loss at higher engine speeds.

Defective Exhaust Back Pressure (EBP) Sensor

The exhaust back pressure sensor tells the engine how much resistance is in the exhaust system. Excessive back pressure can choke the engine and the turbocharger. In the 6.0-liter Powerstroke, the sensor detaches easily from the exhaust system, depriving the ECU of any data. A detached sensor will lead to exhaust gases flowing back into the combustion chambers, stalling the engine. Additionally, the exhaust gases will flow back into the turbocharger and stop it from spinning.

Fuel Injector Harness Chafing

The most dangerous defect in the 6.0-liter Powerstroke is the easily damaged fuel injector harness. The lines are laid across the engine support struts, which shift as the engine torques. This shifting chafes the fuel lines to the point of leaking. Even though diesel fuel is less flammable than regular gas, it is still a fire hazard. Do not operate any vehicle that is leaking fuel. If there are fuel puddles under the engine, then the fuel lines have been damaged. Contact a Ford dealership for repairs. Ford has bought back some trucks with this issue rather than pay for the repairs.