For 1990-2009 cars

# HT4100 COOLANT LOSS - NEW ADAPTER PIPE REPLACEMENT

#### VEHICLES AFFECTED: 1982-1984 Devilles, Broughams, Eldorados And Sevilles

This bulletin supersedes Product Service Bulletin 6-142, dated February 29, 1984, which should be destroyed.

A new thermostat adapter pipe kit (P/N 1628921) has been released for servicing the HT4100 engine. This kit, as illustrated in Figure 1, contains one adapter pipe, one washer, one clip, and two 'O' rings; and will: (1) provide an easier procedure for replacing a leaking adapter pipe and/or 'O' ring; and, (2) aid in the installation of the intake manifold in repairs when the water pump is not removed.

When replacing the adapter pipe to correct a coolant leak, follow steps 1 through 16 as listed below.

When installing the adapter to aid in installation of the intake manifold, follow steps 8 through 16 as listed below.

#### Theremostat Adapter Replacement Procedure

1. Drain coolant to below thermostat level.

2. Remove thermostat.

3. Remove engine water temperature sensor.

4. Remove vacuum hose from vacuum pump and move aside.

5. Remove A/C compressor front adjustment brace from the lower thermostat housing.

6. Cut adapter pipe between intake manifold and thermostat housing into two pieces.

7. Remove lower thermostat housing.

8. Clean manifold 'O' ring seat.

9. Clean thermostat housing 'O' ring seats.

10. With both 'O' rings greased, install new adapter pipe into intake manifold as far as it will go as shown in Figure 1.

11. Using a new 'O' ring at water pump, install the lower thermostat housing.

12. Install the two bolts at lower thermostat housing; do not tighten.

13. Slide adapter into thermostat housing, keeping the loose ring and 'O' ring in the manifold.

14. Install spring clip between stationary rib and loose ring.

15. Tighten the two bolts at lower thermostat housing.

16. Install A/C compressor front adjustment brace to lower thermostat housing.

17. Install vacuum hose to vacuum pump.

18. Install engine water temperature sensor.

19. Install thermostat.

20. Fill with coolant.

21. Check for leaks.

Use most applicable Labour Operation from Canadian Labour Time Guide and Claim.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.