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Additional Thermostat Replacement
 
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Pelican Technical Article:

Additional Thermostat Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$30 to $40

Talent:

**

Tools:

5mm Allen, Flathead screwdriver, floor jack, jack stands, wheel chocks, safety glasses

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

Additional thermostat

Hot Tip:

Be prepared for spilled coolant

Performance Gain:

Proper engine temperature

Complementary Modification:

Flush coolant system

The thermostat helps control the engine's temperature. If your car is running too hot and there is the proper amount of coolant in the car and it is not leaking, or your car is taking a long time to warm up, there is a very good chance your thermostat is bad and needs to be replaced.

There are two thermostats on the Porsche 951. The primary thermostat controls the flow of coolant to the radiator and opens when reaching a specific temperature (set by the thermostat) and flows coolant from the engine through the radiators. The turbo has an additional thermostat that helps regulate the temperature of the coolant that flows through the engine without being diverted to the radiator. This article will demonstrate how to replace this additional thermostat.

If you are going to be working on the thermostat, make sure the car is cool and not under pressure. Working on a hot engine or one under pressure can cause serious harm and should never be attempted. Coolant is also very toxic and needs to be collected and disposed of in accordance with your local regulations as pouring coolant down a drain or into the street is illegal. Also, be sure to wash your hands thoroughly after working around it.

If the coolant in the car is new there is no reason to replace it as long as you drain it into a clean container. Coolant is expensive and not great for the environment so if the coolant in your car is good, try and save it to reuse.

You are going to need to safely raise and support the vehicle and remove the under engine tray. Please see our article on safely raising and supporting your Porsche 944 as well as removing the under engine tray.

There are two ways to replace the additional thermostat; from above and below. While I found replacing from below easier some people do not like lying under the vehicle while working on the fluids. This article will show you both.

With the vehicle safely raised and the under engine tray removed you will need to drain the coolant from the radiator.
Figure 1

With the vehicle safely raised and the under engine tray removed you will need to drain the coolant from the radiator. You do not need to completely drain the system just enough to get the level below the thermostat. The drain plug is located on the lower left side of the radiator (red arrow). Please see our article on draining and bleeding the coolant system for additional information regarding bleeding the system when you are done.

Under Vehicle- Use a flathead screwdriver and remove the lower radiator hose (red arrow)
Figure 2

Under Vehicle- Use a flathead screwdriver and remove the lower radiator hose (red arrow), this will give you more room to work

Under Vehicle- Use a flathead screwdriver and separate the hose from the additional thermostat housing (yellow arrow).
Figure 3

Under Vehicle- Use a flathead screwdriver and separate the hose from the additional thermostat housing (yellow arrow). Next, use a 5mm Allen and make sure it is well seated and remove the two Allen screws (red arrows).

Above Vehicle- The additional thermostat is located on the right front of the motor on the coolant pump.
Figure 4

Above Vehicle- The additional thermostat is located on the right front of the motor on the coolant pump. To work on it from above you will need to remove the air box (red arrow) and turbo to intercooler pipe (yellow arrow). Please see our article on air box removal for additional assistance.

Above Vehicle- With the air box removed use a flathead screwdriver and remove the hose from the additional thermostat housing (red arrow).
Figure 5

Above Vehicle- With the air box removed use a flathead screwdriver and remove the hose from the additional thermostat housing (red arrow).

Next, use a 5mm Allen and making sure it is well seated in the bolts, remove the two bolts holding the housing in place (red arrow).
Figure 6

Next, use a 5mm Allen and making sure it is well seated in the bolts, remove the two bolts holding the housing in place (red arrow).

The bolts can get corroded over time and are very prone to stripping.
Figure 7

The bolts can get corroded over time and are very prone to stripping. If one strips you should be prepared to use an easy out to remove it (red arrow).

With the bolts off remove the housing.
Figure 8

With the bolts off remove the housing. There is a gasket between the housing and pump (red arrow). Make sure to replace this gasket every time you remove the housing.

The additional thermostat will now just slip from the coolant pump (red arrow).
Figure 9

The additional thermostat will now just slip from the coolant pump (red arrow).

The additional thermostat is just a mini version of a regular thermostat.
Figure 10

The additional thermostat is just a mini version of a regular thermostat. Installation is the reverse of removal and do not over torque the two bolts. Do not forget to fill and bleed the coolant system.

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Comments and Suggestions:
Waz951 Comments: The photos in figure 8,9 suggest the spring goes inside the water pump. However the PET and FSM show the spring going inside the plastic housing.
June 23, 2016
  Followup from the Pelican Staff: The spring / pellet faces the engine. - Nick at Pelican Parts  

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