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Coolant Flush and Replacement
 
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Pelican Technical Article:

Coolant Flush and Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$15 to $50

Talent:

**

Tools:

17mm, 12mm wrench, flathead screwdriver, large bucket

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

New coolant

Hot Tip:

Get a really big bucket

Performance Gain:

Fresh coolant

Complementary Modification:

New hoses

If you are changing your coolant, this is also the perfect time to give your cooling system a complete flush. While it is next to impossible to get all of the coolant and contaminants out of the system without removing the heater core lines and blowing out the heating system, this method will get the system as clean as possible and more than good enough for the next three years.

A couple of safety precautions/instructions you may want to observe before beginning:

Allow the cooling system to cool down to a coolant temperature of less than 90 degrees C. Open the cap of the cooling system slowly. Turn a conventional coolant cap as far as the first indent and turn a screwed coolant cap approx. 1/2 turn and release the pressure. Wear protective gloves, protective clothing and eye protection. NEVER pour coolant into beverage bottles, cups, etc... Someone might accidentally pick that cup up and start to drink.

Begin by safely jacking up and supporting your car. Refer to our article on jacking up your 944 turbo for more information.

The radiator drain plug is located on the lower left side of the radiator at the front of the vehicle (red arrow).
Figure 1

The radiator drain plug is located on the lower left side of the radiator at the front of the vehicle (red arrow). You will need to remove the under engine tray to access it. If you need help removing the tray please see our article on under body tray removal for additional assistance. When the coolant drains, it tends to run along the lower radiator mounting plate and drain out from it in several places. Be prepared to catch the fluid with a larger tray or a couple of buckets.

This photo illustrates the drain plug (red arrow).
Figure 2

This photo illustrates the drain plug (red arrow). It is made of plastic and will dry out over the years so be prepared for it to break off in the radiator. Use a flathead screwdriver and remove the plug.

The plug in our project car broke off half way out (red arrow).
Figure 3

The plug in our project car broke off half way out (red arrow). If this happens, use a pick or small flathead screwdriver to gently walk the plug out. Just be ready for the fluid when it finally releases.

With the drain plug removed, you can see how the coolant runs down into the radiator-mounting bracket and out along the drain holes (red arrows).
Figure 4

With the drain plug removed, you can see how the coolant runs down into the radiator-mounting bracket and out along the drain holes (red arrows).

While the coolant from the radiator and most hoses will drain from the radiator drain plug, there is still coolant in the block.
Figure 5

While the coolant from the radiator and most hoses will drain from the radiator drain plug, there is still coolant in the block. The drain plug for the block is located on the rear right side (red arrow). You can get access to it by reaching up between the exhaust and block. If you remove the plug, make sure to install a new washer when re-installing it.

Move to the top of the engine and open the cap on the coolant reservoir to help break the vacuum seal and drain the fluid (yellow arrow).
Figure 6

Move to the top of the engine and open the cap on the coolant reservoir to help break the vacuum seal and drain the fluid (yellow arrow). You are going to need access to the vent plug (red arrow) on the top of the motor to vent the system while refilling it. You can vent the system without removing the turbo pipe, but it is going to get messy. I prefer removing the pipe.

Optional- Disconnect the line running to the turbo pipe with a 17mm wrench.
Figure 7

Optional- Disconnect the line running to the turbo pipe with a 17mm wrench. Note that there are two washers (red arrows) that need to be replaced if you remove the line.

Optional- Disconnect the clamp over the pipe by reaching down and unclipping it.
Figure 8

Optional- Disconnect the clamp over the pipe by reaching down and unclipping it. Then remove the lid. Next, use a flathead screwdriver and loosen the hose clamps on both ends of the pipe (red arrows).

Optional- Remove the pipe from the engine (red arrow).
Figure 9

Optional- Remove the pipe from the engine (red arrow).

You now have lots of room to access the 12mm vent bolt as well as place rags to catch all the venting fluid.
Figure 10

You now have lots of room to access the 12mm vent bolt as well as place rags to catch all the venting fluid. To flush the system: close all the openings and fill the reservoir with distilled water, run the motor with the heater on full for a few minutes then drain and repeat until the water runs out clear. To fill and vent the system: the best way is to rent or borrow a coolant system pressure tester; this will allow you to fill, pressurize and vent the system all at one time. If you do not have a pressure tester, you can still fill and vent the system, but it is important to get all of the air out of the system or the engine will run hot. Raise the front of the vehicle up, this will get the vent port to the highest point in the system. Note: If you have completely drained the cooling system (using the drain plug on the side of the block) you may want to disconnect the upper radiator hose (at the radiator). Hold it up in the air, and fill the block by pouring coolant into the hose. It's best if you open the vent at the outlet of the cylinder head so you can tell when the block is full. Do not fill the coolant hose completely, as it will make a mess when you reconnect it back to the radiator. Next open the 12mm vent bolt and slowly pour coolant into the reservoir until coolant starts to come out from the vent hole. Close the vent hole and reservoir and run the motor for a few minutes, open the bleed screw (use caution as steam and very hot coolant will escape). Perform this procedure a few times until no steam exits. Check the reservoir and add coolant as needed.

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