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Coolant Flush

Thanks to Paul Nimz, updated 8/25/04

How to flush the cooling system on a V8 SHO. The cooling system on the 3.4L V8 holds 10.8 quarts or nearly three gallons. So you should have 2 gallons of antifreeze and 2 gallons of distilled water to make your mix. Mix one gallon of antifreeze to a 70/30 strength and the other at 50/50. The use of distilled water, although not necessary will go a long way towards keeping the system cleaner.

First you need drain the system and refill with tap water and the flush product. Then drain again, flush with water, and refill with antifreeze.


Items needed:

pliers, screwdriver, various metric wrenches/sockets, jack etc..... small funnel which will fit into a 5/16 hose

5 gallon bucket (if interested in recovering the waste products)

3 new hose clamps 2- #6 and 1- #8

2 gallons distilled water and 2 gallons of antifreeze used to make 1 gallon of a 70/30 mix and 1 gallon of a 50/50 mix.

1-1 gallon clean container (to mix the 70/30 in)

1000 mL measuring cup (too measure the H2O/antifreeze)

1 can of radiator flush

5/16 hose barb with garden hose shut off (optional)

At least a quart of cold Old Milwaukee (used to sooth any possible hot coolant/engine burns)



1) With a cold engine, raise and support the front end. On the passenger side under the degasser tank is a 1" hose, which is connected to a tee on the lower radiator hose. There is a union on this hose and taking the hose apart here is the easiest place while also being the lowest part in the system. You can alternatively remove the apron/spoiler as one piece by taking out the 3-8mm bolts in the rear and the 11 screws in front of the spoiler to gain access to the radiator petcock.

2) Allow all the old antifreeze to drain from the degasser and radiator.

3) Remove the 5/16 ID inside hose from the degasser, discard clamp. Disconnect one of the small water pump hoses at the water pump. It doesn't matter which one.

4) Attach garden hose the 5/16 ID hose, lower vehicle with the petcock still open.

5) Slowly turn on water and run until clear water comes out of the water pump and the overflow tank.

8) When the water is clear, reattach water pump hose temporarily (no clamp is needed). Then while holding your finger over the open degasser hose barb, blow low-pressure air into the unattached 5/15 ID degasser hose. Continue until as much water as possible has been removed. This removes water from the block and heads.


Refill with water and flush chemicals

1) Raise vehicle and reconnect hose or close the radiator petcock.

2) Remove outside 3/8 ID degasser hose, discard clamp.

3) Attach small funnel to the 5/16 ID degasser hose.

4) Reattach all hoses using new clamps

5) Add the flush chemicals and fill with water topping off the degasser tank.

6) Drive for 30 miles of 30 minutes.

7) Repeat all seven steps of the "Drain" procedure listed above.


Refill with Antifreeze

1) Repeat steps 1 and 3 (not 2) of the "Refill with water and flush chemicals" procedure listed above.

2) Slowly pour the 70/30 mixture into the engine first while watching the water pump outlet. When the water is driven out and the antifreeze is the coming out color you want from the water pump reconnect the water pump hose using new # 8 clamp.

3) Slowly pour in the remaining 70/30 mixture and continue with the 50/50 mixture until the degasser tank is 2/3 full.

4) Attach all hoses and tighten pressure cap then bring engine to normal operating temperature then allow to cool.

5) Watch the degasser tank and top off as necessary over the next couple of days.

Pretty easy to do really.

Paul Nimz
'97 Tr
'93 EG mtx

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