944 Bleed the cooling system without a mess!

[Leo944]

One of the timing belt sprockets on my ’86 944 failed last summer taking the valves with it. Many hours of hard work and dollars later; I find that the car keeps running on the hot side and very hot when idling, even with the fans running. I also have intermittent heat out of the heater. All signs of air in the cooling system.

I have bled the system a couple of times following the procedure outlined in Porsche’s manual without much success. See the manual’s steps below. I did a lot of research to learn how others have tackled –and solved—the infamous coolant bleeding problem.

Clark’s –Garage recommends the use of a cooling system pump as the preferred method and the Porsche manual method as the second best.

I came across this video on YouTube which avoids the inevitable coolant spill and it piqued my interest: https://www.youtube.com/watch?v=Z6n4ubS6C5M

I then found this great post on the subject: 944 Forum - Bleeding ALL the air out - WORKS!

Using the pump seems the best and easiest way to bleed the system but one still has to deal with the messy coolant overflow. I decided to make the grease fitting and vinyl tubing contraption as a first step and skip the pump step for now. I could always rent the pump at a later time should the problem persist and use the fitting-tubing doohickey to divert the coolant overflow to a container avoiding the coolant spill.

Parts:
1. My local Advance/Autozone/NAPA stores didn’t have the 8mmx1 grease fitting in stock, so I ordered it online from HomeDepot.com and had it shipped (free) to my local store for pick-up. SKU #700632, cost $0.94
2. About 5ft of ¼-inch ID vinyl tubing. Home Depot – 10ft for $3.25
3. A small clamp to secure the tubing. I used a cable tie.

Assembly:
1. Place the grease fitting in a vise as drill out the sealing ball and spring. I thought this would be a breeze but the metal alloy of this part is extremely strong and it took some doing to finally drill thru. I first tried drilling at the top of the fitting but ended up drilling out the bottom first. This step requires patience and sharp drill bits.
2. Flush the inside of the fitting with brake cleaner or similar solvent to remove all lubricant/metal residues
3. Insert fitting into tubing. The fitting OD is .26-in and the tube is .25 --not a very tight fit so secure with clamp/tie

How-to Steps:
1. Raise the front end of the car. I placed mine on ramps
2. Turn the heater’s temperature control to the max
3. With a cold/cool engine, remove the bleeder plug and reservoir tank cap
4. Fill reservoir tank to the max level. Some coolant should seep out of the bleeder. Leave the cap off
5. Screw the fitting into the bleeder hole and place the other end of tube in the reservoir tank or a container. I simply elevated it.
6. Start the engine and run to operating temperature (fans turn on)
7. Keep an eye on the temperature gauge. Don’t let the engine overheat
8. Add additional coolant as needed
9. Continue until a solid coolant flow is achieved out of the bleeder, i.e. no air bubbles or foaming
10. Place/keep the tube upright so there is a small amount of coolant blocking air from re-entering the system.
11. Replace& tighten the reservoir cap
12. Turn engine off
13. Let engine cool to avoid contact with very hot coolant
14. Wrap a shop towel around the fitting to catch spilled coolant. Remove the fitting and screw on plug. Add coolant if necessary
15. Road test. Good luck!

[Roger at Pelican Parts]

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[Leo944]

Thanks for your kind words, Roger.

I'll keep your suggestion in mind.

Best,

Leo

[Waz951]

Good simple and cost effective solution.

Another option is to use a M8x1 to 1/8" Pipe Fitting adapter. That will allow you to use 1/8" NPT to hose barb on the end. Or if the first adapter is male to male, can probably just clamp the hose on the threaded end. Adapter is about $10 so a little more costly but you don't have to drill out the grease fitting.

[GTR34]

Fantastic write-up! I've done this before with a grease fitting and it is great.