Heater Hose Replacement, '78 - '84
This task isn't too difficult, just time consuming.
Note: for '78 to '84 and earlier models (maybe later Euros too up to 32 valve engine) I discovered that Porsche has discontinued the custom molded heater valve to engine hose P/N 928.574.567.02 (only about 2 inch/5.1 cm long). The heater valve hose connector size is a larger diameter than the engine hose fitting. Per Dave Roberts of 928 Specialists, the Porsche rep says just use P/N 928.574.567.03 and "tighten the hose a bit more" so it doesn't leak. This didn't work for me, I ended up with a green swamp in
the engine "V".
If you must use the "new" one size hose, I would suggest using 2 or 3 clamps over the engine side fitting to ensure these new "oversize" hoses don't leak. At a price of over $8.00 for the Porsche P/N short length, I'd suggest just buying standard hose for a few cents.
Now, to the how-to part: [Performance Products has a nice diagram on page 104 of their latest catalog, part numbers below are for '83]
1. Remove the metal under-engine wind plate, drain the radiator water.
Note: I removed the plastic radiator plug (front right). [use care, it
broke when I replaced it. A new one costs over $5.00 from the dealer]. In
the future, I will just remove the lower radiator hose.
2. Hoses to heater core: [P/N 928.574.587.03, 928.574.589.04]
- Remove the Air filter
- Loosen the two bolts inside airbox (the bolts do not come out of the airbox). [there is no need to remove the mass/air "flapper" sensor from the airbox].
- Gently pull the airbox out of the way, being careful not to twist the flapper box wires.
- Remove the plastic cover behind the hood/over the windshield wiper mechanism. Just pull up at the rubber sealing strip. You'll see the hoses connecting to the heater core next to the wiper motor.
- Loosen the windshield washer motor to gain access to the hoses
- remove the nut holding the wiper rod to the motor
- spray some WD-40 or penetrating oil on the rod connection
- pry the wiper rod from the motor
- remove the 3 nuts that fasten the motor to the bracket
- pull the motor out of the way (no need to disconnect the wires)
- Loosen the heater hose clamps to heater core. . If the hoses are baked on the fittings, you may need to slice them to get them loose.
- Pull the hoses through the firewall (for installation, smear a little dish wash soap over the hose to ease threading the hose through the firewall).
2(a). Hose to metal Y
The metal Y is near the reservoir. Loosen the clamp, remove the hose. Note for replacement, there is a clamp that holds the hose up to the firewall and a rubber fitting to hold the hose in place.
2(b). Hose to heater valve
Loosen the clamp at the heater valve, remove the hose.
3. Engine to heater valve [P/N 928.574.567.03, see warning, not worth the price, use std. cut of hose]
I'd suggest replacing the heater valve 928.574.573.03 when doing the hose change. It is pretty inexpensive (Porsche-wise). Simple screw/unscrew.
After hoses to heater core are replaced, the airbox need to be put back into place. Please carefully guide the mass air flapper valve back into place. Then tighten the airbox bolts.
4. Hose: pipe to regulator housing [center front of engine] P/N 928.106.321.03
This is easy, just remove the clamps and remove the hose.
5. Hose: connector to water reservoir [P/N 999.181.709.50]
This is a straight shot hose, maybe std. hose could be used.
6. Hose: radiator to fitting [P/N 928.106.277.01]
This is a long hose, you'll need the Porsche hose, simple unscrew clamps and "unthread" across radiator and into engine compartment.
7. Hose: pipe to reservoir [928.106.323.01]
At this point, I didn't see an easy way to move/remove the reservoir (was a little too tired). Dave Roberts suggested that the reservoir might not have to be removed. This is for next time.
Replace the hoses and tighten the clamps. For installation onto tight fittings, try using a little dish wash soap.
8. Replace the radiator plug (if removed). Be sure to inspect it for the little "o" ring. My 83 original plug broke upon installation. A used one from my local shop had a brittle "o" ring and leaked. A new one fixed it (a few days and miles later). This is why Id recommend not removing this plug.
9. Refill the reservoir. Start first with a gallon of antifreeze, then refill the antifreeze jug with water and use for refill. This ensures at least a 50% mix.
10. Crank up the shark and let it warm up. Check for leaks above and below. Install the under chin pan.
11. Drop from jack stands. Let cool, and check the water level, reservoir water level. It should be a little more that half full when cold.
928 Specialists has pretty competitive hose prices. Shop around if you have the time.
I hope this helps someone in the future.
'83 S (now with new hoses)
Charter Member of 928 Owners Club
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