MFI Pre-heater hose

[tobluforu]

I just received both hoses from pelican because the old ones on my car had had it. Pelican sells an inner and an outer hose, but the outer hoses I had was plastic on the outside, and pelicans is not. Also, the inner hose which connects to the pump, and the fitting on the engine tin is to damn big. Sure I can crimp it on which I will, but what's up with that? So my next question is if anyone has used any other type of hose to do the same job, like SS braided heater hose, etc?
Thanks

[Grady Clay]

tobluforu,

This is going to stretch my lame memory but I’ll try.
The outer hose:
The original hose, ’69-’72 was paper/alu foil.
In ’73 the hose changed to plastic as well as all the replacements.
It is good that the paper/foil is available for original appearance but it is less durable when washing the engine.

The inner hose has always been a bit loose (the hose clamps crush it a bit) on the thermostat.
It may be that the currently available hose is a bit larger still.

Remember, these hoses were German ‘standard’ for VW and the like – they were not produced ‘custom’ for our Porsche application.
Porsche (and Bosch) had to ‘make do’ in some applications.

Replacing these hoses with new was a ‘replace every maintenance’ item when these MFI 911s were in daily service.

Please correct or add to my memory.

Best,
Grady

[tharbert]

I found a replacement paper/foil large mfi pre heat tube at my FLAPS. The box was marked in mm and inches. I took a piece of the old hose (because that's all I had) over there on the off chance they would have something close. It matched up perfectly.

[cmcfaul]

Anyone know why two hoses? I replaced mine recently and noticed the difference between the plastic coated and paper coated. Would not one, more modern, hose be better?

Chris

73 911 E

[tobluforu]

Grady,
I have probably had that plastic outer piece on my 72 for 15 plus years, but it has seen its last day. The inner piece I have replaced a few times since it's constantly being taken off and put back on and the ends go to hell. And I guess they no longer make the outer plastic piece, or at least pelican doesn’t have it from what I can tell? You are right that they have always fit a little loosely, and It's been so long since I bought this hose that for some reason I thought they would fit properly now . Makes sense that this hose is not a custom piece as well. I think the OD of the pump port is 1 inch, give or take and I'm all about sprucing the looks of my engine compartment up, so has anyone used anything else?
Thanks

[Grady Clay]

Chris,

The ‘two-hose’ configuration is for heat insulating purposes.

The hot air flow to the thermostat must be matched to the warm-up characteristics of the engine
Critical are the condition of the left heat exchanger and the type and condition of the path of the hot air to the thermostat.
In very cold weather it is necessary to wrap the double hose and thermostat in more insulation, otherwise the thermostat won’t ‘turn off’ (or soon enough) and oil dilution with gasoline results.



tobluforu. To my eye, the most common visual deficiency are the two heater tubes and the large clamps.
These need to be original paper/alu foil and the proper N-S clamps.
We need to research the original orientation of the clamps.
While they look appropriate, you must be careful to not wash or blow them with high pressure water or air.
Properly maintained, they last several years.

Post some images of your engine and I’ll tell 2¢ what I see.

Best,
Grady

[tobluforu]

Grady,
Thanks for the info. but the engine is in somewhat disarray, but will post a pic when I have all the linkage, air cleaner etc installed-right now it looks like hell. Just trying to button it up before she see's daylight again; darn car has had its tail in the air for 6 months now due to a clutch job gone to hell and having a non-heated garage in Chicago. Plus I'm getting old and for some reason I forget where some parts have disappeared to.
But, I have one year old SSi’s with a new steam hose, but when I dropped the motor this last time I ripped the pre-heater hose.
Thanks for the help.

[bavaria911]

Could someone post pictures of the two types of hoses.
Thanks,