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OT: Auto Vacuum question

Since this is a pretty good source of brain power and and general overall knowledge I'll try here since I do not seem to get much from any of the automotive groups. I need to replace a vacuum check valve on a 1990 Dodge Dakota and unfortunately Dodge doesn't carry the part any more (Thank you Daimler(sp?) seems after they bought Dodge the S**t Canned anything 10 years and older I can't even buy a service manual) and the only thing I have found to replace it is one from the 'Help' parts section in the local auto parts place. My big concern is that the unit that was in the truck originally has a large diameter hole/nipple on both sides of the main disk body where as the 'replacement' one has one close to the same size and the other is much smaller. I can make up an adapter to fit it but I'm not up much on vacuum theory and wonder how much the smaller diameter pipe will affect the vacuum circuit. Anyone care to give a short disertation on vacuum circuit opperations???

Bill

Reply to
Bill
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You didn't state the function of that vacuum check valve, so...

Whether or not the reduced diameter will give you problems is a function of how large a flow rate through it is needed to permit proper operation of whatever reservoir is being evacuated out or "vacuum motor" device is being activated.

But, since engine intake manifold vacuum can drop to near zero under hard acceleration, most likely that check valve is there to hold the vacuum inside a storage reservoir during acceleration, and the "reemptying rate" of that container must have been designed to accept the that it'd have to put up with a low source vacuum at certain times.

Since "One test is worth a thousand expert opinions", I'd do the adaption, and as the Brits say, "Suck it and see." (Just make sure you "polarize" that check valve the right way around. (Ducking....)

Jeff (Who's waited about thirty years for the perfect occasion to use that Brit expression...)

-- Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone to place the blame on."

Reply to
Jeff Wisnia

On Mon, 20 Oct 2003 16:31:27 -0400, Jeff Wisnia pixelated:

That's a biggie.

Chances are good that it's a dash-ducting-door-motor and the valve will be OK. If anything, it might take an extra 1 or 2 seconds to close a vent, etc.

As a wrench (in another life), I'd have to give you an A+ for that entire post. Got it in one.

ROTFLSHIAPMP! 2 points, Jeff.

----

- Nice perfume. Must you marinate in it? -

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Reply to
Larry Jaques

I've also used those "Help" generic replacement parts. I think you're referring to the check valve for the power brake booster, just as a guess.

It'll probably be fine, since the hose ID for boosters is relatively large compared to various other vacuum components. If you experience any different braking during your cautious but extensive road test, ask the parts store to show you the entire parts catalog listing for the "Help" product line. A different parts store/supplier might have a valve with the same OEM ports, look for a Dorman parts supplier, for example.

WB ................

Reply to
Wild Bill

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Reply to
John Kunkel

Just get an inline brake booster check valve - many vehicles used them

- old Toyotas are a good source.

Reply to
clare

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