Re: [DML] vacuum leaks

["content22207" <brobertson@xxxxxxxxxxxx>]

Not just K-Jetronic -- all fuel metering devices (including
carburetors) are unable to deliver a proper fuel/air mixture when
unmetered air is sucked into the engine through a vacuum leak.

If the leak is big enough (what I call "catastrophic" -- usually
anything more than 1/4"), the engine may not even run.

K Jetronic does suffer from a plethora of potential leakage points,
which you address with that comprehensive O ring kit. Note also that K
Jetronic PCV is constant (calibrated nipple vs traditional valve),
which I guess is the source of unconventional leaks through the
dipstick tube etc (Workshop Manual Page D:06:03). And as Warren and I
both attest, those big plastic lines to the front of the car can crack
and leak.

Old vacuum operated diaphragms are another common source of leaks. Our
cars have 3 in the HVAC ductwork under the dash, 1 each on the
charcoal canister, heater core shutoff valve, and ignition advance,
and a big one on the power brake booster. HVAC mode switch itself can
leak as well. Even though the vacuum canister is well protected, it
could be yet another source of leakage.

I've also seen several cars on which the plastic line to the heater
core shutoff valve is cracked, though that should only present a
problem at Max A/C (and a very small one at that).

A person would have to be masochistic not to replace every vacuum line
and seal whenever they are exposed for other maintenance (especially
if they are original from the factory!).

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "John Hervey" <john@xxxx> wrote:
> 
> As Warren say's that the vacuum is very important to the proper
tuning and
> running of the car. The CIS Fuel system depends on the vacuum to be
correct
> to help in the efficient running and fuel mixture. If you draw
vacuum from
> some other place in the system and the air flow meter doesn't
deflect down
> to the proper position then the mixture will be wrong.
> I discovered this a long time ago and developed the Silicone replacement
> hose kit for the complete engine compartment. It will last longer than
> rubber lines and handles the temperature a lot better. Silicone
vacuum hose
> lines are rated at 250 degrees F.
> I have the complete system for $49.95.
> John Hervey
>
http://www.specialtauto.com/delorean-parts/images/Vacuum-silicone-kit-black.
> jpg
> 
> 
> -----Original Message-----
> From: Warren Wallingford [mailto:warren@xxxx]
> Sent: Thursday, April 07, 2005 11:39 AM
> To: dmcnews@xxxxxxxxxxxxxxx
> Subject: [DML] vacuum leaks
> 
> 
> 
> 
> I've noticed a couple of postings concerning bad idle and
performance due to
> suspected vacuum leaks.  This is a constant topic of conversation with
> owners and mechanics that call DMCH for tech help.  The intake of the
> Delorean's PRV can be tough to seal.  There are a lot of places for
it to
> leak, some of them obscure.  I talked recently with a shop that had done
> what I considered to be an extraordinary job of finding a hole in the
> system.  By clamping of hoses, they had traced their rough idle to a
crack
> in the rigid vacuum line running forward from the right side of the
engine
> to the front of the car to feed the brake booster.
> 
> The lesson is that as the car gets older, there will be different
and new
> places for it to malfunction.  Let's not forget that engine vacuum
puts the
> power into the power brakes and pulls the flaps that direct hot and
cold air
> from the dash.  The hot water valve is modulated by vacuum.  All of
these
> places are potential trouble spots whose only noticeable effect is
on engine
> performance.
> 
> By the way, we have those vacuum lines in stock. Part number 100416,
$15.49.
> Click the link-see the picture.
> http://www.usadmc.com/dmcstore/ViewPart.asp?PID=108&Qty=1&ShowCart=true
> 
> Warren Wallingford
> DeLorean Motor Company (Texas)
> 15023 Eddie Drive
> Humble, Texas 77396 USA
> 
> http://www.delorean.com
> 800/USA-DMC1
> 281/441-2537
> 281/441-2813 Fax
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> 
> 
> 
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