engine and drivetrain Leaking Weber 40DFAV carb

[schuetz1619]

On my 74 2002 I have a Weber 40DFAV carburetor that I love, but when

we put it into the garage there has always been a gas smell. I have replaced the manifold-to-carb gasket, checked the float level, and installed lock washers under all screws as well as under the four carb-to-manifold

manifold retaining nuts. I still have the smell.

I then cleaned the carb and manifold so as to see where the leakage

is coming from. It appears to be from both ends of the throttle

shafts, as demonstrated the staining of gas running down onto the

base and manifold on both sides of the carb. Also, when I put my fingers under the linkage cover after stopping the engine, they came up slightly moist.

10,000 miles ago, assuming that the problem was wear of the shafts/races, I sent the carb to a carb shop. After disassembly and measurement the shop returned the carb to me untouched, saying that the shafts and races were within tolerance and that shaft replacement and rebushing would not improve on what I already have.

All of this said, the carb still leaks from the throttle shafts and

my wife won't permit it to be parked in the garage because of the

smell. Now the car, with its $5000 paint job, sits outside for the winter. Does anyone have any ideas before I spend $500 on a new 38/38?

[c.d.iesel]

replace the float needle valve with rubber tip

and ' stake ' down the brass needle seat that the needle

seals into. If the brass seat has come up abit, that will

also cause a false float level setting - possibly over flowing

float bowl, when the motor is off and 'heat soaking' .

Measure your float level after repair.

Your not using some high pressure electronix fuel pump

are you ?

Your WEBER "Needle & Seat" part number

is : 79519.______ , the 3-digits after the ._____ is your needle/float

calibrated size. It's available in 79519.125 , .150 , .175 , and .200

Look closely at your float for stamped numbers or measure it.

.

[jgerry2002]

There are also a couple of companies that make a real bearing for the throttle shaft...

[schuetz1619]

Thanks for the advice.

I have rebuilt the carb twice—most recently 5000 miles ago--both times with original Weber parts (including the needle valves with rubber tips). The seat is the machined inside top of a cylinder that screws into the carb cover. It is seated tightly, but I have no torque figure for it. Not sure how it could "come up." In any case it is tight and not going anywhere.

I am using the OE mechanical fuel pump.

I think I'll try purposely misadjusting the float in the direction of less gas and see what happens. I'm at a loss otherwise.

______________

replace the float needle valve with rubber tip

and ' stake ' down the brass needle seat that the needle

seals into. If the brass seat has come up abit, that will

also cause a false float level setting - possibly over flowing

float bowl, when the motor is off and 'heat soaking' .

Measure your float level after repair.

Your not using some high pressure electronix fuel pump

are you ?

Your WEBER "Needle & Seat" part number

is : 79519.______ , the 3-digits after the ._____ is your needle/float

calibrated size. It's available in 79519.125 , .150 , .175 , and .200

Look closely at your float for stamped numbers or measure it.

.

[schuetz1619]

There are also a couple of companies that make a real bearing for the throttle shaft...

Do you possibly know further info (company name, retailer)?

[yeewiz]

... and my wife won't permit it to be parked in the garage because of the smell. Now the car, with its $5000 paint job, sits outside for the winter. Does anyone have any ideas before I spend $500 on a new 38/38?

Doesn't the gas smell go away after the car cools down? Leave the car out until it's stone cold, then roll it in and save the $$$ paint job.

[Harv]

What kind of air filter do you have? Open K&N type? Plenty of gas smells from one of those. Also, how are the hood seals? Are toe ones on the side by the hood hold down rod in good shape? What about the one on the hood itself?

CD is probably right.

John

[jgerry2002]

usual disclaimer... no affiliation:

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,301370/highlight,weber/