Vacuum leak tested question

[delorean928]

Hi, I just did a vacuum leak test with a smoke machine and I have a leak on the throttle body at the mixing screw hole. Is there suppose to be a plug there?
I also had a small leak at the yellow spot (see photo) it looks like sealant but pierced. Should it be pluged too?
Any help appreciated :)

[krs09]

The mixing screw hole should be plugged. You may be able to get a screw in there or I even heard people using golf tees. The yellow spot is weird, mine is completely sealed over so I would cover that for sure maybe just a little RTV can help. With vac leaks your gonna have all types of goofy problems

[David T]

The mixing screw hole should be plugged. You may be able to get a screw in there or I even heard people using golf tees. The yellow spot is weird, mine is completely sealed over so I would cover that for sure maybe just a little RTV can help. With vac leaks your gonna have all types of goofy problems

I am guessing you did not mean the throttle body, you are talking about the mixture unit, the one with all of the hoses on top. It has a hole which you insert an allen wrench to adjust the mixture. It MUST be plugged or you have a huge vacuum leak. Temporarily you can use a small piece of electrical tape. If the motor is running with that open hole you probably will have to adjust the mixture screw since it is set WAY too rich to compensate for that leak. As for the leak on top of the idle motor (that yellow spot) it is probably minimal but a little RTV should seal it up. Make sure the "O" ring under the mixture unit for the air tube to the idle motor is not leaking and all 6 injector seals.

[delorean928]

Thank's for the fast answers!
In fact I ordered 6 injector seals cause I got a huge vac leak on one. May be that will solve a part of the idle hunt problem :shyshy:

[mluder]

Hi, I just did a vacuum leak test with a smoke machine and I have a leak on the throttle body at the mixing screw hole. Is there suppose to be a plug there?
I also had a small leak at the yellow spot (see photo) it looks like sealant but pierced. Should it be pluged too?
Any help appreciated :)

Just out of curiosity, what was the source you used for smoke and where did you introduce it to the system?

Cheers
Steven

[delorean928]

Here is a photo of the machine I used. I connected it on the main vacuum line just between the engine and firewall. I disconnected the T and made the test for the side of the line that goes to the AC control and brake master cylinder then the test for the engine side. I'll take a photo of where I connected tonight and post it.

[delorean928]

Here circled in red is the vac line where I connected the smoke machine I borrowed for the test.

[mluder]

Here is a photo of the machine I used. I connected it on the main vacuum line just between the engine and firewall. I disconnected the T and made the test for the side of the line that goes to the AC control and brake master cylinder then the test for the engine side. I'll take a photo of where I connected tonight and post it.

Thanks!... I assume you rented the machine from an auto parts store?
EDIT: OH... I see you borrowed it - same question though... from a friend or shop?

Cheers
Steven

[delorean928]

I borrowed it from one of the schools where I work. They have a car mechanic dept. :)

[David T]

I borrowed it from one of the schools where I work. They have a car mechanic dept. :)

When I connect a smoke machine I try to disturb as little as possible so I get an accurate test. I take off the air cleaner box, cover the air inlet for the mixture unit and pump into the crankcase vent hose. With the air filter box off I can get a better look at the top of the motor.

[delorean928]

When I connect a smoke machine I try to disturb as little as possible so I get an accurate test. I take off the air cleaner box, cover the air inlet for the mixture unit and pump into the crankcase vent hose. With the air filter box off I can get a better look at the top of the motor.

That's what I did too. I found a leak at the mixture adjust screw cause I had no plug. I found another leak at the oïl filler cap assy and I changed the big O-ring around it. I also found a leak at an an injector seal. I planned and ordered 6 to change them all. I'll also change the O-ring around the air inlet so the engine will tale air only from the right place thru the air filter.
Beside that everything is fine.

[Trstno1]

Does someone have a video showing how to test for vaccum leaks on our cars? Maybe something showing where to introduce the smoke into the system?

[David T]

Does someone have a video showing how to test for vaccum leaks on our cars? Maybe something showing where to introduce the smoke into the system?

There are many ways to do the same thing. I remove the air cleaner, seal the air intake and push the smoke in through the oil vent hose.

[Trstno1]

There are many ways to do the same thing. I remove the air cleaner, seal the air intake and push the smoke in through the oil vent hose.

You do that without the engine running right?

[David T]

You do that without the engine running right?

Correct, this is a static test. Hard to keep the motor running when you seal the intake.

[Trstno1]

Correct, this is a static test. Hard to keep the motor running when you seal the intake.

haha....right