Finding Or Checking A Vacum Leak

[914lps]

The locale auto parts place will loan me a vacuum pump and gauge so I can pull a vacuum on my car and look for a vacuum leak. Do I need to run the engine? I would think not. When I pull the vacuum will a leak anywhere in the engine vacuum lines show up? I know I pull the vacuum, and see if the gauge shows a loss or not. I just do not know if you have to connect it to different areas on the engine, or if you can connect it to any vacuum point.

[VGR]

Vacuum leaks very rarely occur on Asian cars because Asian car makers use extra high quality vacuum hose that dioes not crack or harden for about 15 years.

A big mistake some Asian car owners make is to replace the factory vaccuum hose with auto parts store vaccuum hose. The auto parts store hose is junk - hardens in 6 months and is not metric so it fits either too loose or too tight.

If you are concerned about vacuum leaks and your car is over 15 years old you might consider simply replacing all the vaccuum hoses with factory replacement hose available from Toyota dealers in 3 and 4 foot lengths.

[914lps]

Have you looked under the hood of a LS400? Thats a lot of hose to replace, and some if it is hard to get to!.. Why would I just replace it all becouse I may have a leak? I do know that if i need to replace it, it pays to get the good stuff.

[dpeck]

Have you looked under the hood of a LS400?  Thats a lot of hose to replace, and some if it is hard to get to!.. Why would I just replace it all becouse I may have a leak?  I do know that if i need to replace it, it pays to get the good stuff.

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[dpeck]

Have you looked under the hood of a LS400?  Thats a lot of hose to replace, and some if it is hard to get to!.. Why would I just replace it all becouse I may have a leak?  I do know that if i need to replace it, it pays to get the good stuff.

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What leads you to believe you have a vacuum leak?

[914lps]

Idle surge and before I buy a Idle control valve I want to make dam sure it is not a vacum leak I did not see. Its down to one or the other. Most likly the valve, as I have yet to find a vacum leak, but I have not put a gadge on it yet.

[dpeck]

Idle surge and before I buy a Idle control valve I want to make dam sure it is not a vacum leak I did not see.  Its down to one or the other.  Most likly the valve, as I have yet to find a vacum leak, but I have not put a gadge on it yet.

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with engine running open the hood and spray carberetor cleaner at and around the vacuum lines and connections one at a time when carberetor cleaner is sucked in at vacuum leak the rpm will rise then you will know where the leak is at

[dole2000]

You can use WD40 to do the same drill.

[914lps]

Idle surge and before I buy a Idle control valve I want to make dam sure it is not a vacum leak I did not see.  Its down to one or the other.  Most likly the valve, as I have yet to find a vacum leak, but I have not put a gadge on it yet.

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with engine running open the hood and spray carberetor cleaner at and around the vacuum lines and connections one at a time when carberetor cleaner is sucked in at vacuum leak the rpm will rise then you will know where the leak is at

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Sounds good thank you, but it may not help, becouse the car at idle is surging anyway, so I may not pick up an idle surge due to the carb cleaner being sucked in, as it could be hiden by the idle surge trouble.. I may have a catch 22

[92Lex]

You idle should stop surging if you spray the carb cleaner in the right spot...that's when you know you found the leak. (FYI - It's likely that a vacuum leak will cause your idle to surge)

[maxed_out]

Agree Wd 40 or carb cleaner to find vac leak. Mine did same surge and it turned out to be throttle position sensor. I was lucky just needed to have postion adjusted rather than buy new one. I've seen them wear out and fake out the computer.

[914lps]

Did the carb spray thing. No change to the way the engine was running, so no vacum leak. As i was told before.

The search and work on my Idle control valve goes on. I will try pulling the line from the intake as see if it is sucking air into the engine from the valve. If it is I will see what happens if I choke some air off with my finger. I will also try playing with the idle speed sensor. If it is sucking that means the valve is opening or stuck open??? .. We will see. Still looking for a used one. No one will let me buy one and return it if i put it on the car to test.

[90LS400Lexus]

Oooooo, just be careful with that carburator cleaner on a hot engine, that cleaner is extremely flammable if I recall. :o You probably already know that though, but just a little advice to those that may not.

WD-40 I have heard seems to be the best thing to use.

I have a leak somewhere on my 89 Pontiac wagon, as I can hear air sucking somewhere, but have not had the time to check it. May be part of my low power problem.

Good luck!

Did the carb spray thing.  No change to the way the engine was running, so no vacum leak.  As i was told before.

The search and work on my Idle control valve goes on.  I will try pulling the line from the intake as see if it is sucking air into the engine from the valve.  If it is I will see what happens if I choke some air off with my finger.  I will also try playing with the idle speed sensor.  If it is sucking that means the valve is opening or stuck open??? .. We will see.  Still looking for a used one.  No one will let me buy one and return it if i put it on the car to test.

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