Heater Vac lines.
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Elder User
Joined: Dec 2006
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From: Kitchener,Ontario,Canada
Heater Vac lines.
I Have a Question ?
Does the vacuum system which operates the heater controls, heater bypass valve etc, potentially cause an intake leak if you have a disconnected pipe or line ?
Not sure if the engine intake is where the vacuum is generated from ? I recently disconnected my cracked cooling bypass valve & removed the vacuum line but it was left open, (I never thought to block the line, but I have now). Could this affect fuel metering due to un-metered air in to the intakes? I've noticed an increase in Gas consumption just lately which could also be due to colder air temps...... but a vac leak could also do this? There is vacuum with the control set to OFF & to A/C ON. This is when I'm thinking fuel mixture could have been incorrect due to the open vacuum line.. Does not seem to affect idle speed if I plug/open the vac line & play with the heater controls.
Don't have any DTC's, MIL is off.
Aeroman.
Does the vacuum system which operates the heater controls, heater bypass valve etc, potentially cause an intake leak if you have a disconnected pipe or line ?
Not sure if the engine intake is where the vacuum is generated from ? I recently disconnected my cracked cooling bypass valve & removed the vacuum line but it was left open, (I never thought to block the line, but I have now). Could this affect fuel metering due to un-metered air in to the intakes? I've noticed an increase in Gas consumption just lately which could also be due to colder air temps...... but a vac leak could also do this? There is vacuum with the control set to OFF & to A/C ON. This is when I'm thinking fuel mixture could have been incorrect due to the open vacuum line.. Does not seem to affect idle speed if I plug/open the vac line & play with the heater controls.
Don't have any DTC's, MIL is off.
Aeroman.
Lead Driver
Joined: Sep 2003
Posts: 7,018
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From: SoCal
Yes, it's the same vacuum that comes from the intake manifold, but it would be a very small leak. That line has a very tiny inner diameter, so its effect is very minimal.
I drove for a couple of years wth one of the lines partially chewed through by rodents. I didn't notice it until the leak got so bad that all I had was defrost, regardless of where the plenum setting was. Even then, I didn't notice anything wrong with the way the engine ran.
I drove for a couple of years wth one of the lines partially chewed through by rodents. I didn't notice it until the leak got so bad that all I had was defrost, regardless of where the plenum setting was. Even then, I didn't notice anything wrong with the way the engine ran.
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Joined: May 2003
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I had the exact same thing, only it wasn't a rodent, but a small front end smash that dislodged the vacuum line just enough to only have Defrost. The engine ran fine, until I really developed another vacuum leak, I never bothered solving this one.
Now, I know that with the slight leak, the old girl was definitely lacking in power - something I put down to it's age (300,000 kms +) but with a good mechanic redoing all the vacuum lines, it runs better than ever now.
Now, I know that with the slight leak, the old girl was definitely lacking in power - something I put down to it's age (300,000 kms +) but with a good mechanic redoing all the vacuum lines, it runs better than ever now.
Thread Starter
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Elder User
Joined: Dec 2006
Posts: 830
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From: Kitchener,Ontario,Canada
I could not really tell any problem with the engine, although I did have a misfire which was caused by worn plugs, that misfire was most noticeable with a cold or damp engine & under normal acceleration at lowish engine revs.
The way I found the leak was I could hear a slight hissing noise at the heater control dial (the heat diverter/selection ****). I eventually tied this hissing noise to the bypass valve vac line, which I had previously had connected up to the broken bypass valve , just laying there. However I recently removed this since I was getting some enquiring looks from the oil change crew. Shortly after that I noticed the hissing sound. Glad I turned the radio off now. Good practice I find to listen to the engine at least once a week to notice if there are any "different" or new sounds.
My engine has also recently surpassed 300,000 kms. During 5000 kms oil change it uses about 1/8" of 5w30 oil, not bad for such mileage.
ATB Aeroman.
The way I found the leak was I could hear a slight hissing noise at the heater control dial (the heat diverter/selection ****). I eventually tied this hissing noise to the bypass valve vac line, which I had previously had connected up to the broken bypass valve , just laying there. However I recently removed this since I was getting some enquiring looks from the oil change crew. Shortly after that I noticed the hissing sound. Glad I turned the radio off now. Good practice I find to listen to the engine at least once a week to notice if there are any "different" or new sounds.
My engine has also recently surpassed 300,000 kms. During 5000 kms oil change it uses about 1/8" of 5w30 oil, not bad for such mileage.
ATB Aeroman.
