Used to be a little one, now it's a big one. Follow the troubleshooting instructions found in the sticky section rather than guessing or changing parts and 'hoping'.
1969 vacuum canister issue
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From: Epping NH
1969 vacuum canister issue
Up until a year ago I had strong vacuum to my wiper door and headlights. I had replaced ALL vacuum hoses several years ago as part of a total engine compartment rebuild. I also replaced the headlight actuators and had the original coffee can style wiper door actuator rebuilt.
Last summer I noticed that headlights were sluggish even with engine running and the wiper door was wimpy. I have just got the car out for the spring and the wiper door will not open without me yanking it up by hand. Headlights are pathetic with engine running and unresponsive with engine off.
Back when these things were working, I recall a hiss when the engine shut down which I always assumed was the vacuum tank letting off pressure. There is no hissing anymore and I am beginning to wonder if my tank may not be holding vacuum.
I have heard stories of tanks rotting out from within and filling up with rust / pinholes due to moisture being trapped inside over the years. Can anyone comment about this issue and does anyone know what the pressure at the tank should be with the engine (L-46 350/350) running?
Thanks.
Last summer I noticed that headlights were sluggish even with engine running and the wiper door was wimpy. I have just got the car out for the spring and the wiper door will not open without me yanking it up by hand. Headlights are pathetic with engine running and unresponsive with engine off.
Back when these things were working, I recall a hiss when the engine shut down which I always assumed was the vacuum tank letting off pressure. There is no hissing anymore and I am beginning to wonder if my tank may not be holding vacuum.
I have heard stories of tanks rotting out from within and filling up with rust / pinholes due to moisture being trapped inside over the years. Can anyone comment about this issue and does anyone know what the pressure at the tank should be with the engine (L-46 350/350) running?
Thanks.
Race Director
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The tank doesnt hold pressure, it holds the vacuum generated by the engine. Thus the tank should always have the same vacuum that the engine is capable of generating. Typcially this would be highest at idle. I would try listening for a hiss with the engine at idle to see if a hose has developed a leak or has become disconnected.
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Thread Starter
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From: Epping NH
Fair enough. I can certainly follow the lines since I replaced them all myself years ago along with the check valve. I will get my ear down in there and listen and will report back tomorrow!
Safety Car
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From: Austin Texas
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69 tanks are know to rust and become pinhole cushions,
they are usually so bad you can't blast them or they turn into swiss cheese.could be a leak almost anywhere. but check that tank to ensure it holds vacuum.
Check to see what motor vacuum is with "EVERYTHING" vaccum related Dissconneted.
should be around 12-16" that is your base vacuum.
with the tank isolated it should be able to hold a similar vacuum.
they are usually so bad you can't blast them or they turn into swiss cheese.could be a leak almost anywhere. but check that tank to ensure it holds vacuum.
Check to see what motor vacuum is with "EVERYTHING" vaccum related Dissconneted.
should be around 12-16" that is your base vacuum.
with the tank isolated it should be able to hold a similar vacuum.
Last edited by 69Vett; May 23, 2011 at 04:21 PM.
Team Owner
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From: Westminster Maryland
Hi B69,
Hearing the hiss with the engine running is often a problem.
Many people suggest running a long hose from another car, or vacuum pump, to supply the vacuum to your system in silence, so you can hear even a small leak.
Good Luck.
Regards,
Alan
Hearing the hiss with the engine running is often a problem.
Many people suggest running a long hose from another car, or vacuum pump, to supply the vacuum to your system in silence, so you can hear even a small leak.
Good Luck.
Regards,
Alan
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From: Epping NH
thanks for all the replies
I spoke to my engine guy a while ago and tonite and we are going to run a vacuum pump directly to the tank with the engine off and listen. I'll post results.
Mark
Mark
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From: boston mass
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From: Austin Texas
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"that small cream color connector "
Is in reality the "one valve", to hold vacuum after the vehicle shuts off.
they are plastic and can leak.
Big hose in from carb. is vacuum source, 2 small lines out, 1 to interior,
and 1 to vacuum cannistor.
Is in reality the "one valve", to hold vacuum after the vehicle shuts off.
they are plastic and can leak.
Big hose in from carb. is vacuum source, 2 small lines out, 1 to interior,
and 1 to vacuum cannistor.
Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
Funny this subject should come up. Just late last week I was trying to find a vacuum leak in my '72's headlight circuit. I was absolutely convinced the problem existed in my headlight switch. You guys know the drill: tach cable, speedo cable, steering column etc. Well, after much dis-assembly and checking and checking and checking everything I could think of only to get confusing results, I finally isolated the leak down to the connection between the 90 degree rubber elbow and the headlight over-ride switch that plugs into it. All of that dis-assembly only to find the leak in one of the easiest areas of the vacuum system to repair.
I said all of this to say check the easy stuff first. Even the most simple of connections can have a failure (got any glue?). Your tank should be an easy check if you have a vacuum pump.
Oh yea, if you don't know much about your headlight vacuum circuit (like me) study the diagrams and discussion shown in the headlight vacuum system sticky. It helped me a truck load.
I said all of this to say check the easy stuff first. Even the most simple of connections can have a failure (got any glue?). Your tank should be an easy check if you have a vacuum pump.
Oh yea, if you don't know much about your headlight vacuum circuit (like me) study the diagrams and discussion shown in the headlight vacuum system sticky. It helped me a truck load.
Last edited by mudbone64; May 23, 2011 at 07:50 PM. Reason: I wanted to.
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From: Epping NH
Vacuum tank follow up - test results
Thanks to everyone who weighed in on this yesterday. Last night we disconnected the two hoses to the tank, one at a time, and after clamping the attached hose, we applied compressed air to the tank (no, we did not blast it - we were gentle). You could hear air seeping out of the tank at the bottom. So, it seems as though I need to replace the tank!
Although I have non-power brakes it looks as though I will need to remove the master cylinder to get the tank out. Has anyone done this?
Mark
Although I have non-power brakes it looks as though I will need to remove the master cylinder to get the tank out. Has anyone done this?
Mark
Team Owner
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From: Westminster Maryland
Hi,
Just to clarify...
The cream color connector is actually the vacuum system filter; the one way vacuum valve, (gray metal), with one large hose in, and a large and small hose out, seals the system so the vacuum remains stored in the vacuum reservoir when the engine is shut off.
A lovely conglomeration of parts!
Regards,
Alan
Just to clarify...
The cream color connector is actually the vacuum system filter; the one way vacuum valve, (gray metal), with one large hose in, and a large and small hose out, seals the system so the vacuum remains stored in the vacuum reservoir when the engine is shut off.
A lovely conglomeration of parts!
Regards,
Alan
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From: Epping NH
So.....
In order to drive at night (lights up) it seems as though I could just pull the two hoses from the tank, link them together and bypass the tank entirely until I have a chance to pull it out and fix it properly. I am thinking of running a heavy bead of epoxy along the entire bottom seem to seal it. A buddy runs a body shop and he says he has something that will do the trick.
As for the wiper door, I am good there since I never drive her in the rain. In fact, it has rained every day here for a month and I have less than twenty 2011 miles on her
As for the wiper door, I am good there since I never drive her in the rain. In fact, it has rained every day here for a month and I have less than twenty 2011 miles on her
Race Director
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From: Dayton, Ohio
For the ones with pin holes in the bottom,I've poured everything from Imron to motorcycle tank sealer in them,nothing has failed. 
EDIT- If the leak in the tank is your problem,then Yes you can put the 2 hoses together to make everything work while the engine is running.
EDIT- If the leak in the tank is your problem,then Yes you can put the 2 hoses together to make everything work while the engine is running.
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From: Epping NH
sealer
So, I want to be sure I read that right, nothing has failed, or nothing has worked???
Also, are you saying that you have poured sealent directly into the tank? Sounds easier than pulling it out...
Also, are you saying that you have poured sealent directly into the tank? Sounds easier than pulling it out...
Race Director
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From: Dayton, Ohio
Yes poured it in through a nipple,towel under the tank to catch what came out of the pinholes,waited 24 hours or so and tested,they all held vacuum.
I really didn't expect it to hold for any length of time but it has. I bet I've done that to 6-8 of them. Just the ones though with leaks in the bottom.
I do think an epoxy repair from the outside would be a better repair though.