Was going to start checking for vacuum leaks earlier today because I have been getting some symptoms. So I was using Shoebox's ever useful site to troubleshoot it. I go to find my check valve, and instead i have two nipples and a vacuum hose where the check valve should be. I THINK the vacuum line is connecting the line from the intake manifold to the line for the mode selector. There is no line for the for the vacuum canister as far as I can tell, though in shoebox's picture my intake manifold line looks like his vacuum canister line.

The HVAC system works OK but I lose my 5 top vents (not dashboard) under load, and when switching from my top vents to something which doesn't use use them, I get a long loud hissing noise very evident while riding in the car (stops after a couple of seconds).

So I guess I'm wondering:
1. What the hell is going on with my car
2. If damage can occur without the vacuum canister being hooked up

Thanks for any and all help guys.

 

checked my vacuum canister, and found that the hose was pretty brittle and corroded from battery acid. So I'm guessing that one of the previous owners (or mechanics) took the easy way out and bypassed the canister instead of tracing the problem.

So, I guess I'm wondering what kind of problems this could cause my system (that vacuum canister has to be there for a reason).

 

I had a similar problem, which I just recently discovered thanks to slopokrodriguez.

My check valve was there, but the line goin from the top of the check valve to the vacuum canister was broken in two by batter acid. And yeah, I had the same problems you did - I lost the vents under load.

However, since the line was open, I had a major vacuum leak going into the intake manifold. Once I fixed it, I got a nice boost in torque/sotp, and the brakes felt MUCH firmer.

The check valve should run about $2-3 at a dealer parts store or at autozone. Just pick one up. If you have the nipples and its closed everything off, I think you'll be fine running without the vacuum canister, although you brakes might feel a lot looser under deceleration.

Good luck!

 

Thanks for the reply!

So I guess I'll just pick up a new valve and block off the nipple for the vacuum canister with a vacuum cap (does anyone see a problem with this?). I lost where the vacuum line was going from the canister when it broke off anyways.

 

blocking off the vacuum canister with a nipple won't relaly do anything - since nothing is connected to it, its not going to be holding any vacuum, it'll just sit there.

Just get the valve, reconnect it with the vacuum lines, and you'll be fine.

 

There have been a few people that have removed the check valve when it was broken and temporarily joined the hoses like you found on your car. It won't harm anything as long as your system has no other leaks. You just won't have any reserve vacuum for the vent controls, like you found out under a load. When there is no vacuum, the air defaults to blowing out the floor and defrost ducts, so you will hear/feel a change when you stomp on it or when going up a long hill.

The new check valve with the port to the tank blocked off won't do a whole lot for you, but should make it hold a little vacuum after the engine has been turned off.

 

Ok, so I'll just run completely new line to my vacuum canister from the check valve.

But I have another question. I have a vacuum leak somewhere to my mode selector from my vacuum check valve. I have pulled off the cover under the passenger side dash, and found 6 different colored vacuum hoses that where connected together. When I pulled the connector apart I found what looked like sawdust shavings, but only around the connection to the black hose. So I guess I'm wondering where the mode selector is in the dash (it's not the hvac turn **** switches is it?). And also I'm wondering where all those wires go toward the firewall, and if there's a good was to access them.

 

I have the exact same thing happening with my vents. Thanks for the help. I'll have to go check that out.

 

Damn thats what causes that, I am gonna go check that out.

Thanks

 

Why do you say you have a leak? You know that hissing you hear when you turn the **** is normal, right?

Yes, the **** is the mode selector.

 

I say i have a leak because i put vacuum on the black vacuum hose going to the mode selector from the check valve and it doesn't hold any vacuum, it just leaks out.

Also, when I checked the back of my selector switch on my HVAC controls, I have 7 connections for vacuum hoses, but only 6 of them are actually have hoses connected to them (yellow, green, pink,red, orange, and black).

 

Does it leak no matter what position the selector is in? You may have a bad hose or actuator.

Vacuum Diagram

 

yeah, i tested each of the the colored hoses individually from the blue/green disconnect to the mode selector. Are they all supposed to hold vacuum?

Anyway, the only problem I'm facing is the loss of air coming out the vents during high load conditions. So, if i replace the vacuum check valve and connect up the vacuum canister again, will that fix the problem?

 

Yes, they should all hold vacuum.

That should do it.