pwsusi

I know there are tons of threads on vacuum leaks, but I've been reading and trying things and I'm at a loss. When I start the car and the wiper door pops and stays open. The headlights will partially come up and then go back down...sometimes one will pop up all the way. I did some initial testing with a vacuum pump to the three actuators, actuator relays and wiper control valve. The control valve was questionable and cheap enough to replace so i did that first which didn't resolve the problem. While I didn't think there was an issue with the actuators or relays out of desperation i then got a new one of each and basically went one at a time replacing the old with the new to try to rule out it being one of those with no success.

So basically i think I've ruled out the actuators, relays and wiper vacuum control switch. I don't hear any hissing in the lines but of course not sure if there's a leak anywhere in those. I did see some people using a vacuum pump to help troubleshoot but don't own one and while i could rent one at this point i'm hesitant to do so if i'm going to end up taking it to the shop after spending all this time and some money on stuff that didn't fix the problem. I'm about to do so but would like to give it one more shot as it will be good to learn something and certainly cheaper to fix it myself. I'm looking for suggestions on how best to troubleshoot at this point. I'm not sure if there's a way to better isolate the problem or work my way out from the engine as opposed to what i'm doing now which isn't working.

Thanks in advance.

pws69

I'm not sure about the terms you are using, but there is a "Check Valve" behind the carb that, when failing, can cause the problems you describe. It has one hose in from the carb and there are two hoses exiting - and the connections are important (not to be switched). Have you addressed this part also?

pwsusi

Thank you. I tested that with the vacuum pump and it seemed to be fine. it's cheap enough maybe i should just replace it...but i have not. I also forgot to mention i got a new vacuum filter. The one that was on there was a bit dirty but not clogged and otherwise seemed to be fine. I replaced it as it was cheap but that also didn't do much

pwsusi

Actually i just confirmed the check valve is not the issue. I have a '71 also (with no vacuum issues) and swapped check valves. This didn't resolve the problem so i think it's safe to say the check valve is ruled out.

pwsusi

ttt

Iceaxe

Block off the wiper door and get the headlights working correctly. After the headlight vacuum system is working add the wiper door back into the system. Using this method I have found takes one big problem and breaks it down to several smaller problems that are easier to solve. I used golf tees to plug the vacuum lines and isolate different parts of the system. Hope that helps.

pwsusi

Thank you, that's a good suggestion.

- To block off the wipers should plug the 4 hoses which are connected to the wiper door relay?
- To block the headlights should I plug the middle one of the larger hoses on both headlight actuator relays? (yellow and green #6 going to the headlight relays in the diagram below

I'm using this diagram as a reference ...

Iceaxe

I pulled the yellow hose off the wiper relay (F) and stuck a golf tees in it. That blocks the wiper control side. I plugged the command side at the tee under the dash by unplugging the wiper side of the tee and installing a 3" section of vacuum line with a golf tee blocking the end.

I used a variation of this method to isolate other sections of the system as required. I just keep shrinking the system until I found my problem and then I added more back into the system and went back to work solving problems. The vacuum system is easy to work on, it just takes time and patience to solve the problems, and my system had lots of leaks.

pwsusi

Thanks again. I was hoping i could block off the wiper door vacuum without having to take apart the dash. I guess nothing's easy

Iceaxe

You don't have to take apart the dash to block off the wiper door vacuum. You block the control side off at the relay mounted to the firewall. You block the command side off by laying on your back under the dash and reaching up and plugging it. My tee was just after the hose passed through the firewall. If it's an AC car (mine is) you have to remove the plastic AC duct under the dash first, but that's easy.

First thing I would do is plug a mity-vac into the command side right at the manifold check valve and see if it leaks. You might get lucky and have no leaks and so you can simply start tracing your problems on the control side and never have to mess with the command side.

After I bought my car I got really good at fixing the vacuum system as just about every component was leaking vacuum. I replaced most the items with cheap Chinese junk and they still leaked. That's when I learned to check new components before installing them and buying quality parts if you can find them is worth the extra coin.

There is nothing hard about fixing the vacuum system, it just takes time, patience and a mity-vac :-)

pwsusi

Thank you. I disconnected the small hose (command side) from the check valve coming from the manifold. I hooked up a vacuum pump up to that hose i disconnected and it doesn't hold vacuum (in fact i can't even get the needle to move). I tried the same thing with the thicker hose (control side) disconnecting from the check valve with the same result. It seems i may have multiple problems.

ramair_bryan

Blocking stuff off is the way to go.
But here's how I roll...…….

I noticed a big leak, but couldn't find it for nothing. Then I pinched off the PVC hose....and watched my problems go away.
Motor idled down nicely, and I could make adjustments with ease.
Turns out PVC valves seem all to be made for FI cars now a days. Relying on the idle air control (computer) .
Not so on our cars. We need our PVC valves to be calibrated like they used to make them.
So now, PVC is a great big vacuum leak.
I picked up a paint gun pressure regulator at harbor freight that has a little dial for adjustment.
Added it in before the PVC valve and presto...minimum vac at idle, and still pull enough for the crankcase.

About finding a leak...
The engine makes too much noise to hear anything, so I run an air hose from my pickups brake booster to anyplace I want to test for a leak on the stingray.
I can hear that hiss well.
A lot like my ex -wife...…………….

Iceaxe

Go to the tee under the dash and you can check the wiper and headlight command side separately. If one side holds vacuum you have just cut your problem in half... see it's simple, just time consuming.

derekderek

Also trim about 3/8ths inch off each hose end you pull-as long as there is enough length to reconnect. But the way everything pops when you start the engine points to control valves not shutting stuff off and the tank leaking empty when engine off.

pltmgr

You are correct about tons of threads regarding vacuum. I recently was successful in getting my headlights and wipers to work correctly on my 68.. I did what Iceaxe suggested- got headlights working and then wipers. Please keep in mind those 50 year old rubber hoses are way past their design life. I tried cutting the tips off these hoses but since they were too brittle and stiff it didn't help much.

pwsusi

Thanks for you input guys. This is all making sense and I finally feel like I'm making progress. Here's where i'm at currently...

I blocked off the headlights by pinching the two hoses that run from the vacuum tank to the center connection on the stem on the headlight relays. Under the dash I also blocked the hose at the T that runs up to the headlight switch. This helped me isolate the wiper door which is where i decided to start.

When I started the car the wiper door was still popping up and with some trial and error found it was losing vacuum at the override switch. There was a rubber piece attached to the override pull down switch with little metal barbs that the hoses connect to. When i went to pull the hoses off the metal barbs came out of the rubber housing, which led me to believe this is where vacuum was leaking from. I eliminated this rubber piece with the barbs altogether and connected the hoses directly to the override pull down switch and now my wiper door opens and closes correctly

I think i have some issues on the headlight side too, but before going there I have a second wiper related problem I want to investigate. When i activate the wiper switch in the center bezel the wiper door doesn't open and the wipers don't run. If i pull the override switch down the wiper door pops up and I'm then i'm able to work the wipers with the wiper switch at the center bezel. I'm thinking i could have a bad wiper solenoid? It's clearly not the wiper motor since the wipers do work as along as i pull the override switch down first. I also checked the wiper fuse and that seems to intact. Wiper door seems to be okay with the override switch so i don't think it's vacuum related.

Does this sound like the solenoid or something else? If the solenoid what's the best way to test it?

Thanks again,
Paul