vacuum solenoid failure rates?

[Jack]

16790
I replaced a bad vacuum solenoid a few years ago.
It had a big vacuum leak around the electrical connection, plus the posts would barely register as common.
Now a similar thing has happened again.
It has a small vacuum leak around the electrical connection, plus the posts don't register as common at all.

First, the posts should register as common correct?
Second, how many other people have had problems with the solenoid developing vacuum leaks within a few years time?

[David T]

Elaborate on what you mean by "registering as common" on the electrical posts. The leak can be sealed with some silicone, does the valve still work? Is the wiring on the car correct?
David Teitelbaum

[Jack]

By common I mean set the volt meter to test a complete circuit. When I test the solenoid out of the car the two post do not "beep" mean their is a break somewhere inside beyond the two post. To me it seems it sound be a complete circuit inside?

[galbiati]

By common I mean set the volt meter to test a complete circuit. When I test the solenoid out of the car the two post do not "beep" mean their is a break somewhere inside beyond the two post. To me it seems it sound be a complete circuit inside?

Doesn't there have to be vacuum to activate the switch?

[Ron]

Yes the two terminals should have continuity.
if you apply 12V to them, you should hear it click as the valve moves...(it really don't matter which is +/-)

[DMCMW Dave]

Doesn't there have to be vacuum to activate the switch?

No. The switch is electric and turns vacuum on and off.

[DMCMW Dave]

By common I mean set the volt meter to test a complete circuit. When I test the solenoid out of the car the two post do not "beep" mean their is a break somewhere inside beyond the two post. To me it seems it sound be a complete circuit inside?

There is some resistance to the coil, so it may or may not be low enough resistance for your particular meter. I agree with recommendation to apply 12V to the terminals and see if it clicks, and then test it with one of those small hand vacuum pumps to see if it is switching the vacuum (no power = vacuum open, powered = vacuum cut off). Pretty low failure part other than leaking around the terminals. I've seen one short out internally, which does really bad things due to what else is on the same fuse.

[Bitsyncmaster]

I think the vacuum ports should only go one way. From memory, think there is a vent on one side.

[Jack]

Took it off the car again.
Jump the pin with 12 volts heard a click check the valve it was closed, minus leak at the connector. So I have sealed the entire top with silicone.
Ill test again tomorrow to make sure the vacuum is solid.
The internal resistor mention must be what caused my netter to not register continuity.
Thanks for the help everyone.

[DMCMW Dave]

The little cap at the pointy end is the breather so don't seal that one.

[Bitsyncmaster]

Took it off the car again.
Jump the pin with 12 volts heard a click check the valve it was closed, minus leak at the connector. So I have sealed the entire top with silicone.
Ill test again tomorrow to make sure the vacuum is solid.
The internal resistor mention must be what caused my netter to not register continuity.
Thanks for the help everyone.

I never use the meter "buzzer" setting unless I'm just ringing out a harness. Some may be set to 10 ohms or less to buzz and other meters may be 50 ohms.

[Ron]

I never use the meter "buzzer" setting unless I'm just ringing out a harness. Some may be set to 10 ohms or less to buzz and other meters may be 50 ohms.Same here.
...for the reasons mentioned, they may sound off on a circuit that can't handle enough load to burn a mini lamp, lol. Not to mention some are hard to hear...

[David T]

When reinstalling the solenoid it doesn't matter which way you put the electrical plug on but it DOES matter how you hook up the vacuum hoses. As mentioned, one side has a vent to release vacuum when deenergized. Follow the diagram on the engine cover or look in the Workshop Manual. When using the sounding function on a continuity scale on your meter you must always be aware they won't sound if the continuity is more than a few Ohms. It is basically only for a direct wire connection, not for coils or other devices. Even a good bulb my not make a sound. Depends on the meter of course.
David Teitelbaum

[Rich]

A confirmation and review of the info in this old thread along the lines of the DIY repair Jack describes:

A diagnostic intake system smoke test on our car over at mark w’s place last weekend showed smoke coming from somewhere on the vacuum solenoid. He thought it came from the electrical fitting on the valve. The vac solenoid on this car is the original.

Back home I removed the vac solenoid, its connector and its hoses noting which hose went to which port (see emissions label on engine cover for confirmation) and not worrying about the electrical connector polarity as mentioned in this thread.

Tests with the valve out of the car using a 12V power supply, a brake bleeder pump/gauge and hoses/plugs (no smoke machine):
1. Verified clicking sound when 12V was connected-disconnected at the two small male spades (PASS)
2. Center port held vacuum with valve activated/closed and outer port (distributor advance) open (PASS)
3. Center port didn’t hold vacuum with valve deactivated/open and outer port capped closed (FAIL) - consistent with the smoke test.
4. With outer port still capped and valve deactivated a soapy-water leak test showed bubbles at/around the electrical connector while lightly blowing into a hose to the center port proving the seal at or around the elec connector had failed.

DIY remedy (backup remedy = replace the valve)
1. Prepped the face of the valve and the electrical connector base with a wire brush and parts cleaner plus an alcohol wipe.
2. Applied silicone sealant where the connector base meets the face of the valve. Also sealed the small gap between the two raised black plastic connector bases.

After the silicone cured I repeated tests 3-4 to verify PASS, then reinstalled valve. Noting this story is in line with DMCMW Dave's info about valve failure rate and failure mode. Also sending a shoutout to mark w for the helpful diagnostics and advice!

[Helirich]

A confirmation and review of the info in this old thread along the lines of the DIY repair Jack describes:

A diagnostic intake system smoke test on our car over at mark w’s place last weekend showed smoke coming from somewhere on the vacuum solenoid. He thought it came from the electrical fitting on the valve. The vac solenoid on this car is the original.

Back home I removed the vac solenoid, its connector and its hoses noting which hose went to which port (see emissions label on engine cover for confirmation) and not worrying about the electrical connector polarity as mentioned in this thread.

Tests with the valve out of the car using a 12V power supply, a brake bleeder pump/gauge and hoses/plugs (no smoke machine):
1. Verified clicking sound when 12V was connected-disconnected at the two small male spades (PASS)
2. Center port held vacuum with valve activated/closed and outer port (distributor advance) open (PASS)
3. Center port didn’t hold vacuum with valve deactivated/open and outer port capped closed (FAIL) - consistent with the smoke test.
4. With outer port still capped and valve deactivated a soapy-water leak test showed bubbles at/around the electrical connector while lightly blowing into a hose to the center port proving the seal at or around the elec connector had failed.

DIY remedy (backup remedy = replace the valve)
1. Prepped the face of the valve and the electrical connector base with a wire brush and parts cleaner plus an alcohol wipe.
2. Applied silicone sealant where the connector base meets the face of the valve. Also sealed the small gap between the two raised black plastic connector bases.

After the silicone cured I repeated tests 3-4 to verify PASS, then reinstalled valve. Noting this story is in line with DMCMW Dave's info about valve failure rate and failure mode. Also sending a shoutout to mark w for the helpful diagnostics and advice!

That's some good info, Rich. I think you should post that in the "how to" section. Im courious about your smoke test. I assuming a machine generates smoke and pumps it in the intake? Or is this a more home made tool?

[David T]

A "smoke machine" is now a standard diagnostic tool in many automotive shops. Only way to test the evap system on new cars when they have a problem. It is a pump that generates smoke at a set flow rate and pressure so you can visualize even small leaks. It is also very handy to find leaks in induction systems like the one on a Delorean. With it you can find leaky injector seals, gaskets, hoses, missing bolts, all kinds of leaks. On one car someone used a bolt that was WAY too long on the front right of the intake manifold for the ground wires and bent the plug on the end of the runner creating a big vacuum leak. Because you can't see that area the only way you could have found it without a smoke machine was to take the manifold off and examine it. On another car all the smoke poured out of the left rear pontoon. Upon inspection the hoses were there but nothing else. On another car the O ring was missing on the cold start valve. To use a smoke machine I hook it to the small hose off the air filter and plug the intake to the air sensor. After a minute or 2 you can see the previously invisible leaks. The most common ones are injector seals. They get hard and don't seal well. Adjusting the mixture screw to compensate for the leaks only works at idle and even then it doesn't fix the real problem.

[Rich]

That's some good info, Rich. I think you should post that in the "how to" section. Im courious about your smoke test. I assuming a machine generates smoke and pumps it in the intake? Or is this a more home made tool?

Glad you liked that post. A version of it is now here in the How To section (http://dmctalk.org/showthread.php?18945) of the forum.

You can test your vac solenoid valve off the car if you suspect an issue with it or just want to verify it's OK. No smoke needed for that. See the How To link.

In my case the smoke test found two leaks I didn't know about, the other one being at the top of the idle motor.

mark w's "smoke machine" is a Redline professional unit similar to those David T describes, not a homemade gadget. His runs off of internally down-regulated compressed air - no pump. It's this kit or one a lot like it... (https://redlinedetection.com/collections/smoke-pro/products/smoke-pro-total-tech). A real nice setup. Thanks again to Mark.