To all...

I know a little bit about rebuilding engines & tuning them, but this '74 Vette had me clueless as to why I could not get the engine timed and no matter what it seemed to have a vaccum leak that I could not find. Finally I just got fed up with it and had it flatbedded off to a mechanic to see what he could find out. Little did I know, but the headlight that would not actuate on vaccum(raise/lower) was the cause of the engine problems. Had it not been on the list of items for the mechanic to check out I am sure he would still be searching for the problem.

The part? 1968-82 Headlamp And Wiper Door Vacuum Actuator Relay
(Ecklers Pt# A8258) $59.95/per side(L/R)

Napa & GM have obsoleted the part. Guessing these actuators do not go out. Yes they do!

Cheers! So much for projects....

 

Yes... those relays are a source of vacuum leaks (also causes slow headlights) and do go bad..A fairly common but often overlooked problem.

 

Yup, both of my headlight relays were leaking badly when I got my car. I pulled one of them apart and repaired it, then hooked it up to both headlights and shelved the spare. Works! :cheers:

I've seen new relays for $40-$70 :eek: depending on who you order from. (Zip, MA, and Ecklers all carry them) But really the only thing that goes bad on most of them is that little cylindrical rubber seal on the relay's shaft. I'll tell you how I fixed mine if you want to know.

 

Isn't there an inline check valve located close to the carb so this doesn't happen?

 

Hmmmm...this is VERY interesting since I have a headlight that won't pop open and I've been thinking vacuum leak, since my engine runs rough and has trouble idling. What I plan on doing is plug up all the vacuum lines at the manifold with the exception of the vacuum advance line, and see what happens. If it smooths out, then I can connect each line until I find the culprit.

A more expensive alternative is buy a vacuum tester that you squeeze to create vacuum and find leaks.

Dep

 

Auto Zone and a number of other parts stores will loan you the tool for free. You do have to leave a deposit for it.

 

Yep...thought about that, but tools are almost as bad an addiction as Vettes. I hate going to the tool box and remembering that I rented the tool and need to run out and rent it again.

Dep...aka Tim "the toolman" Taylor ;)

 

wcsinx, I'm interested to know what you did . Where did you get the parts and how did you disassemble it?

 

I didn't use any special tools or parts.

What I did was first pry the retaining ring off gently and carefully with a small screwdriver and a pair of needlenose pliers. Do NOT damage this thing.

Then once you have the thing apart you'll see a rubber sort of dumbell shaped diverter seal on the end of a little metal shaft. This is the thing that actually controls whether vacuum is applied to the top of bottom port. If yours is like most others that leak, then it's dried out and shrunken down to the point of not sealing in any direction. What I did to get this thing to seal was ...

1. Took a cotton swab, put a dab of grease on it and work it into the cotton, then use that swab to make a thin film on grease on the inner surface of the plastic tube in which the diverter slides up and down.

2. put a thin bead of RTV around the lower **** of the diverter valve

3. carefully and slowly slide the diverter straight into the tube just until you have the entire **** in and a little bit of RTV squeezes up around the sides

4. Somehow support everything so that the diverter stays straight in the tube, and let it cure that way for about an hour

5. slowly twist and pull the diverter out being careful not to damage the ring of RTV around the **** ... hopefully the film of grease kept it from trying to adhere to the plastic

6. repeat steps 1-5 for the upper **** on the diverter after cleaning any excess RTV from the tube. This time you'll have to slide it farther in (obviously)

7. again clean out the tube as well as any excess RTV from the diverter itself

8. Greased up the tube, slid the diverter all the way in, put everything back together, crimp the retaining back down ... and *poof* my headlights move again. :cheers:

 

Thanks for the tips. I'll have to give that a try. You should add this to the Corvette FAQs it could help a lot of people.

 

I'm getting a little dizzy here! :confused:

The check valve prevents "backwash" but would not help you if you have a vacuum leak around the headlight relay or actuator.

If you had posted your problem and symptoms on the forum I bet we could have sorted it out for you.

As somebody mentioned above, step one (for me at least) is to simply cap off the vacuum source at the intake manifold, usually between the carb and the distributor. That is the source of vacuum for headlights and wipers (if you are pre-73). If engine smooths out then you have a vacuum leak somewhere in the headlight or wiper system. Vacuum for the distributor (and I think in most cases power brakes, but I dont have em) comes off the carb. :) MJ




[Modified by MNJack, 1:47 PM 10/17/2002]

 

How did you get both lights to run off 1 actuator??? One of my lights is slow and the other has been slow but yesterday morning it would not come up, I had to get out and lift the bezel up. I want to "rebuild" the good one (it's slow so it's prolly on it's way to going bad) and hook both lights up to it.

 

Just get two 'T' connectors and a little extra hose. Hook one 'T' up to the top port and the other to the bottom port of your good relay. Then take both rear (red?) actuator hoses and put one on each side of the top 'T'. Do the same for the front (green?) actuator hoses and the bottom 'T'. Finally be sure to cap off the vacuum port on the tank that the middle port of the bad relay was hooked up to.

Oh, also don't forget to remove the tiny little 'T' fitting (and hoses following it) for the small vacuum hose that leads to small brass ports on the very tops of the relays (not one of the 3 big plastic ports). There should be enough slack in that hose to plug it directly into just one of the relays.


[Modified by wcsinx, 7:59 PM 10/17/2002]

 

Thanks!!

 

WCSINX,

Very good information :cheers:

 

Anyone want to buy a *used & leaking* 1968-82 Headlamp And Wiper Door Vacuum Actuator Relay? Just kidding.....

I'm a happy camper just getting the darn thing figured out and since it was already at a mechanic(that requested the part) I wasn't going to cheap-skate it out on getting this thing on the streets. You have to remember that this thing was basically stored the last 13 years... all kinds of stuff don't work when they are not lubricated/actuated for that amount of time. A pretty hefty bill coming tomorrow to change the rear leaf springs & level the rear end... water pump... timing gears/chain... oil pump... oil pan gasket... radiator hoses & alternator belt... harmonic balance pulley... plugs/wires... vaccum problem... & labor for all. Doesn't bother me one bit... it was an open checkbook project.

So be it... I've played the mechanic on 3 other vettes... driving seems like something better to do right now. The crusade of diagnosing/fixing things can be satisfying, but I just don't have the time these days like I used to and it would be a complete shame for such a nice car to just rot even more in another garage.

 

http://iotech.no/corvette/technical/...ight_relay.htm

go to that link ... it's a GREAT tech how to with pics on how to easily rebuild the vacuum relay. I haven't done it ... but others swear by it.

 

Not to beat my chest, but that's actually the first way I tried to repair one of them. It worked, but my headlights moved very slowly because a pretty good amount of air was making it past the o-rings used in that technique. You really need more of a rubber "footprint" in that tube to make an air tight seal that will still move up and down relatively easily. So on the second one I rebuilt, I tried my RTV method, and it worked (sealed) much better than the o-rings. And my headlights now come up in about 2-3 seconds as opposed to 7-8 with the o-ring relay.

There was another method I recall that involved soaking the rubber diverter into some sort of rubber restoral fluid. I didn't know where I could find that stuff though, so I just went with RTV to get the diverter wide enough again.

 

Like some of the others, my passenger side actuator has been naggingly slow even after a rebuild, testing the entire system. I'll have to try the RTV trick along with the bypass test...thanks.

 

WCSINX:
Thanks for the RTV tip ... when I go through my relays, I'll proceed w/ RTV.




[Modified by jackson, 1:55 AM 10/20/2002]