Need help troubleshooting 69 vacuum system

[Michael L.]

Guys,

I'm trying to troubleshoot the vacuum system on my newly restored 69 4spd non-A/C car. All the control valves and HL actuators were rebuilt by Bob Demmel. I've read numerous posts on here about this and the first thing I did was go the Doc Rebuild's web site to get the troubleshooting manual and it says he's closed and not taking orders or shipping anything and "may" reopen in August. I then went to MidAmerica's website for their guide and they say it is out of stock. Are there any other alternatives? Also, I have an electrical vacuum pump I can use to test the system but not sure how powerful it is. It's a cheap one from HF. I also have a mightvac hand held piece. The question is, for the electric pump, is it possible that it could be too powerful and damage the car's systems? Thanks for your help.

Mike

[Larry M.]

Re: Need help troubleshooting 69 vacuum system

Electric pump will not damage your system, but the Mighty-Vac is all you really need. Car engine typically generates about 16-20 IN HG vacuum.

I know of no book or procedure for this checkout, but AIM should have a lot of detail that you can follow. Just take thing one hose at a time. DR REBUILD definitely has all the right/correct vacuum hoses and end fittings, but I don't think he has a checkout booklet.

I am helping a close friend restore his 1969 Corvette, and we have been checking things as they go together. Ultimately one needs to finally pull a vacuum on the vacuum tank, and then begin working each item and checking the response. Do one item at a time.

Electrical system is not much different for checkout........except that you can burn thru a wire if you have a ground or cut a wire insulation. I would probably use a 6 volt lantern battery or a small 12 volt drill battery and an inline fuse for final checkout of the electrical wiring. Maybe you are past this stage??

Larry

EDIT: I just read the DR REBUILD old catalog from 2008 on vacuum hoses etc and he does list a booklet for troubleshooting. This is probably what you were referring to. He states that Zip (his arch enemy) also sells this book for more money. So if DR is closed, try Zip and see if they have this booklet available.

[Michael L.]

[David M.]

Re: Need help troubleshooting 69 vacuum system

What is the actual problem? Whats not working?

[Tom R.]

Re: Need help troubleshooting 69 vacuum system

You don't mention whether the wiper door relay was rebuilt but did you have a schematic to show the correct routing of vacuum hoses?
I've used the attached in the past to troubleshoot and found it helpful. Have the Zip book but these are better.

HeadlightVacuumTutorial.pdf
Vacuum Troubleshooting 101.pdf

[Michael L.]

[Joseph S.]

Re: Need help troubleshooting 69 vacuum system

Michael, Before you get into the system, please block off the tank fittings for the Headlight hose and the Wiper hose and make sure that your tank will hold a vacuum. I have seen many with small cracks that cause a lot of aggravation while trying to troubleshoot!

[Michael L.]

Re: Need help troubleshooting 69 vacuum system

thanks Joe will do.

[Mark E.]

Re: Need help troubleshooting 69 vacuum system

The best illustrated schematics of the vacuum systems I've seen are on WillcoxCorvette.com.

They show both headlight and wiper door systems, and there are separate schematics for 68, 69R, 69L, and 70-72.

Beware: The vacuum schematic in the 1970 shop manual (and maybe other years also; I haven't looked) for the control system is wrong. It was frustrating while I figured that out.

[Mark E.]

Re: Need help troubleshooting 69 vacuum system

Regarding vacuum pumps:

Hooking up an electric vacuum pump is a great way to test the entire system. With the engine off connect the vacuum pump using a long vacuum hose so it can be located outside the garage. This makes it quiet enough to hear leaks. Then isolate leaks using a pair of hose crimps (e.g. mini vice-grip wrapped in tape to protect the line).

I use a MityVac mostly to test individual components.