I've discovered something a little odd on the Vette I picked up. It's an 86 Convertible. I had to replace a coolant hose, so had to unhook a couple other things for ease of access. In doing this, I found that there was already one vacuum line that was unhooked. Weird, I thought. I figured that maybe I'd just bumped it or something, but I can't even find where it's supposed to go. Car seems to run fine without it being hooked up. The only thing I've noticed is that my brakes seems kinda stiff lately, like they're not getting the power in the power brakes. Car idles fine, drives fine, all that (which would be unusual I thought for a car with a huge vacuum leak. I know one thing to try for sure is to see if there actually is any vacuum on this line or not. However, I thought I'd try to see about coming here for some advise. The line comes up from the vacuum canister, to a selanoid (I think), then runs up and under the throttle body (bear with me, I'm probably not using the right terms). It's there that it just ends, without connecting to anything. I've looked over vacuum diagrams and the only thing that doesn't look quite right is the PCV valve. Looks like this was maybe supposed to be T-ed in with another line, but again, can't find it. Would any 86 owners have any advise as to where this mystery line should go? What would be really handy would be right side (passenger) pics of the PCV on the valve covers, as well as a closeup of the throttle body. Any help is appreciated.

Thanks.

 

I'm not sure about the T on the PCV valve but can say that there are two vacuum connections on the TB:
-a large hose goes under the TB to a connection near the breather on the right side
-a small hose connects about mid point under the TB

If that vacuum hose from the canister is about 1/4-3/8" in diameter it likely goes to the right side of the TB. If so there wouldn't be any vacuum on that line and the port on the right side of the TB is likely plugged.

 

That sounds about right. The end on the vacuum line made me think of a spark plug wire at first, and the line itself would be around that same size. There is the larger one on the right side for sure, and it's plugged in, but if the other one is actually UNDER the TB, I'll have to look for it. If you happen to have a pic, that'd be great. I can't get a pic of mine at the moment (at work), but if I can't get it sorted out after work, I'll post a pic of what I've got and we can get it figured out from there. Thanks again for the assist.

 

There's a small hose bib that extends downward from the underside of the TB. You can best see it from standing on the driver's side of the engine; it should be above the area of the thermostat housing.

Jake

 

There are actually two "vaccum" cannisters in the driver's side headlight well.

One is for the cruise control and should have a single vacuum hose running along the fender well toward the firewall and plugs into the servo. It's round. There's a second vacuum hose coming off the servo that goes under the plenum then into a 'T' and then into one of the bibs above the fuel pressure Schrader valve. Check that 'T' because many times it will be cracked from being exposed to years of heat and will leak.

The other cannister is for the fuel tank vent system; that should be the one shaped sort of like a coffee can and it's the one with the solenoid. This is the one that "T"s into the PCV hose on my 86.

I've removed the A.I.R. and EGR stuff from my 86, so I don't have anything plugged into the hose bib under my TB; I have it blocked off.

I've forgotten where all those other A.I.R. and EGR vacuum hoses run, but there should be a diagram either under the hood or in the Shop Manual.

If you need me to look up the hose routing in my Shop Manual, let me know.

Jake


[Modified by JAKE, 2:32 PM 5/26/2004]

 

It sounds like your talking about the Egr vacuume line. The egr vacume switch mounts on the back of the thermostat housing. The egr valve is located under the plenum air box on top of the lower intake about center. I was looking for a link I saved. There was a guy that posted a vacume diagram here that is in the archives. If I find it I'll post the link

 

I found it, check out the diagram and see if this answers all your questions. http://forums.corvetteforum.com/zerothread?id=402086