jonny4523

I have been working on the vacuum system for months now, and I just found the problem tonight. I have already installed all new vacuum hoses and was about to spen $160 on new relay valves. But then, with the engine running, I unplugged all the hoses and felt them, to check for vacuum. I noticed I was getting extremely poor vacuum from the hose coming from the vacuum reserve tank. (in the 77, its practically to whole front bumper). Then I unplugged the source hose going into the tank and I had great vacuum. So I hooked the source line directly to the relay valve and my headlights worked!!!!!

This is my question. Would it be ok if I were to split the source line and connect it directly to my relay valves, completely ignoring the reserve tank? If I remember right, the reserve tank is only there to supply vacuum to the system with the engine is off. Could I just ignore it?

jonny4523

no vacuum experts?

Graemeinvette

Why dont you fix/replace the vacuum tank and do the job properly?

jonny4523

because you cant. it is incorporated into the bumper. to fix or replace it you have to remove the whole front clip. Or you can but two '80 replacement canisters. But I'm a freshman at Rose-Hulman and am a little short on money. So I see the easy fix out...for now. Do I really need the vacuum tank if I dont use everything while the engine is running?

jerryp58

From what I've read in the past, the answer to your question is YES.

When you have the opportunity, you may want to check the "tank" for pin holes or cracks that may be able to be welded.


[Modified by jerryp58, 6:45 AM 6/20/2003]

pws69

The problem is that you ARE using everything when the engine is running. In a total vacuum system (like we have), "vacuum device on or off" has nothing to do with using or not using vacuum - both conditions use vacuum. Stated simpler, vacuum opens, vacuum closes, AND vacuum CONTROLS. You need the tank to maintain a steady vacuum state. If you remove the tank, I believe your headlight doors and wiper door will constantly go up and down while driving because of the imbalance caused by acceleration (lack of vacuum) and deceleration (high vacuum) - regardless of what position the "switches" are in.

You should fix or replace the vacuum reservoir!

mrvette

jonny, given your financial circumstances, either find the leaks in the rusty tank/frame member, repair with some epoxy, OR, simpler yet, just run it directly and forget about the tank completely, i'ts not all THAT critical to the system...the lack of holding ability IS though, what happens is a continuous vacuum leak, bad for engine operation.....

GENE

jonny4523

I'm sorry. You misunderstood me. I meant that I do not use anything while the engine is off. I am always using stuff (the headlights) while the engine is on. I thought that the only reason the tank was there was to supply vacuum so that the lights while still move up and down while the engine was off.

PRNDL

You can bypass the vacuum tank!

After you shut off the engine you will not be able to raise (or lower) your headlights. I believe the vacuum tank is supposed to give you one cycle of opening/shutting the headlights with the engine off. The only really practical use for this is to lower your lights if you forget to shut them off BEFORE you shut your engine off..... no big deal, right?

With the engine running, you may find the headlights rise very slowly if you are at WOT :lol: . I think you will be hard pressed to notice any difference with the tank bypassed. I dont think your headlights will be popping up and down... try it and let us know. :) MJ

NHvette

You should be fine - T-ing it off. There should be an inline check valve
somewhere. If this is in place, then variations of vacuum pressure should go
unnoticed. Unless - like MJ says, you want to raise/lower the headlights while
under WOT .

:seeya