88 Shelby TII vacuum questions..

[wolf_walker]

This is for a friend that has aquired this fine little car, we did some poking around and have a question or two.

Couple of symptoms: On boost the AC vents loose vacuum. And the cruise control is unreliable, it's vacuum related.

We went through using the hood sticker and the factory manuals and replaced and re-routed the vacuum lines. The only thing it has going on there that I question is a line coming from the intercooler hose at the turbo, up to the airbox where it T's to a tiny bleed orifice, this is also plumbed into the line going to the cruise servo. This seems odd, and I find no reference to it in any manual. Does this car not have a BOV or CBV, is this something in place of it? It's on the pressurezed side of the turbo. I also don't see ANY of the orifices listed in the diagram in the system, just check valves.

Does this car not have a vacuum resouvour for on-boost conditions? Does it use the brake booster as such? I know the HVAC flaps have a good leak, but it's not so much they don't function at all, with no resouvour though I can see this being a problem under boost.

We've seen several differing, legitimate mopar, vacuum diagrams, assuming we ought to go by the one on the car as a final word?

And what is max normal sustained boost anyway? I'm aware of the ten seconds of transient higher than normal boost, but flat out seems to be about 9psi if you trust the gauge. The car is a lot slower than I figured it ought to be.

Thanks for any info..

[mmtphoto]

I have an 88 shelby z and am trying to get vacuum hoses correct and have a similar situation with the hose going to the servo and the one going to the airbox from the turbo-there is not even a reference to the turbo hose to airbox on my underhood sticker. I did find this diagram and I think it is probably better than what my setup is:

http://www.turbododge.com/dodge_pict...php?i=1850&c=9

to the best of my knowledge, these do not have a BOV, and I am pretty sure that the brake booster takes care of vacuum needs. When I first got this car (off the showroom floor, new in the Fall of 87) it ran 12 lbs boost, and with a bleeder valve I could get it near 15-It sat in my garage for 4 years until a couple of months ago because the turbo had to be replaced. Over the years, I had replaced vacuum hoses and it is not set up like it had been, so I am also trying to understand how it is supposed to be done. I now have it to the point where it is boosting about 14 lbs again(boost controller), and the cruise is working like it should but it is hooked up to the brake booster only, no check valves.

My AC needs to be drawn down and refilled since it has been sitting so long, but my HVAC functions/flappers seem to be working properly. I figured I was going to use the above diagram, especially the circuit for the turbo nipple/airbox/servo and see if I can get it to the point where it boost 12 lbs without the boost controller hooked up.

Hope this helps, I am going to watch this post too to see what others have to say about this-I do still have a check valve but it goes to the vapor canister, so I went to a junk yard last week to see if I could find any more or office tubes and did get a few check valves.. no orfice tubes however.

[spike]

hi i am have the same thing happen to me did you finded some outer suite? for pic's

[NAJ]

The system does not use a vacuum resovoir, it uses 1 way check valves so your problem is a vacuum leak or faulty check valve.
Check manifold vacuum at the engine and then remove the control head and place a vacuum gauge in the vacuum inlet port to the control head and check vacuum, is it reading the same? If not repair the vacuum source to the HVAC system. With the gauge still connected check vacuum at different conditions,if vacuum falls off the problem is in the check valve or vacuum lines under the hood. If vacuum holds the problem is in the interior with the vacuum actuators/lines/control head.

[GLHNSLHT2]

odd that the vacuum diagram shows a BOV. The T2's never had a BOV.

[NAJ]

That came from Alldata and as you can see it is the official Chrysler diagram. The part # should match what is under the hood.
Here is what they show for an 88 T-1.

[GLHNSLHT2]

I see that it came from Alldata. Just odd though. Gary D's site has the same diagram. I have no doubt it's official or not. But T2's don't have a BOV. Or at least everyone I've talked to backs that up, and the one's I've seen have never had one. The only T2 setup I've seen to get a BOV is the 89 Maserati TC.

[wolf_walker]

Note on the diagram seems to say air shutoff valve, which I assume is the BOV, is only used on auto trans models. This one is a 5spd. The underhood diagram is still present and shows no air shutoff valve, nor does it show the circuit from the turbo intercooler hose to the airbox, I'm suspecting at the moment the manual trans car's did not have this.


So no vacuum reserve, does this mean it's normal behavior to loose cruise or vent control after prolonged sustained boost? The car seems to stay in boost more often than not on anything other than absolute minimal throttle/cruise situations. Or is there supposed to be enough reserve capacity in the HVAC and cruise systems to maintain themselves for a bit of time? Seems an odd way to do things.

Thank you all for the replys.

[winc]

It's my car he's mentioning. I bought it a week ago today. It runs okay, but doesn't have near the power it should. I know one check valve is bad (HVAC from brake booster), which will be getting replaced today.

The problem we're finding is that there are several vacuum diagrams for this year. While the one previously pictured is #4300657, mine is #4300658 (pictures follow - sorry about the poor quality... the label is pretty weathered for 20 years of age)



edit: it is a 1988 Shelby Z Turbo II 5-spd


Thanks again for the the help & replies.

[Screamin4banger]

Quote:

Originally Posted by wolf_walker So no vacuum reserve, does this mean it's normal behavior to loose cruise or vent control after prolonged sustained boost?

I think if you read over NAJ's posts, you'll see he answered you question, for the most part. You even admitted there was a vacuum leak in the a/c system.

If you look at the diagrams for the a/c controls you will see a check valve. When the system is not leaking, I can vouch that the system will hold vacuum VERY WELL. IE: car turned off after driving... sit in car for a while... decide to futz with the a/c controls for some reason... hear 'whoosh' and hear the flapper doors move.

As far as cruise... I never use cruise

[GLHNSLHT2]

Beautiful car.

[winc]

^^ Thanks.

I don't think it has an HVAC leak. I believe the problem lies in the check valves. Last night, we found one wasn't working properly, would not block flow either direction. Today, TWO of them are allowing flow both directions. I picked up a the only one Advance had, then the only one AZ had, and one I found in "spare parts" that came with the car. The two I purchased today are much smaller, had to splice in other hoses & fittings to make them work.

Now, the HVAC is blowing colder at idle and will hold in PANEL for about 3-5 seconds before going to floor & defrost on accel, cruise will disengage after about the same duration. Everything is connected per the car's diagram and I can't find any traces of leaks. Could the under-sized check-valves be the issu0e? May see about getting new ones from the dealer, replace them all since they seem to be going bad.

[spike]

hi sweet ride i has a red one with a gray inside could me how i could put some pic's of my car on here ty.

[NAJ]

I am not sure of the vacuum diagram under your hood or the one's listed in Alldata.
I just searched thru 87, 88, 89, AG/AJ/AP turbo and the only one close to yours in Alldata is a diagram from an 89 AG 50 states emissions.
I ran a parts inquiry on the label part # and it says year in 1988/year out 1988 so.....
Hopefully somebody with an 88 will check thier car and help out.
As far as weather the HVAC and cruise hold vacuum at sustained boost I do not know. the longest I have had sustained boost was 15.60 seconds and all accessories were off.

[wolf_walker]

Quote:

Originally Posted by winc ^^ Thanks. I don't think it has an HVAC leak. I believe the problem lies in the check valves. Last night, we found one wasn't working properly, would not block flow either direction. Today, TWO of them are allowing flow both directions. I picked up a the only one Advance had, then the only one AZ had, and one I found in "spare parts" that came with the car. The two I purchased today are much smaller, had to splice in other hoses & fittings to make them work. Now, the HVAC is blowing colder at idle and will hold in PANEL for about 3-5 seconds before going to floor & defrost on accel, cruise will disengage after about the same duration. Everything is connected per the car's diagram and I can't find any traces of leaks. Could the under-sized check-valves be the issu0e? May see about getting new ones from the dealer, replace them all since they seem to be going bad.

I couldn't pull a vacuum manually on the HVAC line, I still think you have a flap or switch leaking in that end of it. Still need to take a minyvac and check each system independantly for vac integrity, they should all hold for awhile, and I betcha they don't.

Least it's not a Porsche.