various vacuum problems

[denver_blazer]

I've owned my blazer ('94, 4.3 cpi) for a little over a year now and even though it seems to have been taken care of pretty well before I've had lots of problems. (heater core, oil cooler lines, power steering hoses, fan switch, trunk lock and egr)
I've been able to fix all that so far, but there's still a bunch to be done.
My question:
Whenever I accelerate or drive the truck under high load, my vents switch from the vent setting to the defrost. As they are vacuum-operated, I have a feeling that my intake vacuum is too low. What should it be?
Also, what kind of performance can I expect from the brakes on the Blazer? I have owned two BMWs prior to the truck and they definitely had better brakes, so I wonder what I can really expect.
Thanks!

[ctesla]

welcome to AF!
...and I wish I was back in Colorado right now...
currently working on an experimental engine; in Houston, AARRGGHH, the humidity!
anyway, the heater doors are vac operated by a switch behind the dash, kind of near radio and glove box (above evap) area.
it could be the switch losing vacuum, or a hardened line leaking or cracked. I will check my service manual when I return to my shop in a couple of hours (came home to eat)
as to your brakes; go to AutoZone (even though I do not like some of their components, or most of their customer service protocol) and get the Carbon Metallic/Fiber (I think your's will be part#0154 or 1154 something like that) for about $40-50.
if they stop an Indy Car @212mph, they'll stop your truck.
personal attestment: in Colorado Springs, on Cimarron(US24), a 3/4ton Dodge Magnum decided to fly into the turn lane behind me at 40+.
I rammed both feet on the brake, pushed down with feet and pulled like hell on the steering wheel, and told my daughter (in pass. seat) to sit fully back in her seat, all while watching this moron in my rear view careen(sp?) into my rear end... I was 2-4 ft. behind the car in front at the light. I never touched his front bumper.
$1000. damage to my rear end, and I drove away... Dodge plastic wannabe tank had to be towed as whole front end gone, radiator in two, wheel and idler bent, both headlights laying 20 ft in front of MY truck when they sailed past my mirrors.
I was disappointed my truck was banged, but I was loving it when the el paso cty sheriff was writing it up going, "Your little truck did THAT to HIS?!?!" It was worth it. bought one new tail light, threw a chain around a tree, yanked the bumper semi-straight (to at least hook-up a trailer), and kept the change.
rear shoes: 186+K still OEM from factory.

...back to you: if you want a vacuum schematic, I can scan it and email you (or fax) in a day; let me know.
good luck,

chris
nrt racing
713.933.5773 (7A-10P central)

[denver_blazer]

Thank you so much for your help! I have taken a look at the vacuum switch, couldn't find any problems there. Do you think it's possible that the overall vacuum is just not 'high' enough?
As for the brakes: I just replaced pads, but I didn't go for the good stuff. It almost feels like the pedal is too hard to push. It was really bad one time when the egr got stuck open. How can I check my vacuum?
As for the vacuum diagrams:
I do have both the Haynes and Chilton manual, but I don't think they include vacuum diagrams for the heater and 4WD. If you could email it, I would really appreaciate it!
I think the Blazer is really a pretty solid truck, just has a lot of small quality issues. None of the vents in the dash are adjustable anymore, they all have cracks and the adjuster levers are broken off.

[OverBoardProject]

Unless they changed the cam it's highly unlikely that you have a vaccum issue in the manifold.
Although this would explain your brake problem.
If the engine doesn't sound it probably doesn't have a cam.

Your S-10 brakes should be good, although probably not as good as a BMW.
Even with the extra weight of 4wd I'm confident that I could shatter that Dodge like ctesla did.

ctesla I like tha sound of your job. I hope that the engine is a big improvement over the present ones.

[Fireplug]

What you have is a common gm problem. Most times it is the vacuum actuator that is bad or a pinched/broken/split vacuum going to it.

[ctesla]

Originally Posted by OverBoardProject

Unless they changed the cam it's highly unlikely that you have a vaccum issue in the manifold.
Although this would explain your brake problem.
If the engine doesn't sound it probably doesn't have a cam.

Your S-10 brakes should be good, although probably not as good as a BMW.
Even with the extra weight of 4wd I'm confident that I could shatter that Dodge like ctesla did.

ctesla I like tha sound of your job. I hope that the engine is a big improvement over the present ones.

within the next three years, if it come outs good;
we've decided for it to go public domain.
NO COPYRIGHTS! no corporate lockdowns.
this will be shared knowledge, and your average race shop will be able to retool, and rebuild for you a 350" with 350HP and get 30+mpg.
our biggest hurdle will be emissions (not environmentally unfriendly, on the contrary, VERY clean, BUT not within GOVT parameters)
I'll try to post (webhost then link)some emission data before and after some initial mods; you'll see WITHOUT the emissions components on the vehicle, she ran WAY cleaner, but somebody says you NEED those money making, engine lighting, code tripping,---
I digress; this is why we're here, to figure it out.

[denver_blazer]

ctesla, I tried to email you, but it just won't go through!
Anyways:

Thank you so much for all this information!

Please, don't worry about those diagrams too much, it's really not that big a deal! My HVAC works satisfactory, it was more something I wanted to know and possibly fix.

When I talked about the vents being broken, I only meant the plastic adjustment things at the outlet. I really don't have a problem with the cold air switching from the dash vents to the defrost whenever I accelerate. As my A/C was not working when I got the car (had to be recharged, I converted it to R-134a) I'm not sure whether it had these problems before. I assume it did, but as I said, it's aminor inconvenience, at least compared to a bunch of other stuff I need to do (especially the rattling back gate!).

I will check inot the cam issue, but more out of interest than anything else!

Once again, thanks a lot for all this help, I really appreciate it!

Gunther