Vacuum problem, ( ATF contamination )

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Retep
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Vacuum problem, ( ATF contamination )

Post by Retep »

I either have a vacuum problem or the dreaded ATF contamination of the HVAC system.

For the past couple months, with the HVAC control in off position, I have experienced air blowing out of the vents instead of the floor while under hard acceleration such as merging onto the highway. I had this happen a year ago and a quick undo and redo of the “Hot Feet Fix” took care of it. Not this time. :x
The other day, I get in the truck to drive to work, again with HVAC in off position and air is constantly blowing out of the vents as I am driving. I set the control to floor and then defrost with no luck. It continued to blow out the vents. This continued for about 5 to 10 minuets and then cleared up. It is now like this anytime I drive. Air blows out of the vents regardless of HVAC position for about 5-10 min then goes to where it should with only a slight bit of air from the vents. After it clears up, if I accelerate hard, it will go back to the vents again for another 5 minutes.

On top of all this, my front differential no longer engages. :twisted: T-case engages fine but no front diff engagement. I changed the t-case vacuum switch about a month ago because the front diff wouldn’t disengage at the time. There was no sign of ATF contamination in the vacuum lines when I changed the switch.

Do I just have a bad vacuum leak somewhere causing HVAC and front diff issues or am I about bend over for the dealer because of ATF contamination?

Thoughts and opinions appreciated. My love affair with this truck is going sour fast.

Thanks,
Pete

edited title-HJ
[size=75][url=http://photobucket.com/albums/v179/retep910/S10/]2002 S10 Ext. Cab 4x4 Indigo Blue[/url]
Extang Black Max Tonneau, Rubber Bed Mat, Vent Visors, Bugflector II, SilverStar headlights, Dark Window Tint, Disabled DRL, Debadged, K&N Filter, Skid Plates, 1.25" Rear Wheel Spacers, Boise 3 aal kit, mild T-bar crank, Dueler A/T Revo[/size]
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Post by HenryJ »

It does sound like you have a vacuum leak. Crawl underneath and check to see if the tripple line connector fell off of the transfercase switch, since you were recently messing with that. If that is ok, you are just going to have to listen carefully and start checking lines and connections.
Sometimes a long tube can be helpful. Use it to narrow down a location, or check out areas. Check the lines behind the power brake booster. The vacuum reservoir is in the LF , drivers side fender.
Jigg recently highlighted a weak link in his hoses.

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Post by 20Blazer00 »

Also check that the switch connector is oriented correctly, if the lines are not exactly on the way they're supposed to be then it will stop 4x4 engagement. Friend of mine told me he had the switch replaced at local tranny shop and they accidently rotated the lines on the switch and it caused his 4x4 engagement problems, he took it back the shop rotated the lines to the correct positions and fixed that problem...
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Post by HenryJ »

Good point. There is a pin that correctly clocks the attachment. I suppose it might be possible to install the connection incorrectly, however this was designed to make it so that it would only install in one position.

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Post by BADs Crew »

My truck has just developed a vent problem also. I have no air at the dash or defroster vent. The drivers side works just fine.
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Post by Retep »

For kicks I checked the vac lines going to the recently replaced t-case switch. All are in visibly good shape and the key on the switch is in line with the plug.
I did notice some dry rot on the vacuum lines atop the brake booster as Brule mentioned. Those lines look like they run deep into the bowels of the rig. Changing them would not be fun.
I really feel this is a vacuum problem. I don't have the time or the patience to trace and test every vacuum line on this truck, thus I think a dealer visit will be in order. Cold weather is still a few months away so I have a little time.
Brule, where exactly is the vacuum reservoir at? It does not appear to be visible without removing something.

Thanks,
Pete
[size=75][url=http://photobucket.com/albums/v179/retep910/S10/]2002 S10 Ext. Cab 4x4 Indigo Blue[/url]
Extang Black Max Tonneau, Rubber Bed Mat, Vent Visors, Bugflector II, SilverStar headlights, Dark Window Tint, Disabled DRL, Debadged, K&N Filter, Skid Plates, 1.25" Rear Wheel Spacers, Boise 3 aal kit, mild T-bar crank, Dueler A/T Revo[/size]
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Post by HenryJ »

Retep wrote:...where exactly is the vacuum reservoir at?
It is inside the left front fender , right behind the ABS system. You are right, you can't access it. Heck you can barely see it. If you can not hear the leak, and are unable to chase the lines, then some time spent with a hand vacuum pump/gauge will likely be needed to trouble shoot the problem. That would be my guess.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving! - ThunderII KE7CSK
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Post by Daniel »

mine has always had a vent problem, im going to take it to the dealer one of these days when i have money and have them fix it
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Post by Retep »

Update:
A couple of weeks ago, the HVAC control stuck on dash vents. Today I took it to the dealer who confirmed my fear, ATF contamination in the HVAC lines. He said this was also the reason for the front diff engagement issue.

I guess I changed out my T-case vacuum switch to late.

Will have to think long and hard before I ever buy another GM Truck after my experience with this one.

Pete
[size=75][url=http://photobucket.com/albums/v179/retep910/S10/]2002 S10 Ext. Cab 4x4 Indigo Blue[/url]
Extang Black Max Tonneau, Rubber Bed Mat, Vent Visors, Bugflector II, SilverStar headlights, Dark Window Tint, Disabled DRL, Debadged, K&N Filter, Skid Plates, 1.25" Rear Wheel Spacers, Boise 3 aal kit, mild T-bar crank, Dueler A/T Revo[/size]
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