HVAC Issues, Front Hubs?
Thread Starter
|
Fleet Mechanic
Joined: Mar 2004
Posts: 1,483
Likes: 1
From: SE PA
HVAC Issues, Front Hubs?
Hey gang...since my Ex has largely become a garage ornament it doesn't get driven as much.
Since the recent snows, it's been on the road. Everything has worked fine but I noticed an issue a couple weeks ago where it would default to blowing air out the defrost vents regardless of the control ****'s position. This was in normal driving, no 4WD. This seemed to cure itself and did not come back. I assumed it was "lazy" from sitting so long.
In the past two days, I had to move the trailer out of a snowy spot and needed the 4WD as the rear wheels were on ice, the front on pavement. Worked fine again...well, until I returned with the trailer and put it back. Now, it seemed 4WD would not engage the front wheels. I manually locked the hubs and it worked.
I also noticed it was acting funny again with the HVAC.
I suppose since these are both vacuum actuated that they could be related. Anyone have an idea where to start?
Since the recent snows, it's been on the road. Everything has worked fine but I noticed an issue a couple weeks ago where it would default to blowing air out the defrost vents regardless of the control ****'s position. This was in normal driving, no 4WD. This seemed to cure itself and did not come back. I assumed it was "lazy" from sitting so long.
In the past two days, I had to move the trailer out of a snowy spot and needed the 4WD as the rear wheels were on ice, the front on pavement. Worked fine again...well, until I returned with the trailer and put it back. Now, it seemed 4WD would not engage the front wheels. I manually locked the hubs and it worked.
I also noticed it was acting funny again with the HVAC.
I suppose since these are both vacuum actuated that they could be related. Anyone have an idea where to start?
Senior User
Joined: Apr 2009
Posts: 444
Likes: 2
From: Franktown, CO
This is from a 2003 service manual
Hublock Vacuum System Leak Test
****** name=tps_proctitle content="Hublock Vacuum System Leak Test">NOTE: This procedure requires the use of a calibrated vacuum gauge that is accurate to within a minimum of 0.1 in-Hg. It is recommended the Pressure Vacuum Module 105-R0099 or equivalent be used.
You already kow you have a vacuum leak. Hope this helps.
****** name=tps_proctitle content="Hublock Vacuum System Leak Test">NOTE: This procedure requires the use of a calibrated vacuum gauge that is accurate to within a minimum of 0.1 in-Hg. It is recommended the Pressure Vacuum Module 105-R0099 or equivalent be used.
- Make sure hublocks are in the AUTO position.
- Lift and support the vehicle off the ground until the front tires can be spun freely. Refer to Section 100-02 .
- NOTE: The engine is required to be at idle during the following steps to supply the vacuum required for the hublocks to engage and disengage.
Start the engine and allow to idle.
- Turn the mode select switch (MSS) to the 2WD position and wait 15 seconds. If switching from 4X4 mode, wait an additional 45 seconds.
- Disconnect the vacuum line at the right front knuckle and install a vacuum gauge on the line.
- Disconnect the vacuum line at the left front knuckle and plug the line.
- NOTE: Normal operation applies engagement vacuum for 45 seconds and then drops to 0 in-Hg.
Turn the MSS to 4X4 and observe the vacuum reading. The vacuum reading should remain at or above 10 in-Hg for 45 seconds.
- NOTE: Normal operation applies regulated disengagement vacuum for 15 seconds and then drops to 0 in-Hg.
Turn the MSS to 2WD and observe the vacuum reading. The vacuum reading should remain between 5.8 and 7.3 in-Hg for 15 seconds.
- Remove the vacuum gauge and connect the vacuum line at the right front knuckle.
- Turn the MSS to 4X4.
- NOTE: The right front axle shaft and universal joint should turn.
Wait one minute then rotate the right front tire one revolution forward and one revolution backward while observing the right front axle shaft and universal joint.
- Turn the MSS to 2WD.
- NOTE: The right front axle shaft and universal joint should not turn.
Wait one minute then rotate the right front tire one revolution forward and one revolution backward while observing the right front axle shaft and universal joint.
- Install the vacuum pump and gauge line on the knuckle and pump to 20 in-Hg.
- If the vacuum drop is not equal to 0.5 in-Hg in 30 seconds, Go To Pinpoint Test G for further diagnosis of the hublock system.
- Repeat steps 1 through 13 for the LH hublock. If results are not as indicated, Go To Pinpoint Test G for further diagnosis of the hublock system.
You already kow you have a vacuum leak. Hope this helps.
Tuned
Joined: Mar 2006
Posts: 455
Likes: 0
From: Luxemburg WI
Thread
Thread Starter
Forum
Replies
Last Post
SD Rick
1999 - 2003 7.3L Power Stroke Diesel
24
Mar 23, 2016 07:37 PM
flavo
1999 - 2003 7.3L Power Stroke Diesel
32
Dec 30, 2010 10:44 AM
