Two weeks ago on my way home from work I noticed my heat was on defrost regardless of knob position.  I also noticed CC was out as well as 4wd.  The next day everything was back to normal.  Today the wife and I went to lunch and no vacumn again, after lunch it's working fine.  I rebuilt the pump 5-6 years ago and replaced the lines from the pump to along the fire wall last summer due to crumbling connections.   What could be causing a random loss of vacumn like this?  I already ordered a posi-lok cable system for the axle as I don't want to be caught with my pants down in the snow.  

Personally I would get some air brake line and re-run all the vacuum lines on the truck then using small pieces of rubber to hook up to the barbs. I've been looking at customer trucks and my own trucks and realize that the vacuum setup could be better. A matter of fact the entire driver side of the engine could be cleaned up of wires and vacuum line. Mostly the plastic lines get brittle and start to leak the only way to fine the leaks is to bow the plastic lines till the crack is noticed.  

Is there a lot of lines behind the dash?  I plan on replacing the dash core this year so I may be able to clean/replace some of that mess.  

Not really. There's the bundle from the HVAC controller. That goes into a quick connect for heater box removal, then its just the inputs for the vacuum motors. I think its 5-6 lines plus the "feed" line?

 

If one has a manual trans and no CAD, the only vacuum operated stuff is the hvac box. I've thought about using the 3rd gen vacuum pump (its electric), and removing the gear driven vacuum pump. There are kits that put a gear and flange on the PS pump. I think its a 4bt kit actually.. 

12 hours ago, Silverwolf2691 said:

Not really. There's the bundle from the HVAC controller. That goes into a quick connect for heater box removal, then its just the inputs for the vacuum motors. I think its 5-6 lines plus the "feed" line?

 

If one has a manual trans and no CAD, the only vacuum operated stuff is the hvac box. I've thought about using the 3rd gen vacuum pump (its electric), and removing the gear driven vacuum pump. There are kits that put a gear and flange on the PS pump. I think its a 4bt kit actually.. 

 

I was going through a parts catalog on the crapper the other day and saw the electric 3rd gen vac pump and wondered if such a conversion were possible.  I do have a spare 2nd gen vac pump waiting for a rebuild but I still hate swapping them out.  

Still can't remove the 2nd gen vacuum pump because you need it for the power steering pump mount. 3rd gen has belt driven pump.

You can. Power driven diesel sells a billet and chrome one but its like 4-500 bucks or something like that..

Ok. Bit too expensive just to delete vacuum pump. Wow.

Might need that number to go up.. Just relooked around.. The cast version from a 4bt powered "bread van" is ~$400. The billet aluminum and chrome one is probably a lot more..

Maybe just leave the dead vac pump in there and run the electric on the side.  The 3rd gen pump is only $100 from LMC.   

Still end up doing seal kits off and on to keep the oil leak at bay. If your going electric vacuum pump you should consider the full delete. 

Electric vacuum pumps and direct drive PS pumps? I did not know this kind of sorcery existed! What a brilliant idea, not so easy on the pocket book, but definitely a route to consider next time since I already built vacuum pump and got a new PS pump...

 

Electric vacuum pumps. Kind of like the argument of electric fuel pumps vs mechanical fuel pumps. Yeah I can see this being a different answer but still in all yes electric motors have wear limitations. Electric vacuum pumps will still put the same kind of load on the engine being the load is on the alternator. I will admit the old mechanical vacuum pumps are way more simpler, easy to rebuild, and the seal kits are fairly cheap.

Right now the only attraction of the electric pump would be ease of replacement.

All these vacuum pump problems really make me appreciate my older vehicles more. The "choke cable" operated blend doors, etc. just never seem to give sudden problems. No vacuum gizmos for the axle.

On 1/19/2022 at 6:20 PM, LorenS said:

All these vacuum pump problems really make me appreciate my older vehicles more. The "choke cable" operated blend doors, etc. just never seem to give sudden problems. No vacuum gizmos for the axle.

 

I'll agree... The whole problem stems from the fact that all 1st Gens, 2nd Gens, and part of the 3rd Gens. The gasoline side was using vacuum for all the stuff like HVAC controls and axles (4wd) and the cruise control. Diesel don't have any way to create a vacuum strong enough. So vacuum pump were added. Once we go to the 04.5 roughly IIRC is the start of all non-vacuum control trucks. Now when you trade for electric HVAC that get expensive. Dash controls for HVAC is not cheap. Then being most of the truck is CANBus messages for control makes it tougher to work on as well. So if there is a bad wire or voltage of the message is skewed then you might be really pissed of where turning on the wipers will turn the hi beams on. Yes I've seen this before and it super tough to fix. 

20 minutes ago, Mopar1973Man said:

turning on the wipers will turn the hi beams on

I think I could handle the other way around, but depending on where one lives, this could get a guy in trouble.  An old friend of mine had a Mustang that whenever you turned left, the horn would honk.  He also happened to live in a rough part of town - it was not a good combination!  We soon found the chaffed wire and he could once again turn left without worrying about flying lead.

I think you have another vacuum line leak - maybe from the firewall area down to the t-case, or under the hood again. It sounds like when it's cold the break is evident, but when things warm up, it could seal itself up somewhat. 

Plastic tubing for the vacuum lines is well rather brittle at this stage of life on any truck. It would be a good idea to replace all that plastic tubing along the cowl and down to all the device with air brake tubing. This stuff is pretty tough and works for vacuum just as well. Just need some rubber vacuum hose to fit over the air brake tubing to hook back up to nipples on devices.