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What did you do with your GMT400 today...or yesterday....

You mentioned that your boost gauge is actually measuring exhaust gas pressure? it took me a bit to think about it, but if there is a leak in the tiny tube up near the gauge, how exhaust gasses could make it's way into the gauge it's self causing the coiled copper tube inside the gauge to distort. this may be why it's not reading right
 
dbrannon79 said:
You mentioned that your boost gauge is actually measuring exhaust gas pressure? it took me a bit to think about it, but if there is a leak in the tiny tube up near the gauge, how exhaust gasses could make it's way into the gauge it's self causing the coiled copper tube inside the gauge to distort. this may be why it's not reading right
Click to expand...
Yup.
Looking it over and IDK whats going on with that.
I need to remove the floor from that pod and see if there is any problems within the pod.
I do have six foot of (IIRC) 1/4” copper tube from thd exhaust manifold to the pipe to ferrel fitting adapter. The plastic tube shows absolutely no sign of failure. After a nice drive the copper tube at the end feels plumb cool. No kinks or sharp bends to hold in the pressure.
After setting for the night, that gauge is still at the same pressure.
I’ll try switching tubes and see how the green needle does on that side.
 
LP pressure
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Post FFM pressure, right at the IP.
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Not sure what I need to do to make this gauge more visible on the numbers and needle.
I need to pry off that silver bezel then suppose to be able to change gauge face colors.
 
MrMarty51 said:
Yup.
Looking it over and IDK whats going on with that.
I need to remove the floor from that pod and see if there is any problems within the pod.
I do have six foot of (IIRC) 1/4” copper tube from thd exhaust manifold to the pipe to ferrel fitting adapter. The plastic tube shows absolutely no sign of failure. After a nice drive the copper tube at the end feels plumb cool. No kinks or sharp bends to hold in the pressure.
After setting for the night, that gauge is still at the same pressure.
I’ll try switching tubes and see how the green needle does on that side.
Click to expand...
you can leak test it by connecting an air regulated air supply to the line at the manifold end with a shut off valve. fill with 15-20 psi air pressure and let it sit for a bit.

does the plastic tube at the gauge end use furls but nothing inside the tube to prevent it from crushing shut? I have had that issue in the past. tightened the compression fitting too much and it closed off the tube. it might not have been completely crushed shut when you installed it, but now with the heat of the sun beating into the cab the tubing has gotten soft sealing it up trapping pressure in the gauge.
 
if you want to hide all the wires and tubing, get one of those carpeted dash covers and run the wires and tubing under it. take some scissors and snip an opening for them to come out at the gauge or let them come out from the defrost vent opening. use some Velcro to affix the pod to the carpet dash cover so it will stay in place. no need to trim or cut into the dash!

second idea is a pillar gauge pod. I think I saw one that I might could print with my 3d printer! those things sell for $50 or so. printing one is way cheaper!! lol
 
dbrannon79 said:
I found this one online. I might attempt to print one just to see how it looks! it's configurable and stackable so you can use as many as your want.


View attachment 95377
Click to expand...
I like that.
If all the gauges was the size of the smallest one, if thats a 2-1/16th then it looks like there would be room for the three I now have in the pillar pod, plus, the three thats in the three pod atop of the dash unit.
Get one printed up with six 2-1/16th gauge holes, to fit the pillar of the GMT400s and I’ll get some cash fired right offt to You.
 
@MrMarty51 I'm running a draft test print now, and will test fit on my 95 tomorrow. Just using some PLA filament for the test run, it's not suitable for use in a vehicle unless it's heat treated otherwise it will distort and melt in the heat. I can use it to make sure the fitment is right and make any changes as needed. Then later I can use ABS or PETG plastic for a final print as both will hold up well in the heat!

Most likely the final result will need to be painted to color match the interior. I personally would sand, use high build primer and paint to match so it would look as if it's part of the truck!

the 3d model looks as though it's intended to use screws to affix it to the pillar, I think it should be light enough even with the gauge to run two strips of 3M self adhesive Velcro to stick it so it's serviceable and not have to make any screw holes in the plastic pillar cover!

IMG_0563.jpg
 
My son and I put together a small print farm in the spare bedroom over the last few months. The work area is a bit of a mess right now with my most recent (used) printer being overhauled (far right in photo), but this is what has been keeping me occupied and off the forum for a bit. I had invested into three used printers, rebuilt them from the ground up and my son invested into a new expensive multi-color printer (far left in photo)

after seeing a few folks in our area put up booths at the city's local trade days where folks sell and trade items for side cash, we both wanted to try having a go at it!

IMG_0564.jpg
 
The pillar pod now in My truck has three screws affixing it to the piller and it looks mighty phine.
My interior is grey so if there is some grey printing material let me know and I’ll have an order shipped in to You.
 
Well spent the day playing in my cad software on my pc along with doing other household duties in between.. made several iterations of this stack-able gauge pod and now I think we have a winner! I did a custom base to try and fill in as much of the gaps on the pillar as possible while still keeping it tunable for gauge sizes on the fly. I still have to test fit my boost gauge in the hole, but measuring, it should work fine. Need to order some ABS filament to color match and hold up to the heat in the cab, I will do that later in the week.

here are the results...

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Took ‘99 K2500 Suburban in for ac recharge. Last charge a year ago. Mechanic says the compressor has a really slow leak and only fix is to replace it. Need to go through receipts to check on the warranty for the Sanden compressor as it was installed just two years ago.

Separately also got my forged LCAs back after getting ES polyurethane bushings and Moog ball joints pressed in. Ironically he had another set of GMT 800 forged LCAs from a Duramax getting the same work done.

IMG_9864.jpeg
 
Well this evening I started tearing into the 95 to attempt replacing the ac condenser. started with the brush guard, I figured out that I can remove the 4 bolts on the bumper and let it hang since the lower part is bolted to the frame. that gave me enough room to get the grille out. pulled the inner fender on the passenger side to get at the liquid line. pulled the line and the condenser out. got the new line in and the replacement condenser in place. There is quite a large gap on the right side of the condenser for air to go around as well as a smaller gap up top and on the left by the factory PS cooler.

I need to figure out something to block that area off so air is forced to go through the condenser. also found a pickup bed full of leaves behind the old condenser that I had to clean out. it hasn't been that long since I cleaned all this out! how does all this much compost materials make it way in there!! the old condenser I had put some foam and plastic covering the openings!

anyway I got it together enough to pull a vacuum to leave it overnight. Here are some pics...

Notice the repair on the old condenser someone did before I bought the truck and the welded liquid line with a different fitting!

IMG_0583.jpg
IMG_0584.jpg
IMG_0587.jpg
 
Here is the install...

the condenser is a used one I pulled from the pick a part yard last year. had it in the garage all this time only because of the welded line wouldn't fit the threads on the condenser.

what do y'all think I should use to fill the open gaps up top and mainly on the right side where the fittings are? to me that would cause air to bypass around the condenser. back when I had the radiator out I had used some pipe insulation to fill the gaps between the radiator and the support and shroud. that worked well and has held up good.

IMG_0588.jpg
IMG_0589.jpg
 
I ended up re-using a piece of plastic I had originally cut from an old ice cream bucket, reshaping it to fit to cover the open gap on the right side.

recharged it using the R152a I had recovered from the system before I started and had to add a little more from a can I had, about 18 oz in total charge. using this refrigerant you have to calculate about 10-15% less than the factory 134a charge so it's close but needs slightly more.

ran the ac and had about 43 degrees at the vents with the fan on max and the PTO switch on running at about 1k rpm. pressures started off at 22 low 250 high and very slowly climbed up to 25 low and 300 high until my electro-fan clutch kicked in, then pressures went to around 150-200 high and below 20 low which caused the compressor to start cycling rapidly. it needs a little more charge.

I also need to do the retro-fit on the cycle switch so I can install an adjustable switch. I did this on the 93 using the same refrigerant setting the cycle switch to be off at 15 psi which it cools great, but its a pre 134a system. the 93 had 134a from factory but that was the first year they introduced it being they just built an r12 system and slapped a 134a sticker! The 95 is just 2 years newer.

Shut it down for now till I can go pickup another can of office duster (r152a) and the new cycle switch.

Oh BTW if anyone needs the info, on the newer 95+ rigs if you need an adjustable cycle switch, a cycle switch from a 95-97 ford F-150 will thread onto the accumulator. our accumulators use a metric thread where the older rigs like my 93 use standard 1/4" male flare like the old r12 systems.

I recommend using your air compressor and a pressure regulator to set the adjustment prior to installing. it's hard to adjust on the vehicle, just use a rubber hose and clamp over the outer part of the switch, you only want it to turn off at 15 psi. it will turn on at around 25-30 psi. factory setting are off at 21, on at 44. use this same concept for converting ac systems to run enviro-safe (propane-butane mix)
 
R152a is much safer than any of the flammable refrigerants and the molecules are larger than r12 or 134a. hence why you use less, also leaks slower if there is a leak. lower pressures and less drag on the compressor too!

I'm running the GM orange orifice tube which is 0.062 vs the factory black one that is 0.072.

I will let the system rest for now and try it again later today to see if the pressures spike up over 350 as soon as you turn it on like it was doing with the old condenser and modified repair the PO did. hoping that is fixed.
 
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