Bang for the buck Functional Renewal of rust belt '99 C2500

[Road Trip]

Greetings fellow GMT400 enthusiasts,

Just about a year ago I heard through the motorhead grapevine that
an unusually clean (for upstate NY) older Chevy pickup was being
offered for sale.

I didn't get my hopes up, because it seemed that other people's
definition of 'clean' didn't seem to jibe with my own...by a long
shot! FWIW, my personal Prime Directive for buying my next
ride can be simply stated in 2 simple rules:

1) Don't care about the miles or the current state of the
mechanicals, but it has to be rust free.

2) it has to have a manual transmission!

Rust is bad juju. While I've been fortunate in buying
a series of low-cost vehicles that have given me more than they
have gotten...I eventually lost every single one of them
to rust. Not the outer surface cosmetic issues, but
the no-kidding showstopper stuff. (ie: the unibody where
the lower control arm is supposed to connect to is MIA.)

Of course, getting rid of a car that broke your piggy
bank and gave you nothing in return is always pure
joy to jettison. But when you lose a faithful
traveling companion that would run for you even
when it shouldn't have...that is the very definition of
sadness. (No doubt anyone reading this in an old
truck forum is picking up what I'm putting down. :0)

...but I digress. If you go here you can see a brief
description of the '99 C2500 drivetrain in my
Introduction thread.

But when I saw the truck in person, the truck just exuded
a quiet, heavy duty minimalism...the zen of a proper
work truck. (!) When the big block fired right up and
rumbled like Niagara Falls, I knew that this was going to
follow me home. :0)

Like my favorite aircraft (F-106 & SR-71) the GMT400
series has the same kind of classic 'form follows function'
styling that never gets old -- I actually prefer this less
busy look to today's offerings?

Finally -- enough of the setup. First, here's the truck after
a good cleaning / wet-sanding / machine polishing using
the Meguiar's Mirror Glaze product line:

You must be registered for see images attach

But in order to truly appreciate what a (relatively) rust-free unicorn
that this truck is here in Salt City, take a look at three other trucks
still on the road that I picked at random, all within 5 minutes of where
I'm typing this in:

Mechanic's daily driver at my favorite tire store. (Note: Photo taken late November '22 -- a frosty commute)

You must be registered for see images attach

Local Plow Truck:

You must be registered for see images attach

(Neighbor's newer lashed-up pickup)

You must be registered for see images attach

The Moral of the Story? Anything > 10 years old in Syracuse
is rarely seen. And almost always, if seen they aren't clean.

So...if my following posts seem to show successful old truck
ownership as an unrelenting focus on stopping rust before it turns steel to dust...
remember that I have no fear of mechanical issues, but at the same time these photos
definitely keep me up at night. :0)

Who'da thunk? Neil Young was right...

 

[HotWheelsBurban]

Greetings fellow GMT400 enthusiasts,

Just about a year ago I heard through the motorhead grapevine that
an unusually clean (for upstate NY) older Chevy pickup was being
offered for sale.

I didn't get my hopes up, because it seemed that other people's
definition of 'clean' didn't seem to jibe with my own...by a long
shot! FWIW, my personal Prime Directive for buying my next
ride can be simply stated in 2 simple rules:

1) Don't care about the miles or the current state of the
mechanicals, but it has to be rust free.

2) it has to have a manual transmission!

Rust is bad juju. While I've been fortunate in buying
a series of low-cost vehicles that have given me more than they
have gotten...I eventually lost every single one of them
to rust. Not the outer surface cosmetic issues, but
the no-kidding showstopper stuff. (ie: the unibody where
the lower control arm is supposed to connect to is MIA.)

Of course, getting rid of a car that broke your piggy
bank and gave you nothing in return is always pure
joy to jettison. But when you lose a faithful
traveling companion that would run for you even
when it shouldn't have...that is the very definition of
sadness. (No doubt anyone reading this in an old
truck forum is picking up what I'm putting down. :0)

...but I digress. If you go here you can see a brief
description of the '99 C2500 drivetrain in my
Introduction thread.

But when I saw the truck in person, the truck just exuded
a quiet, heavy duty minimalism...the zen of a proper
work truck. (!) When the big block fired right up and
rumbled like Niagra Falls, I knew that this was going to
follow me home. :0)

Like my favorite aircraft (F-106 & SR-71) the GMT400
series has the same kind of classic 'form follows function'
styling that never gets old -- I actually prefer this less
busy look to today's offerings?

Finally -- enough of the setup. First, here's the truck after
a good cleaning / wet-sanding / machine polishing using
the Meguiar's Mirror Glaze product line:

You must be registered for see images attach

But in order to truly appreciate what a (relatively) rust-free unicorn
that this truck is here in Salt City, take a look at three other trucks
still on the road that I picked at random, all within 5 minutes of my
driveway:

Mechanic's daily driver at my favorite tire store. (Note: Photo taken late November '22 -- a frosty commute)

You must be registered for see images attach

Local Plow Truck:

You must be registered for see images attach

(Neighbor's newer lashed-up pickup)

You must be registered for see images attach

The Moral of the Story? Anything > 10 years old in Syracuse
is rarely seen. And almost always, if seen they aren't clean.

So...if my following posts seem to show successful old truck
ownership as an unrelenting focus on stopping rust before it turns steel to dust...
remember that I have no fear of mechanical issues, these photos definitely keep
me up at night. :0)

Who knew? Neil Young was right...

Wow I had heard the 800 series trucks were bad about rusting...
And amazing that the Ram, in a generation known for rusting, is in better shape than the two newer GM's.

Definitely New Yuck.....

 

[HotWheelsBurban]

That is a beautiful truck, obviously well cared for. I too appreciate the clean lines of the 400 series. And the body color matched wheels look great(just need trim rings and those are stainless steel). My Burbs have come with aluminum wheels but my crew cab long bed came with steelies. Eventually getting painted Rawhide Metallic to match the body, or the aluminum 8 lug wheels the 800s used.
Picture is my truck at one of my favorite wrecking yards.....

 

[Road Trip]

You have a good eye for detail!

Thanks for the positive feedback on the body color matched wheels --
I always liked that look on vintage restored pickups, so I decided to
give it a try.

As a matter of fact, when I bought the truck the original silver steelies
had been resprayed rattle-can black...and of course both paint films had failed.

Here's an 'as-purchased' photo of what I started with:

You must be registered for see images attach

For me, in the 'as purchased' condition the ugly wheels actually
drew the eye away from the truck itself. And since here in the
'hood it's very popular to put zany shiny aftermarket wheels
on a rusted out hooptie...well, as someone who enjoys
driving differently in a low-key way, this was definitely
income that I didn't want to dispose of in that way. :0)

Clean factory aluminum wheels would have been nice, but
acquiring a remanufactured set of those would have blown
the austere budget I have to work with. :0)

In the near future I'll post a series of photos showing how
I was able to refinish the steelies in such a way that they
all but disappeared from view, but at the same time add to
the overall look/feel of the beast in an understated
way.

 

[HotWheelsBurban]

You have a good eye for detail!

Thanks for the positive feedback on the body color matched wheels --
I always liked that look on vintage restored pickups, so I decided to
give it a try.

As a matter of fact, when I bought the truck the original silver steelies
had been sprayed rattle-can black...and of course both paint films had failed.
Here's an 'as-purchased' photo of what I started with:

You must be registered for see images attach

For me, in the 'as purchased' condition the ugly wheels drew the
eye away from the truck itself. And since here in the 'hood it's very
popular to put zany shiny aftermarket wheels on a rusted out
hooptie, so that was out of the question.

Clean factory aluminum wheels would have been nice, but
acquiring a remanufactured set of those would have blown
the austere budget I have to work with. :0)

In the near future I'll post a series of photos showing how
I refinished the steelies in such a way that they all but
disappeared from view, but at the same time added to
the overall look/feel of the beast.

Yup I hear you on the zany aftermarket wheels! People in Houston seem to think that putting big ugly but shiny chrome rims and rubber band tires on their vehicles makes them hot rods or customs. No thanks folks, I go to proper custom car shows and know what's what!
I used Brasso liquid on my center caps and that shined them up a little. I need to take them off and properly polish them, but just haven't gotten around to it. I see sets of the wheels I want , on trucks in the yards....when I'm broke! There was actually a set on a truck Saturday morning at the yard closest to me, that looked good, but I didn't have the $300 it would take to bring them home. I haven't been working for several months so the truck budget is pretty small right now.... I was literally counting out $1 bills to get the Escalade parts and 88-89 quad beams that I got!

 

[Road Trip]

Rough Idle / Hesitation / Check Engine Light -- Troubleshooting multiple overlapping issues, one layer at a time

Alright, for strict continuity I could continue to describe how I took the old steelies
and ran them through my blast cabinet & de-emphasized them by painting
them to match...let's save those photos for another day.

Instead, I'd like to share some basic engine troubleshooting tips & hints, using
the debug of the 220K mile L29/Vortec 7400/Gen VI 454 powerplant that
followed me home as a case study. (NOTE: Obviously the veteran mechanics
that populate this website are not the target audience of the following, so no
offense intended.)

****

Alright, before I share what I found, I'd like to outline the very basics of
analytic troubleshooting. It may seem like stating the obvious, but in the
heat of the moment these laws of troubleshooting are your friend, whether
you are troubleshooting with a pico scope + pressure tranducer(s), a pro scanner
with live data, a simple code reader...or even old school mano a mano...with no
provisions but an open face. :0)

Troubleshooting Laws

1) Worst first -- the Intermittent. If you can't figure out how to fix it...then it's
time to figure out how to break it. Stated another way, you can't fix an
intermittent until you can first figure out how to break it at will. Once you
figure out how to stimulate a fault at will, then if you share those steps with a
SME (Subject Matter Expert) they will be able to A) give you additional troubleshooting
checks to further tighten the problem statement, or, B) tell you which component is
the root cause. (Note: Once a mentor shared this with me, I found that my
troubleshooting was at least an order of magnitude more fruitful. (!)


2) The tighter the definition, the cheaper the fix. If you go to a mechanic and
tell him "the engine sux", either he will ask you a series of diagnostic questions
in order to tighten up the problem statement (good)...or he will take you at your
word & sell you a new long block crate motor. (intellectually lazy but profitable)

Instead, for the same scenario your problem description is "The engine oil pressure
at idle was fine right up to the point where I did an oil change", then the mechanic should
be able to diagnose a cost-effective fix in a handful of follow-on queries.

3) The older the machine and/or the more previous owners it has had,
the higher the probability that there could be nested failures. Few things can shake
your troubleshooting confidence as when you have a problem, you replace a failed
part that causes this kind of problem...and yet the vehicle is still exhibiting
the same exact symptom as before. You did correct 'a' problem, but a
2nd overlapping problem has obscured the fix. :-(
This scenario isn't fair, but it does happen.

As a matter of fact, in the next reply to this thread I'll walk you through how,
in order to get the newly acquired big block to idle properly, I had to fix the idle, retest, fix
again, retest, etc. -- for a total of 4 iterations!

Hope others will find the following useful. Old trucks can run like Day 1 -- why not
drive something that runs like a new truck for $$,$$$ less money?

 

[Road Trip]

Rough Idle troubleshooting, 1st Pass

When I went to see this truck, I was hoping that the engine was stone
cold instead of already warmed up. (Starting an unknown engine from
stone cold reveals a lot about the mechanical state of affairs.)

I opened the hood & touched the exhaust manifold with the back of
my hand. Stone cold - yes! Turning the key, the engine started
almost immediately, with zero piston slap, or rod knock until the
oil pressure comes up. The lifters didn't require pumping up, and
the rest of the valvetrain was dead silent. So many expensive
sounds NOT present on 1st impression! All the accessories
were quiet as well. (alternator, PS pump, water pump, A/C clutch)

No signs of any new gaskets...the engine appears to have been
never opened up.

That's the good news. The bad news? There's a check engine
light, and although the engine is mechanically quiet, the idle
quality seemed weak and randomly rough. Not a steady dead
cylinder chug chug chug, but misfires on most/all cylinders?

Encouraged by lack of expensive noises during the cold start,
I decided to take a gamble on the rough running aspect &
purchased the truck. Driving the truck on the road, it
hesitated on acceleration, felt lethargic, & just had that
"always driving uphill" feeling, even on level roads.

Funny thing, during heavy throttle the truck seemed to be able
to pull it all together & feel more like the big block it was supposed to be?

The 1st step was to check the spark plugs & replace them if there was any question about their serviceability:

You must be registered for see images attach

They obviously had a lot of miles on them, the gaps looked excessive,
there were oily threads on the #3 plug, and the #6 plug had the
most deposits of the bunch?


Previous mechanic a little loose and fast with the gapper tool & twisted the ground electrode off-center in the process?

You must be registered for see images attach

Old plug on left shows asymmetric electrode wear from twisted ground strap. Nice, sharp discharge surface on new plug.

You must be registered for see images attach

Rounded edges require mucho KV (KiloVolts) before the spark will jump the gap. Plug on right will require much less KV
to jump the gap, placing less stress on *all* of the related ancillary bits. (Spark plug rotor, cap, wires, etc)
Please keep this in the back of your mind for later...

Original plug gap specs were .060" -- GM later revising gaps to .045" per service bulletin. Old plugs set to old spec. New plugs = ?

You must be registered for see images attach

NOTE: All 8 new plugs were gapped to .045" before copper antisieze was applied and torqued to spec.
Also, dielectric grease applied to inside of spark plug boots prior to reconnection.

RESULTS?

Major improvement to idle quality. Hesitation all but eliminated. Big improvement for $24!
(8 Bosch 6706 @$2.99/each -- Autozone clearance)

Can it be that the idle was fixed this easily?

 

[Road Trip]

Rough idle troubleshooting -- from steady good to intermittently good, phooey -- (2nd Pass)

For all of maybe 48 hours the Check Engine Light went out & stayed out.
The idle was much improved, not bad at all for the age & miles on the odo.
I was driving around with a sheet-eating grin.

But right about the time that I had finished counting my troubleshooting
chickens, the Check Engine Light comes back on, accompanied by what
felt like a single dead cylinder -- a rhythmic chug chug chug. WTF?

And then, just as suddenly it would disappear. And come back. Rinse
& repeat. My first thought was to grab a code reader & see what the
computer thought. But the previous owner had mounted the trailer
brake controller in such a way that the OBD2 port was physically
blocked?

Phooey. I'll just give the engine bay a good visual, and if no joy,
then I'll make the OBD2 port accessible & press.

Driver's side spark plug wires routed correctly, in free air, no grounding/signs of arcing

You must be registered for see images attach

Meanwhile, on the Passenger side the #6 spark plug wire was routed so that it was lying on top of a spark plug heat shield & showing signs of arcing to ground

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Backed away camera in order to give a big picture perspective on the #6 spark plug wiring error

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Note: Sharp-eyed GMT400 enthusiasts will see an Easter Egg in this photo of another (unrelated) issue to be discussed in a future posting.


If you go back & look at the photo of all 8 plugs after removal, #6 was the dirtiest of the bunch. Here is some carbon buildup from the shorting spark plug wire.

You must be registered for see images attach

Re-routing the #6 spark plug wire now gave ~1" of clearance in all directions in boot area. This plus a new plug gapped at .045" did the trick!

You must be registered for see images attach

Now the engine was hitting on all 8, the idle was smooth, and best of all,
the Check Engine Light extinguished...and stayed out. Hmmm, it only
took 2 passes to fix the idle?

 

[Road Trip]

Unpredictable, random idle roughness...now with no check engine light! -- (3rd Pass)

Now that the Check Engine light was out & staying out,
the feeling was that this truck could be trusted in an ever
widening circle around home base.

To recap, the 1st pass made the Check Engine light go
from constantly on to Intermittently On.

The 2nd pass repair made the Check Engine light
go from Intermittently On to always Off.

Sounds like solid progress. And it was for the most
part. For example, no check engine light = you don't
have to worry if the cats are being overheated/poisoned.

...But for me something that just grates on the nerves is
a rough running engine that at the same time never sets
the Check Engine light?

Heck, if the stupid thing was carbureted I could
explain it away that A) the Baro changed, B) got a little
bit of water in the fuel from that not-too-busy station
with the old tanks, C) the heat stove air valve might
be malfunctioning, or D) one of the dozen different
vacuum lines split, E) there's too much heat in the
intake manifold crossover passage, F) I got carried
away & shouldn't have blocked off the heat riser
passages like the Let's Go Faster article said was just
the thing to do, G) some dirt must have gotten
past the spring-loaded inlet fuel filter, H) maybe this
is 'cuz of the newfangled oxygenated fuel, etc, etc.

Kinda like listening to LP records (aka 'vinyl') ...you
just got used to the pops & ticks imperfections as
part & parcel of the presentation.

On the other hand, the EFI cars are supposed to
be perfect. Like when CDs came out, and were
marketed with the expectation that you would
enjoy "Perfect Sound Forever".

Just kidding. In my world, if I can feel the
engine is off it's feed, I prefer the computer
to let me know that I'm not hallucinating
by setting the light. Having to spelunk
around in the Mode $06 data in order
to check out stuff that has yet to cross
a reporting threshold feels like playing
troubleshooting peek-a-boo.

But I've had my friends patiently explain to me that
most folks are not like me, and the manufacturers don't
want the reputation of being the brand that constantly
sets the Check Engine light. So, there are error-reporting
thresholds that have to be met before the light is illuminated.

Also, There are all kinds of counter-intuitive
strategies that are employed to keep the
cat(s) from melting down. And so on & so forth.
(end of rant. :0)

...but I digress. Now, instead of
new truck perfection -- you know, where you
have to look at the tach to see if the engine
is still turning over...I now had an engine
that smooth, but at seemingly random
intervals the engine would shake the
cab just enough to let me know that
something wasn't right...some of the
time.

As I used to teach in a previous life,
"The closer you get something to right,
but it isn't *completely* right...then the longer
you will have to wait for the Intermittent
Problem to resurface. Which is both good
and bad. Good in that the vehicle is
running right 98+% of the time. Bad, as the
mechanic owning the problem you are
always waiting for the other shoe to drop!

So I needed to stimulate the fault, but how?

The answer presented itself during a midwinter
oil change. I accidentally discovered that by
removing the Oil Filler Cap while the engine
was running that I adversely affected the
idle quality?

Playing around with the cap, I found that IF I left the cap
off for a bit then the engine seemed to smooth
back out. IF I put the cap back on, after a short period
of time the engine would again smooth out. So,
steady state was fine, but sudden changes seemed
to upset the idle stability? (NOTE: Since the PCV
valve air into the intake isn't measured by the MAF, you
would have the situation where the MAF reading is steady state,
but at the same time the MAP sensor is seeing a disruption
from changes in this 'false air' coming in?

NOTE: The above is pure conjecture on my part. I'm still
trying to figure out which diagnostic tools I'm going
to purchase invest in. (I still remember what it felt
like to use that old Sun 1115 day in & day out --
just the cylinder deactivation feature alone saved countless
troubleshooting hours in a given week.)

Maybe somebody has already done a data capture on
this very issue? I know that when I was troubleshooting
this, I looked a lot, but try as I might I couldn't find
anybody discussing this possibility?

The good news is that I could now stimulate the fault &
break it at will. How? After 23 years of thermal cycling,
mixed in w/road vibrations & wind buffeting from the
monster 9-bladed HD cooling fan, the fill cap was a
sloppy fit. Just grabbing it & wiggling it would disturb
the idle. It just seemed janky, not fitting in with
standard big block design?


The Vortec 7400 Oil Filler Cap, right in the center front of the engine bay

You must be registered for see images attach

Here's the exact replacement part that I ordered:

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Here is what I found. A side by side comparison shows the root cause was a worn o-ring on the original cap. The new cap fit TIGHT...as you expect!

You must be registered for see images attach

With the new cap secured onto the top of the fill pipe, attempting to wiggle it produced zero movement.
More importantly, the idle quality didn't seem to change at all.

I was completely chuffed.

I was thinking to myself...well, it only took 3 iterations in order to really fix this idle...but
a smooth-running big block is nothing if not empowering. :0)

 

[454cid]

I still have my original oil filler cap. I just clean it up and install a new o-ring when it gets loose.