1972 GMC 2500 6.2 Diesel

[dagnabbitt]

I have my new drums and shoes installed, they really are big beautiful hunks of metal. Side by side it is also apparent how much material was missing from the old ones. Once installed there was much bleeding of brakes, I do not think that there was much fluid in the system at all.

My local parts supplier was unable to find me parking brake cables, so I posted for help on the forum and received some links. I have ordered a couple and hopefully they are the correct ones. There are numerous types available based upon whether or not the truck is a V8, has leaf or coil, is a Longhorn or not, and curiously, if the trans is a TH400 or some other. The old cables are 41 inches long and have a bracket that bolts to the back, hopefully I have the right ones on order.

[dagnabbitt]

With the help of the forum I managed to find the right parking cables for me. Of course, I tend to forget that not everyone is the fusspot that I am. I agonized over whether I needed the 39" or the 41" cables, and then noticed that the last guy just welded a couple of cables together to form the intermediary line. Oh well. You know, it isn't going anywhere, it was actually a pretty good repair.

The brake saga is not over: I have replaced the hydroboost. The old one was not doing its job. Furthermore when trying to bleed the brakes and failing, I discovered that the master cylinder is likely shot, too. I think it was the OEM one, made for a gas with vacuum assist: I might be talking out of my hat, but I think that the hydraulic pressure of the hydroboost is about double what you get from a vacuum, which means that it might not have held up in this application, ie it might have blown the master cylinder. Anyway, I have a 3/4 ton diesel master brake cylinder arriving tomorrow.

I always say I don't mind spending money on brakes, tires, and batteries, but this truck is testing that theory. It will stop on a dime, though.

[dagnabbitt]

New hydroboost and new master cylinder. Just need to bleed the brakes and I can give it a spin.

[dagnabbitt]

The brakes seem to be functioning like they should: the effect of hydroboost on a brake pedal is kind of unique and the driving experience is a bit different. My last diesel was a Ram 3500 and I never paid attention to the brakes. It was a modern vehicle and it worked perfectly so I paid no attention to it. It was useful but boring and I barely remember it. What I am saying is I think my new brakes are good but do not have a reference point to compare to.

To be clear, prior to doing this work I said I thought the truck "stops like a somewhat modern truck": I would later learn that the rears did not work at all, the master cylinder was shot, the hydroboost was garbage, the parking brakes were seized. The only thing keeping me from piling into a bread truck was that the front brake shoes had some particularly pointy rivets. I am a lousy measurement of whether brakes work, I guess. I live in the moment, and at the moment I am alive. I assume the brakes are better than they were before.

Anyway since I have some shop time with my mechanic friend, we are skipping the test drive (see above, who cares) and going right into fixing the steering. Earlier I mentioned that this thing turns well one way, but not so much the other way. So the first thing to try is just removing the pitman arm and centering the wheel.

Since I am pretty sure I am done with the brakes I felt confident enough to finally add my hubcovers. I am pretty pleased, they suit the truck and just disappear into those satin powdercoated rims. The fronts are repops, but the rears are original circa 1991 dually covers. They are not common as decent survivor parts... these four caps came from ebay and four different corners of the US.

[dagnabbitt]

I've been putting some miles on the truck, and really enjoying it. It has an amazingly nice ride - especially for a leaf spring truck - which I attribute mostly to the tall Firestones I put on. I certainly do not recall it being this nice with the 22s.

I also think that with the diesel engine, which is heavier than a big block (I think) that the suspension is working to its optimal... uh, level. I dunno how to explain it, except that when I had a 1 ton it was hell to drive unless it was loaded: with a trailer it felt like a Cadillac... maybe it is something like that.

In addition to the brake work my steering is fixed, my friend fiddled with it and it is straight now. There is a pesky oil leak somewhere on the right side of the engine, but I am not in much of a hurry to find it.

Although I've gotten compliments on the interior I am thinking of changing it to black: my 67 K20 came with a bunch of 72 parts including a set of door panels and armrests, among other things. I have an idea for seats etc that I would like to try, too.

[yuccales]

I like that truck!

[dagnabbitt]

Originally Posted by yuccales

I like that truck!

Thanks! It's really growing on me. Now that it has new brakes I like it much more.

[dagnabbitt]

I think I easily put 400 miles on a tank this week, driving it to work and out on errands. Today I went out in the country all afternoon on a long drive and went down some gravel: there are some people on this board who aren't scared of anything, except maybe driving their rides on gravel. I'm not scared of anything but having to paint this thing.

The truck is so comfortable to drive. It feels like an old half ton, or a modern 3/4 ton if that makes sense. I have a 2010 Yukon XL 2500 that rides the same anyway. You can steer with it one finger and the brakes are very responsive.

The speedometer is interesting in that it reads in mph exactly half what it is doing in kph: all the time. That is, when I it says I am doing 50mph, I am doing 100kph. When it says I am doing 27mph, I am doing 54kph. It is exact, I have checked it with GPS. I think it is the most fuel efficient vehicle I own for sure.

Pics are of the engine during an infrequent fill.

[skinnan]

Love the write up...I have a very similar truck. Been looking for wheels for it. Did you say you got these wheels from a Ford E250? Any idea what year works?

[dagnabbitt]

Originally Posted by skinnan

Love the write up...I have a very similar truck. Been looking for wheels for it. Did you say you got these wheels from a Ford E250? Any idea what year works?

Nearly any year up until around 2010, I think, which is when things started going metric. They are pretty common, just make note of whether or not you want one with hubcap nubs or not.

[dagnabbitt]

It has been awhile: the diesel does not like winter much, so I have not been driving it. But when the block heater is plugged in it will start up fine, so I decided to do that one day a couple months back. It was about-20F so I left it running and I went inside to let it get nice and warm. Once in the shop I realized that I did not turn on the electric fans. No reason to worry, I thought: it is damn cold out and that engine runs cool anyway.

Big mistake. I looked out the window not too much later and saw that steam was coming out of the hood. When I got to the truck the temp gauge was pegged and the top of the rad was cracked. I turned on the fans, pulled the cap off and added coolant to get the temp back down. Against all odds it does not seem like I damaged the engine: it runs fine... I think I got to it in time.

The rad, though, was another matter. I saw that it had failed at the top, near the upper rad hose. Looking closer it seems like it was an old farmer repair that had given way. It's a copper four core rad and I have no reason to believe that it is not original to the truck.

I pulled it and took it to the one remaining rad shop in my city to have it refurbished. The shop in question mostly works on rads for semis and Caterpillars so they need to be cajoled to do little jobs for me.

To those who may be wondering: the cost to repair it was roughly 95% of the cost to purchase a new aluminum one. In most cases that kind of equation would lead me to choose to simply replace the part altogether. But by fixing the old one I have an original copper rad that I know will fit in my truck: and I do not have to deal with shipping, damage in transit, or fighting with warranty if something is wrong with it. Being in Canada makes those issues important considerations. If there are any problems at all I just take it back out and bring it back to Kelly at the rad shop, I don't have to put it on a slow boat to China.

So, lesson learned. Hope to install this weekend.

[cornerstone]

Wise choice on the radiator. We have Kirby's Radiator in my area who is the go to for radiator work. The place has been at it forever. My kind of place.

Very cool truck man.

[dagnabbitt]

I installed the radiator yesterday. I took the opportunity to degrease, pressure wash, and repaint the electric fans, rad support, trans cooler etc.

I was thinking of spray bombing the grill again - the chrome is showing through - but ultimately decided to think about it. The PO made this choice and I have to assume that he did so because the chrome was in bad shape, but it isn't something I would have done. I am going to hunt around for a nicer grill for sure. I also have a 1967 grill which would look fine black since it was painted and never chrome, but my understanding is that I would have to change out a few other things to make it fit in a 72. So it stays as is for now.

It seems as though I will be driving the truck this week if it is warm enough, looking forward to that!

[dagnabbitt]

In what probably appears to be a continuing effort to throw good money after bad, I decided to replace the dual exhaust today.

I might have not mentioned that this truck was pretty dang loud when I got it. It just had straight pipes with cherry bombs that terminated right behind the cab, and although it did sound kind of cool at first, it sounded progressively less cool the more I drove it.

Because I need new cab corners it was actually louder in the cab when the windows were rolled up. The sound produced was not a nice rumble, either. More like a boiler that was about to explode.

When you take the exhaust "system" I just described and factor in the clatter of a 6.2L diesel in an uninsulated engine bay, it was pretty obnoxious.

I have been daily driving the truck about 50 miles a day - mostly highway and freeway - so I thought I would treat myself. It is new from manifold to tailpipe, with a pair of knockoff GM sedan mufflers, just dumping over the rear axle.

It is soooo much quieter. Last time I took my wife for a ride I gave her some earplugs, I am hoping she likes it better now.

[68Gold/white]

So, Dave,
What's next??? Just driving??? I'd enjoy driving that awesome pickup!!!

With the new exhaust does it still sound like a diesel???

[dagnabbitt]

I’m sorry for my late reply, yes it still sounds like a diesel, especially since the engine bay has virtually no insulation. It is far more tolerable now in the cab since it dumps behind the axle. But when I drive by it still sounds like a train car full of doorknobs going over a cliff!

I had a problem getting it started the other day and that led to checking the block heaters - I have ordered new cords - as well as a new starter. The starter is pretty tired and so it runs the battery down which in turn heats that starter up. I’ve learned that for a diesel in particular it just isn’t a good idea to have a weak link in your starting system. The one I ordered is off of Amazon, it looks to be made in USA and has good reviews. I’ll post some more pics when it arrives, and a link.

I hate to think someone stole it but the decal on one of my dually hub covers went missing so I ordered another off of eBay, luckily it was cheap.

Truck also needs a rear main seal so I guess I will be doing that too!

The 51 chev is not mine, it’s a friends I just like how they look together.

[68Gold/white]

I used to have a connection with a diesel shop, for the small (one ton) vehicles we worked on at my work's shop.
He recommended to replace a gear drive starter with the older direct drive starter because the direct drive starters actually spin the engine faster gear drive type. We performed such a swap many times, and it did help...

Let me know if you have any trouble getting the block heater cords. I may have some spares. I'd have to see the ends of your old ones to know for sure.

Tail pipes couldn't hurt the exhaust tone...

At my previous job (school bus dealer). We had a customer complaining about engine noise. The bus was a front engine transit type bus, the engine bay is next to the driver, has a dog house you lift up to get to engine. Very difficult to work on...........
My boss googles around and found a company that made insulating materials (I do not remember brand...). We bought a small roll of one inch theick flexible dense foam with a thick foil backing that also reflected heat. We put it on the back side of the engine cover, and a couple of other small areas. It made a HUGE difference in the noise level. I think you could accomplish the same with your diesel...some how...wouldn't take a lot of $$$ or time...mostly thinging of where to install. I'd at least cover the underside of the hood...

[dagnabbitt]

I did manage to find the block heater cords, and I am always looking for cheap sound deadening, I saw a thread where someone put something like that in the doors. I agree that I should be putting that under the hood. I wondering if it would help keep the sound down on the street, too, the hood itself vibrates pretty good with the engine running!

This past week I did replace the starter with this one, it claims to be completely new and not remanned, I guess we will see how it works.

Also replaced the rear main seal and oil pan seal. Had to jack the engine up to get at the oil pan seal. Just hoping to keep the mess on the street to a minimum.

I'm starting to wonder how many miles are on this engine, I wish there were options for rebuilding or replacing them but most people consider the 6.2 not worth working on.