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229 Posts
Discussion Starter · #1 ·
Hello all. This is a journal of the work done to our new family Suburban. I hope you find it interesting and informative. I will try to post pictures and be detailed about part numbers and other things as they come up. I hope to learn from all of you also.


229 Posts
Discussion Starter · #3 · (Edited)
Ok, let's start the way-back-machine to cover a little history. I am a long time Florida resident and lived all over the state. Growing up I was always taking things apart to discover their inner workings. Dad thought it would best if I was more constructive and put things together instead of the growing pile of "parts" I was making so I worked with him in his Construction business.

In 1992 my Dad purchased a 1982 GMC Suburban 1500 Sierra Classic with the 6.2L diesel for his construction company and that was the start of a beautiful friendship. At the time I was in high school and worked with him on the weekends, holiday breaks and in the hot summers here. I was his apprentice and was also in charge of all the vehicle maintenance for the family. The 6.2 diesel was different, but quickly became my favorite. I learned everything I could about diesel engines and how to keep them running. Also at the time our family enjoyed working on and showing our classic cars together. Being that we were in East Central Florida, we frequently attended classic car shows in Old Town Kissimmee, and Daytona.

About this time, I bought the 1982 Suburban from Dad and he got a shiny new 1994 Chevy dually 3500 with the 6.5 TD. This was another great truck that I learned a lot about. The factory turbo was the focus of a lot of learning and comparison to the Banks turbo for the 6.2L.

The other thing I got to do is travel quite a bit with my Dad, and after high school I wanted to see these great United States from the ground behind the wheel of a diesel, so I discovered trucking. I got my CDL while working in the moving business and started my adventures cross country as a long-haul mover. During my time driving, I got to see and operate many neat big trucks and owned a few myself.

I did moving for a long time and worked my way into high-value logistics, hauling everything from satellites for NASA to trade show stuff for Detroit. It was neat, but I really wanted to settle down and life on the road is tough when you have a family. So my next great adventure was about to start... Computers!

Computers were a real mystery to me, but after a few years of tinkering with them I figured them out. It led to jobs in the IT\IS industry and provided a pretty good living for a family. We have everything, but something was missing. My wife and I have been blessed with two daughters and a Boxer. Last summer, we loaded them all up in the car for trip to visit family in Wisconsin and we quickly discovered the missing things... room and comfort! That started the hunt for a larger family vehicle and triggered my memories of traveling with Dad in the Suburban.

After a year of solid researching\searching & looking at a lot of high-priced junk, we came to find a decent 1995 Chevy C2500 Suburban with the 6.5 TD from a man in Port Orange. The body and interior were in great shape and the engine seemed to be in good condition with 194K on the clock. We talked to the man and it seems that he inherited the Burb from his uncle and it was his wife’s daily driver. He wanted to sell it to start a lawn business as he couldn’t use the Burb.

We took it for a drive, and gave it a good looking over and only found a few issues for it being a 19 yr. old truck. The wife fell in love with it, and the kids liked it too, so we bought it from the man for $3200. We made the 100 mile trip home with only one issue related to CEL at about 70 MPH on I 95. Also the youngest daughter got her first nap in the new truck and we start a new family chapter!



229 Posts
Discussion Starter · #5 · (Edited)
Now that the Suburban is home, the work begins.

As a whole the Suburban seemed to be very well cared for by the previous owners and when looking under the hood it was apparent regular maintenance work was done to it. The Suburban is bone stock other than a remote mounted Stanadyne PMD and does not appear to have ever towed much as there was no brake controller or evidence that there had been one.

Starting off, I completed the checklist as it was not possible to complete everything in the FAQ for purchasing a 6.5 diesel. No issues were found, other than the CEL during the ride home. Fixing this was easy as it seems the small vacuum tube to the wastegate had come off. After a test run on I 95 at 70 MPH and over, the CEL did not come back on.

Next I gathered info on the VIN and RPO codes in the glove box and did some research on the truck in preparation for maintenance. The service provided by CompNine is pretty good so I ordered a report.

According to the report, the Burb was built on Tuesday 10/3/1995. >> For you history buffs, this was the day O.J. was acquitted for the murder of Nicole Brown Simpson, and her friend, Ronald Goldman.<<

Other highlights of the report:
- GU6 AXLE,REAR,3.42 RATIO 3.42R(GU6)

First order of business with any new car for me has always been fluid and filters.

- Changed the oil & oil filter
- Replaced the fuel filter
- Checked the air filter
- Checked the tyranny fluid again
- Noticed the rear end was leaking during the inspection; changed the rear differential fluid and cleaned up the differential cover
- Checked the coolant system as it seemed to take a long time to warm up
- Found rust in the cooling system, so the system will need to be flushed

229 Posts
Discussion Starter · #6 ·
I placed an order for parts from Rock Auto and went to work on the rear end first.

Here is what I learned about the rear end:

- 14 bolt semi-floating axle with a 9 1/2" drive gear
- G80 option positraction limited slip
- Fluid capacity is 2 3/4 quarts of 80-90W gear oil GL-4 & GL-5 rated
- Gasket for the differential cover is FEL-PRO RDS55387
- No limited slip additive was used as this is NOT recommended according to GM TSB #91-4-109

Once open the inside of the differential was clean with little metal on the magnet. The gears were sharp, meshing surfaces shiny and no play present (please note in the pict below, I pushed my finger into the magnet, making the metal stand up).

Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 75W-90 GL5 (P/N 12378261).

The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

VEHICLES/COMPONENTS INVOLVED: ----------------------------- Some light duty trucks equipped with locking rear axles, RPO G80.
Part Number Description ----------- ------------------ 12678261 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.

Pictures before, during and after


229 Posts
Discussion Starter · #7 ·

229 Posts
Discussion Starter · #8 · (Edited)
After replacing the coolant system quick connect tees comes the coolant system flush to remove the rust. Current flush kits are ok for cooling systems that are in good shape but not very effective for neglected systems. In the past, I have had great results using the now discontinued GM heavy duty flush kit. After doing some research, conversations with a friend who is a mechanic and some old-timers, we came up with a heavy duty flush kit like the old GM\Prestone one.

Below is the revised post about the heavy duty flush kit. The revisions are as follows:

- Updated the verified quantity of soda ash contained in the original kit from GM\Prestone
- Revised notes in the Acid & Neutralizer sections
- Added reminders between the Acid & Neutralizer sections

Update... successfully completed the 3 hour run part of GM TSB 99-06-02-012D, because I did not know if the previous owners mixed DEX-COOL and Ethylene Glycol at any point of the life of the truck.

No leaks and no overheating issues. Next step is drain the coolant system, refill with water, neutralize the acid, then flush the cooling system again. If the rust is gone, then replace the old thermostat & radiator hoses otherwise, it will be flushed again with acid for another 3 hours tomorrow.

By the way, they don't offer the heavy duty acid flush kit anymore but I was able to get a list of the ingredients and make my own. The original flush kit was offered by GM and Prestone and consisted of two parts; an acid part and an acid neutralizer part.
- GM Heavy Duty Cooling System Cleaner - part number 12346500 (discontinued)
- Prestone Heavy Duty Cooling System Cleaner - part number AS100 (discontinued)

The info on the ingredients is here.

These compounds to make your own heavy duty flush kit can be easily gathered from multiple sources.

- The acid part of the kit is Oxalic acid in 99% pure crystalline form
- When using the acid, the GM kit consisted of 9 oz (dry)
- The neutralizer part of the kit is soda ash in 99% pure crystalline form
- Verified - the neutralizer is 2 oz (dry)
- There are 5 other ingredients listed but account for less than 10% of the kit
- I believe these other ingredients were conditioners for the cooling system and are replaced with better compounds found in modern coolants and quality coolant additives such as Red Line Water Wetter

>>>> Drain the coolant before flushing the system <<<<

Acid Notes:
- Oxalic acid is an acid and should be respected :duh:
- It should be treated like oven cleaner (lye)
- When mixed with hot\warm water as described below and added to the cooling system, the solution has the same pH as vinegar
- Oxalic acid is eco-friendly, but the stuff it removes may not be
- Use gloves and goggles while handling the acid
- Don't breath hot steam from the coolant system as the acid can irritate your respiratory system
- Make sure to mix the acid crystals with hot or warm water to completely dissolve the crystals BEFORE adding it to the engine
- Wipe any spills immediately on glass as it can leave a mark; some people say it etches glass
- Remove all air in the cooling system using the bleed-valve; Air pockets in will not allow the acid to remove rust
- During warm-up time, suggest opening and leaving the coolant cap off to allow for "burping" of the coolant system
- When the cooling system has nearly reached temperature, put the coolant cap back on the reservoir, locking it in place
- Getting the engine to full operating temperature is key as heat acts as the catalyst necessary for full removal of the rust in the engine
- After running the specified period of time, allow the engine to cool burns, then drain the cooling system
- Let cool overnight if necessary
- Collect the waste as the acid is active and can bleach the surface under your truck
- If you have stains on the driveway from working on your truck, Oxalic acid is wonderful for getting impossible stains out
- If you have stains on your wood deck (from working on you truck?!? :uhoh2: :cookoo: ), Oxalic acid is great at renewing weathered wood as it is also known as Wood Bleach
- Oxalic acid can be used to remove orange rust commonly found on houses, buildings, sidewalks and toilets caused by hard water stains in well water systems
- Oxalic acid can be used to restore heavily rusted items and is safe for use on restoring rusted chrome

>>>> It may be necessary to reapply acid to flush heavy deposits in the cooling system. Drain acid and refill with new water\acid mix until all rust has been removed from the system<<<<

>>>> Drain the acid and refill with new water before using the neutralizer <<<<

Neutralizer Notes:
- Neutralizer part of the original GM\Prestone kit was Sodium Carbonate (Soda Ash, Washing Soda) and is used in water purification, disinfectants and soft drinks
- Soda Ash is a strong base and should also be respected :duh:
- Large (and high purity) concentrations can cause chemical burns on bare skin
- Soda ash is also eco-friendly and has multiple uses at home
- Use gloves and goggles while handling because the crystals are concentrated
- Make sure to mix the neutralizer with hot or warm water to completely dissolve the crystals BEFORE adding it to the engine
- Remove all air in the cooling system using the bleed-valve; Air pockets in the engine will react with the neutralizer and heat, causing pitting of aluminum!
- Getting the engine to full operating temperature is key again, as heat acts as the catalyst necessary for full neutralization of the acid
- Make sure to flush the cooling system thoroughly (multiple times) to remove all neutralizer
- Soda ash can be used in many areas of the house for cleaning and for laundry, removing grease effortlessly (my work shirts after a day under the Suburban)
- An alternate to using the Soda Ash (Sodium Carbonate) neutralizer like provided in the GM\Prestone kit, is Baking Soda (Sodium Bicarbonate)

>>>> Recommend using pH test after flush, neutralize and rinse is completed to verify pH is neutral (pH value of 7) BEFORE refilling with coolant <<<<

Hope this helps keep your ride going! :thumb: :flag:

229 Posts
Discussion Starter · #12 ·
Ok update time...

Following the 2nd cooling system acid flush, everything was put back together and refilled with water. I wanted to take it around down the road for a meeting as the wife was out.

The Burb fired up, ran for about a minute, then died. :thumbsdow

Popped the hood to find the tension pulley was wet with fuel. At the bottom of the fuel bleeder T-valve, the hose had cracked. :uhoh2:

Not really a surprise, because during removal of the T-stat housing I had to lift\stretch the fuel bleeder T-valve off the bolt as the line was a little short. The line was hard and brittle due to heat and age and after removing the T-valve, this was really visible.

I tried to plug the line with a screw then a bolt but the slippery diesel kept getting by. When trying to put a larger bolt or screw in the end of the tube, it would just split the line. Being crunched for time, I had to get a ride and leave the Burb at home.

A little disappointed but OK knowing it could be worse. I always figured its better to break down at home than out on the road or even worse, a breakdown for the wife out on the road. During my ride to the meeting with my buddy, I realized I have a problem with anything with at tee in the truck and will proceed accordingly in the future :HiHi:

So the next steps are in front of me; replace the fuel lines into & out of the FFM as the other lines are probably in the same condition. :thumb:


1995 GMC Suburban
18,226 Posts
Those lines are usually crack with age.

Imagine 20 years of heat and cold.
There is also a line to the IP from FFM.

While at it, you can raise the FFM, change the o-ring inside FFM and clean the FFM.
Then you can route the hoses above the intake.
Check the Fuel Leak thread recently, I posted the parts list there.

229 Posts
Discussion Starter · #14 ·
Fuel lines and FFM fun

Here is the steps for replacing the fuel lines in an out of the fuel filter manager (FFM) on my 1995 Suburban 6.5 turbo diesel.

Tools & materials used

- Time & patience
- Flat head screwdriver
- Needle-nose pliers
- Regular pliers
- 15mm deep socket & ratchet
- 4' of 1/4" fuel line (from the FFM to the IP & from the FFM to the bleeder T-valve)
- 2' of 3/8" fuel line (feed from the fuel tank tube to the FFM)
- 2' of 5/16 fuel line (return from the engine\injectors to the fuel tank)
- 18" nylon zip ties for holding wires & tubes back
- Roll of electrical tape
- Rags and paper towels
- Small flashlight
- >>>Camera phone<<<
- Pen and paper for notes

Before dismantling anything, I got great pictures of everything in the areas I would be working on. The camera phone was and continues to be one of the most important tools used for each job.

Removal Procedure

NOTE: The fuel filter was left in the FFM to keep junk from falling into it during removal

1. Examined and noted position of each of the (4) electrical connections on the metal bracket, hanging off the FFM
2. Disconnected each of the (4) electrical connectors & removed them from the metal bracket
3. Examined with the flashlight and noted the routing of the fuel lines & wiring harness above and below the FFM
4. Removed both of the 15mm bolts holding down the FFM
5. Lifted the FFM and removed the metal bracket used to hold the (4) electrical plugs
6. Lifting an tilting the FFM, studied each of the (3) fuel lines and noted their position
6a. FFM side closest to the front of the engine are (2) 1/4" connections and fuel lines
- The passenger side line goes to the fuel bleeder T-valve
- The driver side line goes to the IP
7. Removed each of the (3) fuel lines into the FFM using the flat screwdriver & flashlight to loosen the hose clamps for each
8. Carefully removed the FFM with a rag under it to catch spilling fuel
9. Zip-tied electrical plugs out of the way
10. Studied, noted and photographed the area behind the FFM
11. Removed the plug into the OPS and zip-tied it out of the way too
12. Removed the 3/8" fuel line from the fuel tank and the 5/16 return line using the regular and needle-nose pliers

This was a good place to stop & clean the valley out of accumulated junk. Found that the old shop-vac works well for this

At this point the all the old fuel lines were replaced as follows.
1. For the 1/4" lines from the FFM to the IP and T-valve that run under the intake manifold
1a. Cut the new 4' line in half, making (2) 2ft pieces
1b. Using the electrical tape, attached the end of the new lines to the old ones
1c. Pulled each new line under the intake manifold by pulling the old line out of the area where the FFM was
2. Cleaned then transferred the (3) hose clamps to each of the (2) new 1/4" fuel lines
2a. Attached the 1/4" to the IP inlet and tightened the hose clamp
2b. Attached the 1/4" to the T-valve, no hose clamp
2c. At this point the (2) new 1/4" fuel lines were under the intake, attached on one end, but not to the FFM
3. Measured, cut and replaced the 3/8" & 5/15" supply\return lines
- Using a bit of diesel fuel on the ends of the new lines helps get them on the ends of the metal fuel lines
- Found it necessary to reach behind\over\around the OPS with a couple of fingers to reposition the metal fuel tube and hold it while pushing the new tube on

The entire time to remove the FFM, old lines and replace with new took about 2 hours to complete while taking notes an photographing

Next up, will go through the FFM. But first some pictures :clap:


229 Posts
Discussion Starter · #15 ·
FFM area picts and number at the rear of the block

More picts of the rear engine and area under the FFM where the OPS, 3/8" and 5/16" lines are located.

Tried to look in the valley of the block to see the casting numbers but wasn't able to. In one of the pictures I took has a number with the last three digits of 141.

Is it possible to get the block casting number from here and is 141 a valid number? :confuzeld

If it is a 141 block, is that a decent one? :think:


229 Posts
Discussion Starter · #16 ·
Rebuilding the FFM

New fuel lines have gone in, and the FFM is ready for some attention before it goes back in.

Removed the new fuel filter and found the bottom of the FFM was covered in junk. Also found that the wire on the fuel heater was exposed. :eek: Time for a rebuild & repair!

Contacted the local GM dealer and had them order the (2) o-rings for the water in fuel sensor and fuel heater cap seals.

GM part numbers

- Water in fuel sensor seal 12511959 $2.02
- Fuel heater cap seal 12511962 $6.89

NOTE: Found after reassembly the fuel heater cap seal was a little too big :)confuzeld ??? :think:) and allowed fuel to leak. I ended up reusing the old o-ring with no leaks, but still looking for the correct replacement part

Noticed the FFM identifies where both of the 1/4" connections go to. No good when the FFM is installed because you can't see it! :think: :duh:


229 Posts
Discussion Starter · #18 ·
FFM rebuilding notes

Rebuilding the FFM was pretty straight forward.

1. Completely dismantled the FFM
2. Scrubbed all the non-electrical parts with soap and water
3. Dried well after cleaning
4. Inspected after cleaning
5. Part of the WIF seal was stuck on the body of the FFM; Using an old bronze brush from my rifle cleaning stuff, the old seal came off without damage to the seal area
6. Repaired fuel heater using high-temp RTV on the exposed wire of the fuel heater (discovered earlier), it sealed it up nicely

- The small on-tube filter was in good condition, so it will not be replaced
- Found many debris were still stuck to the bottom
- Tried to remove with a toothbrush, then pieces of a rag but the results were not good after 30 mins of trying to fight with 20 yrs of accumulation
- Took out to the front yard and fired up the pressure washer, successfully blasting all junk out in 2.5 seconds :D

After the pressure washer, I dried it again and blew out each of the inlets with compressed air to remove any hidden water and let dry overnight. Coated in WD40 to keep any rust at bay as this area is known for rust.

Next day, checked the FFM again and noticed the inside of the main filter tube had surface rust. Using a piece of steel wool and the drill on a low setting, the surface of the tube has no rust. Washed and dried it all again followed by a fresh coat of WD40 waiting for the o-rings to come in. :whistle:

While waiting, I took apart & cleaned the air filter, filter box, turbo inlet tube and CDR valve plumbing.

Here is a pict of the FFM body after soap and water, before the pressure wash:bat:


229 Posts
Discussion Starter · #20 ·
O-ring oops

The FFM o-rings arrived and were installed. I should have looked closer as the new o-ring in the fuel heater cap was a little larger than the old one and ended up causing a leak.

After discovering the leak I had to remove the FFM and install the old o-ring. Below are pictures that compare new and old after removing the FFM for the 2nd time.


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