2007 GMC 2500HD HEATER CORE PROBLEMS!! help

LS1MIKE- thanks for the info.yea that must be what is formed in the overflow tank in my 2003 tahoe

TSB #00-06-02-006D: Engine Coolant Recycling and Warranty Information (Aug 15, 2006)
Portion of the bulletin that talks about Sealing Tabs and Dex-Cool

Sealing Tablets
Cooling System Sealing Tablets (Seal Tabs) should not be used as a regular maintenance item after servicing an engine cooling system. Discoloration of coolant can occur if too many seal tabs have been inserted into the cooling system. This can occur if seal tabs are repeatedly used over the service life of a vehicle. Where appropriate, seal tabs may be used if diagnostics fail to repair a small leak in the cooling system. When a condition appears in which seal tabs may be recommended, a specific bulletin will be released describing their proper usage.

Water Quality
The integrity of the coolant is dependent upon the quality of DEX-COOL® and water. DEX-COOL® is a product that has enhanced protection capability as well as an extended service interval. These enhanced properties may be jeopardized by combining DEX-COOL® with poor quality water. If you suspect the water in your area of being poor quality, it is recommended you use distilled or de-ionized water with DEX-COOL®.

"Pink" DEX-COOL®
DEX-COOL® is orange in color to distinguish it from other coolants. Due to inconsistencies in the mixing of the dyes used with DEX-COOL®, some batches may appear pink after time. The color shift from orange to pink does not affect the integrity of the coolant, and still maintains the 5 yr/150,000 mile (240,000 km) service interval.

Back Service
Only use DEX-COOL® if the vehicle was originally equipped with DEX-COOL®.

Contamination
Mixing conventional green coolant with DEX-COOL® will degrade the service interval from 5 yrs./150,000 miles (240,000 km) to 2 yrs./30,000 miles (50,000 km) if left in the contaminated condition. If contamination occurs, the cooling system must be flushed twice immediately and re-filled with a 50/50 mixture of DEX-COOL® and clean water in order to preserve the enhanced properties and extended service interval of DEX-COOL®.

After 5 years/150,000 miles (240,000 km)
After 5 yrs/150,000 miles (240,000 km), the coolant should be changed, preferably using a coolant exchanger. If the vehicle was originally equipped with DEX-COOL® and has not had problems with contamination from non-DEX-COOL® coolants, then the service interval remains the same, and the coolant does not need to be changed for another 5 yrs/150,000 miles (240,000 km).


Think about the head gaskets
TSB #05-06-02-001: Information on Aluminum Heater Core and/or Radiator Replacement

The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be preformed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant effectiveness.

Technician Diagnosis•Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating balls) will not completely analyze the coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be flushed.

•Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for component location and condition for operation.

•Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant. Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed, drained, cleaned and reinstalled before refilling the system.

Flushing Procedures using DEX-COOL®

Important: The following procedure recommends refilling the system with DEX-COOL®, P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. This coolant is orange in color and has a service interval of 5 years or 240,000 km (150,000 mi). However, when used on vehicles built prior to the introduction of DEX-COOL®, maintenance intervals will remain the same as specified in the Owner's Manual.
•If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions.

•If approved cooling system flush and fill machine is not available, drain the coolant and dispose of properly following the draining procedures in the appropriate Service Manual. Refill the system using clear, drinkable water and run the vehicle until the thermostat opens. Repeat and run the vehicle three (3) times to totally remove the old coolant or until the drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with DEX-COOL®, P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M, following the refill procedures in the appropriate Service Manual.

•If a Service Manual is not available, fill half the capacity of the system with 100% DEX-COOL®, P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. Then slowly add clear, drinkable water (preferably distilled) to the system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and reverify the coolant level. If necessary, add clean water to restore the coolant to the appropriate level.

Once the system is refilled, reverify the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. The concentration levels should be between 50% and 65%.

From GM Techlink March 2004:



Cooling System Seal Tabs What’s made of ground-up ginger root, almond shells and binder? And causes confusion in auto service departments?

Some people call them coolant pellets, but the proper name is Cooling System Seal Tabs. And we hope to clear up some misunderstandings about them.

How They Work
Seal tabs are dissolved in the engine coolant and the resulting fibres circulate through the cooling system. At a microscopic level, the tabs break down into irregular, long, thin fibres. When a small leak or seepage occurs, the coolant carries the fibres into the opening, where they cluster up and jam together. (Think of logs and branches in a beaver dam.) This mechanism is very effective at stopping leaks. Any fibres that make it to the surface will crust over and enhance the seal.

This sealing method is useful only for small-scale leaks and seepage, and tends to work best in conditions where the surrounding parts aren’t moving. The seals tend to break down in areas between metals that are expanding and contracting with temperature changes, for instance.

A Secondary Benefit
The traditional green-colored coolant, used until DEXCOOL® was introduced in 1996, contained silicates, which deposit on cooling system surfaces. The tiny fibres from the seal tabs acted as scouring pads, removing silicate deposits from the water pump seal faces, which contributed to longer water pump seal life.

Side Effects of Seal Tabs
In addition to the benefits of sealing small leaks and scrubbing silicates from water pump seals, seal tabs also have some side effects.

After awhile, a brown, dirty-looking stain may form on translucent coolant bottles. Residue may form on the backside of the radiator cap. And deposits that resemble rust may be found in the cooling system.

These are not problems, in the sense that they cause no physical harm. But their appearance can be alarming, especially on a new vehicle. Both customers and well-intentioned technicians can be misled by these deposits.

Another side effect comes from overuse. When seal tabs are used in the prescribed amounts, they will not cause restrictions or plugging in an otherwise properly operating cooling system.

But, if a little is good, a lot must be better. Wrong!! Overuse can lead to plugging, especially in the relatively small tubes used in heater cores.

Some History
There was a time when seal tabs were installed in every new vehicle, at the factory, to account for the inevitable small leaks that occur in castings, joints, and so on. By the mid ‘90s, manufacturing and machining techniques had improved to the point where the seal tabs were no longer needed on a universal basis.

With the introduction of long-life coolant, silicate deposits were no longer a concern, so the scrubbing action from the seal tab fibres was no longer needed.

TIP: GM plants, as well as other manufacturers, still occasionally use seal tabs to address specific concerns.

Today’s Recommendations
In short, GM no longer endorses universal use of seal tabs. Procedures in SI have been specifically written to discourage their use in most cases.

When a condition appears in which seal tabs may be beneficial, a specific bulletin is released, describing their proper use. One such bulletin is Customer Satisfaction Program 03034, dated 7/7/03. This applies to specific 3.8L engines only, and is in effect until July 31, 2005.

TIP: After performing the procedure in the bulletin, be sure to install a recall identification label to the vehicle to indicate that the seal tabs have been installed.

TIP: If seal tabs were installed in a vehicle at the factory, it’s OK that the proper amount of tabs be installed if the coolant must be drained and replaced.

What’s a Recommended Dose?
TIP: Use this information only when instructed to do so by bulletin or SI procedure.

The proper number of Cooling System Seal Tabs depends on the capacity of the vehicle’s cooling system. Use between 1 and 1 1/2 grams of tabs per liter of cooling system capacity.

TIP: Cooling System Seal Tabs are packaged in two sizes.12378254 Small tabs (4 grams each) 5 tabs per package
3634621 Large tabs (10 grams each) 6 tabs per package


It is most likely that your 03 had the tabs installed at the factory accounting for your residue in the overflow tank. It is pretty common prior to 2004.
GM discouraged the used after 2004.

jbres wrote:
ahhh! not fun. The reason I agreed to go with the universal stuff, was because I flushed my 2003 Tahoe WITH THE DEX COOL at 100k, and at 130,000 I had to replace a water pump. And when you look into the overflow tank, that red dex is gunked up on the walls. So I thought hell I might as well give it a try with the universal stuff on my 2007 GMC 2500hd.
There goes my $1,000 Christmas Bonus, lol. O well, could be a lot worse.

That is pretty good life out of an LS water pump. They have updated them over the years. Your 07 pump is better than your 03.

ahhh! not fun. The reason I agreed to go with the universal stuff, was because I flushed my 2003 Tahoe WITH THE DEX COOL at 100k, and at 130,000 I had to replace a water pump. And when you look into the overflow tank, that red dex is gunked up on the walls. So I thought hell I might as well give it a try with the universal stuff on my 2007 GMC 2500hd.
There goes my $1,000 Christmas Bonus, lol. O well, could be a lot worse.

2003silverado wrote:
There are only 2 times I can think of that I would use Bars Leak...If we were stranded 200 miles from the nearest civilization and my wife was going into labor, or I was just trying to limp a vehicle to the salvage yard.

I don't want anything in my engine that is designed to plug things.

X2

Time to take it to a GOOD shop, be it a dealer or service center. This is not going to be a easy nor cheap fix. I would request that I get the old heater core back even if it cost you a core charge. Then carefully cut it open and see just how plugged up it is. The fact that you let a shop flush it and swap out the DEX Cool makes it on you even if there was some kind of GM coverage.

Keep the core cut it open and see what it looks like, my bet it's all plugged up.

Don

There are only 2 times I can think of that I would use Bars Leak...If we were stranded 200 miles from the nearest civilization and my wife was going into labor, or I was just trying to limp a vehicle to the salvage yard.

I don't want anything in my engine that is designed to plug things.

Sorry for your troubles, GM may have had some bad Heater cores that year. It happened to my 2007 2500HD too 79,000 miles, its a large project to replace good luck.

jbres wrote:
Thanks for the replies..
LS1MIKE- I agreed to switch over to Valvoline Max Life, because I did some research on it, and it seems lots and lots of people switch from the Dex cool (aka dex death), to the universal yellow stuff.
After the flush, all was well for 1 year and 10,000k miles. Was this a fluke, or should I directly blame it to switching away from the DEX COOL?

Hard to say, depends on how long the original stuff had been mixed with the incorrect coolant.
Also depends on how good the flush was. They need to get it ALL out. At this point don't switch back. Fix the heater core, do a COMPLETE flush and put the universal stuff back in.

So much miss information on DEX out there. With the LS series of engines. 4.8, 5.3, 6.0, 6.2 etc. Leave the Dex in there. It does not cause any problems.

Thanks for the replies..
LS1MIKE- I agreed to switch over to Valvoline Max Life, because I did some research on it, and it seems lots and lots of people switch from the Dex cool (aka dex death), to the universal yellow stuff.
After the flush, all was well for 1 year and 10,000k miles. Was this a fluke, or should I directly blame it to switching away from the DEX COOL?