Cooling System - Coolant Leak At Surge Tank
TECHNICALBulletin No.: 11-06-02-002A
Date: September 11, 2012
Subject: Coolant Leak at Surge Tank, Radiator Surge Tank Cap Leak, Coolant Not Transferring from Surge to Overflow Section of Tank or Possible Engine Overheating Condition
Models:
2011-2012 Chevrolet Silverado HD 2500-3500
2011-2012 GMC Sierra HD 2500-3500
Equipped with 6.6 L Duramax(R) Diesel Engine (RPO LML or LGH)
Supercede:
This bulletin is being revised to update the Subject, Condition, Cause and Correction sections. Please discard Corporate Bulletin Number 11-06-02-002 (Section 06 - Engine/Propulsion System).
Condition A
Some customers may comment that there is coolant leaking, or the appearance of a coolant leak, from the coolant surge tank area of the vehicle. This leak may be around the fill cap or hose areas.
Condition B
The coolant from the overflow side of the surge tank assembly may not transfer to the surge tank side when the engine is thermo-cycled.
Cause A
The coolant may be residual from a recent service, leaking out of the tanks atmospheric vent, or a coolant surge tank hose, cap or tank leak.
Cause B
The coolant surge tank to cap interface may not allow the transfer of coolant from the overflow side to the surge tank side.
Surge Tank Description
This surge tank is actually two chambers connected together (a surge tank and an overflow bottle). The front chamber (closest to the engine) is the surge tank and is the highest point of the coolant system. It uses a threaded pressure cap, similar to the one used on a radiator or engine fill system. The rear chamber (closest to the fender) is the overflow bottle. This is the air space in the cooling system where the coolant can expand into and contract from.
During vehicle use, the coolant heats and expands. The increased coolant volume can, in some conditions, push past the pressure cap and through a channel into the overflow bottle. As the coolant circulates, air is allowed to bubble out. This air is then transferred to the overflow bottle, through the surge tank cap, where it returns to the atmosphere. Coolant without air bubbles absorbs heat much better than coolant with bubbles. When the engine cools, the coolant, without air bubbles, contracts back into the surge tank from the bottom of the overflow bottle. As the engine temperature increases, the coolant in the overflow bottle side should increase and as the engine temperature decreases, the coolant in the overflow bottle side should decrease with the pressurized side of the surge tank remaining full (see below). If it is not functioning in this manner, there is a problem with the system and requires additional diagnostics.
Important
It is critical that the cooling system is filled completely following the instructions in SI under "Cooling System Draining and Filling." The "Vac-N-Fill Diesel" SI procedure is preferred. Make sure to completely fill the surge tank side of the coolant bottle to the "MAX" fill line (mid-year 2012 the max line was removed. Fill bottle to minimum line).
Additional information:
Surge Tank Cap - The cap for this surge tank should have an "R." Gasoline engine trucks have an "S" on the cap. Inspect for this when diagnosing the coolant leak.
Coolant Tank Seam - The outer seam between the upper and lower portion of the coolant bottle is not sealed. If any coolant gets on the outside of the bottle, it can seep into this seam and give the impression that the tank is leaking. This seam is part of the outer cover and is open to the atmosphere. Any coolant in this area is most likely not from a leak in the seam. Refer to the photo below.
Active Bleed Cooling System Hoses
Any time the cooling system is serviced on trucks built prior to October 16, 2011, install the active bleed cooling hoses (if not already installed). Inspect the truck prior to repair to verify the updated hoses have not already been installed.
If the hose update is required, use the following procedure to install the active bleed cooling system hoses.
1. Following SI instructions, remove the inlet heater hose and the surge tank inlet hose.
2. Install the new heater hose and surge tank hose connecting the new active bleed portion of the surge tank hose to the heater hose (shown above).
3. Follow SI instructions for "Cooling System Draining and Filling (Static Fill LGH, LML)" or "Cooling System Draining and Filling (Vac-N-Fill Diesel)" with the Vac-N-Fill procedure preferred. Ensure the correct radiator cap adapter is used (J-42401 Radiator Cap and Surge Tank Test Adapter).
4. The coolant bottle surge tank side must always be filled to the Max line on the surge tank side (later build 2012 had the Max line removed. Fill bottle to minimum line).
5. The overflow side should be filled approximately 1/3 cold.
Correction A
Use the following steps to diagnose and correct the condition.
1. Determine if there is a leak or if the coolant residue is the result of a recent service procedure or vehicle pre-delivery inspection. Refer to Loss Of Coolant in SI to help determine if there is a cooling system leak.
1. If there is no leak identified, the coolant may be escaping through the atmospheric vent. To prevent coolant from escaping from the atmospheric vent, insert a piece of 9 mm OD windshield washer rubber hose, approximately 100 mm (4.0 in) long, into the vent shown in the above graphic.
2. The hose must have an interference fit and extend at least 40 mm (1.5 in) into the reservoir bottle. Using coolant as a lubricant and twisting the hose will help during installation.
3. Route the hose and twist it so the natural curve is routed up and towards the rear of the truck as shown in the above graphic.
2. If the coolant is leaking at a surge tank supply or return hose, replace the spring type hose clamps with locally sourced, high quality screw type clamps.
3. If a leak is identified in the surge tank, inspect the cap for an "R." If an "S" cap is found, replace the cap with the proper cap. If an "R" is found, replace the tank and the cap. Only replace the appropriate parts if diagnostics indicate an actual leak.
4. Clean the coolant residue with water.
Important
It is critical that the cooling system is filled completely following the instructions in SI under "Cooling System Draining and Filling." The "Vac-N-Fill Diesel" SI procedure is preferred. Make sure to completely fill the surge tank side of the coolant bottle to the "MAX" fill line (mid-year 2012 the max line was removed. Fill bottle to minimum line).
Correction B
Use the following steps to diagnose and correct the condition.
1. Allow the system to cool down.
2. Clamp off the lower surge tank hose.
3. Remove the upper surge tank hose.
4. With the cap installed, using a vacuum producing tool (such as a Mighty Vac), attempt to pull a vacuum through the upper surge tank hose.
5. A properly operating cap and tank will pull coolant from the overflow side.
6. This can be verified by observing the coolant transferring from the overflow side to the pressurized side along with the coolant volume reducing on the overflow side.
If coolant is drawn from the overflow side, the system is operating correctly.
- If coolant does not transfer, pressure test the coolant cap following SI instructions.
- If the cap tests good, replace the cap and surge tank assembly.
7. Clean all coolant residue off of the engine compartment focusing on the coolant bottle. Makes sure there is no coolant in the seam of the coolant bottle.
8. Run the vehicle to operating temperature and verify the system pressure increases properly with no leaks (focusing on the coolant bottle seam).
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table.
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