I have recently been plagued by a coolant leak. Unlike most of the driving public. I enjoy spending time inspecting my truck inside and out from time to time. In search of dreaded Gremlins. They will occasionally grab on to ones vehicle and wreak havoc until they are exposed and killed. Today I have killed another one. I want to share with everyone the results of the autopsy.
? ? ?It is NOT a "Normal" thing for one to lose coolant. It can evaporate a VERY little bit over time but for the most part it will stay at the same normal level for years. When it starts to go down one should mark the bottle and begin a leak detection study first daily then weekly. In the event you have detected a leak this study where you make the coolant levels for a period of time will protect you and your truck from added extra expenses. 98% of the time the root cause of a coolant leak will be a Water pump seal failure roughly around 70,000 miles. It happens. I know this. GM knows this. Any mechanic that has ever worked on the generation III 5.3L engine knows around 70,000 miles your water pump seal will fail. (Incidentally this was supposedly resolved in the generation IV engines) It is also a "Normal" thing for a certain amount of burping to occur shortly after the replacement of a water pump. The 5.3L engine wasn't designed with a pressure relief valve to aid in the relief of air in the normally coolant only environment of the water jacket on your engine. So what will occur for the first couple of weeks after that repair is coolant will be replaced with air in the overflow bottle while it is burping. This is all considered "NORMAL." If you take it back to your dealership they will top it off and all will be well.
? ? ?What happened to me was shortly after the replacement of my coolant pump I continued to leak coolant. Despite it being topped off twice for 3,000 miles. That is well beyond a "NORMAL" period for it to burp. I asked the dealership to conduct a pressure test. They pressurize the system if it holds pressure for an hour it is declared passed. My truck passed. But it was still leaking coolant! I continued my leak study for a couple of more weeks, and was able to calculate a coolant loss of 3-6 oz per week. I was also able to make a correlation between the number of miles I drive VS: the rate of coolant loss. The more I drove The more I lost coolant. That told me that whatever the problem was. It was occurring while it was under pressure. This indicates to me that I have a pinhole leak somewhere in the waterjacket or the cylinder head. Not any of the seals because I can observe them under direct observation. I took it back to my dealership...PROBLEM!!!
? ?I had a GMPP Majorguard Policy that covered me to 76,124 miles. I had the water pump replaced at 74,500 miles. SO it was covered. I now have 78,421 miles so I am now out of warranty. And am looking at a potentially costly leak somewhere in the water jacket of the engine. I return to my dealership. I spoke to the mechanic that fixed the water pump, because at that time he and I were now on first name basis. I asked him to conduct research for a no evidence coolant leak before he started going crazy. I spoke to the management of the dealership. Because I brought the truck to them originally for a "customer complains of coolant loss" they detected the actually leaking water pump. I detected the burping, and made them write it up when they refilled the bottle as a "Customer complains of coolant loss" So now that's 2 documents before the GMPP warranty expires. Once I went over the line and still had a coolant loss they agreed to cover the expenses of the repair and rental car.
Here is the TSB notice the title really closely and you can see it's not very old but no one really knows about it yet...
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Models:
2004-2006 Buic Rainier
2001-2006 Cadillac Escalade
2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, and Trailblazer
2001-2006 GMC Envoy, Jimmy, Sierra, and Yukon
2001-2005 Oldsmobile Bravada
2005-2006 SAAB 9-7X
With 4.8L or 5.3L VORTEC GenII, GenIV; V8 engine (VIN's V,T,M,M,Z --RPO's LR4, LM7, LH6, L33, and L59
Information:
Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.
Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.
Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.
Refer to the following illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.
If the cylinder head(s) is a Castech casting (1), inspect the area around the five oil drain holes for witness marks indicating coolant seepage over time (2).
Important: If No evidence of coolant loss is found on inspection of Castech casting cylinder head(s), follow normal diagnostic procedures in SI to determine the cause of the coolant loss.
The crack location can be found in any of the five cylinder head(s) oil drains. This can be seen as a clean or shiny area, on an otherwise stained surface (1). Pressurizing the cooling system at this time may reveal coolant, air, or a combination, weeping in the described area. If inspection reveals evidence of coolant witness marks (1), replace the entire cylinder head(s) assembly.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION?
? Copyright General Motors Corporation. All Rights Reserved.
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? ? ?I do not have pictures available yet. However when the Technician pressurized the system It was clear blatant and obvious exactly where the leak was. Right at the leading edge of the oil drain in the cylinder head. It was as if the pictures in the TSB were taken from my truck. The TSB calls for both cylinder heads to be replaced, and as such they are doing so at no cost to me. I did ask about port and polishing them while they were at it but they politely declined. I will tell you that I do conduct my own oil changes, and I inspect the oil every time. I did not detect any coolant or water in it. Nor did I detect any frothing in the oil a tel-tail signs of coolant in the oil. It was explained to me that what was occurring that a lot of the coolant was evaporating on the coolant head, and the rest a stronger more viscous version of the coolant was leaking back down to the oil so it wasn't churning like one would expect. If I can get some picture I will try my best but I think there is more than enough information to diagnose and resolve this problem. Any questions just ask.
JB
? ? ?It is NOT a "Normal" thing for one to lose coolant. It can evaporate a VERY little bit over time but for the most part it will stay at the same normal level for years. When it starts to go down one should mark the bottle and begin a leak detection study first daily then weekly. In the event you have detected a leak this study where you make the coolant levels for a period of time will protect you and your truck from added extra expenses. 98% of the time the root cause of a coolant leak will be a Water pump seal failure roughly around 70,000 miles. It happens. I know this. GM knows this. Any mechanic that has ever worked on the generation III 5.3L engine knows around 70,000 miles your water pump seal will fail. (Incidentally this was supposedly resolved in the generation IV engines) It is also a "Normal" thing for a certain amount of burping to occur shortly after the replacement of a water pump. The 5.3L engine wasn't designed with a pressure relief valve to aid in the relief of air in the normally coolant only environment of the water jacket on your engine. So what will occur for the first couple of weeks after that repair is coolant will be replaced with air in the overflow bottle while it is burping. This is all considered "NORMAL." If you take it back to your dealership they will top it off and all will be well.
? ? ?What happened to me was shortly after the replacement of my coolant pump I continued to leak coolant. Despite it being topped off twice for 3,000 miles. That is well beyond a "NORMAL" period for it to burp. I asked the dealership to conduct a pressure test. They pressurize the system if it holds pressure for an hour it is declared passed. My truck passed. But it was still leaking coolant! I continued my leak study for a couple of more weeks, and was able to calculate a coolant loss of 3-6 oz per week. I was also able to make a correlation between the number of miles I drive VS: the rate of coolant loss. The more I drove The more I lost coolant. That told me that whatever the problem was. It was occurring while it was under pressure. This indicates to me that I have a pinhole leak somewhere in the waterjacket or the cylinder head. Not any of the seals because I can observe them under direct observation. I took it back to my dealership...PROBLEM!!!
? ?I had a GMPP Majorguard Policy that covered me to 76,124 miles. I had the water pump replaced at 74,500 miles. SO it was covered. I now have 78,421 miles so I am now out of warranty. And am looking at a potentially costly leak somewhere in the water jacket of the engine. I return to my dealership. I spoke to the mechanic that fixed the water pump, because at that time he and I were now on first name basis. I asked him to conduct research for a no evidence coolant leak before he started going crazy. I spoke to the management of the dealership. Because I brought the truck to them originally for a "customer complains of coolant loss" they detected the actually leaking water pump. I detected the burping, and made them write it up when they refilled the bottle as a "Customer complains of coolant loss" So now that's 2 documents before the GMPP warranty expires. Once I went over the line and still had a coolant loss they agreed to cover the expenses of the repair and rental car.
Here is the TSB notice the title really closely and you can see it's not very old but no one really knows about it yet...
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GM TSB# 06-06-01-019B (came out 06-12-2007)
Subject: Information on Gradual Coolant Loss Over Time With NO EVIDENCE OF LEAK FOUND
Subject: Information on Gradual Coolant Loss Over Time With NO EVIDENCE OF LEAK FOUND
Models:
2004-2006 Buic Rainier
2001-2006 Cadillac Escalade
2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, and Trailblazer
2001-2006 GMC Envoy, Jimmy, Sierra, and Yukon
2001-2005 Oldsmobile Bravada
2005-2006 SAAB 9-7X
With 4.8L or 5.3L VORTEC GenII, GenIV; V8 engine (VIN's V,T,M,M,Z --RPO's LR4, LM7, LH6, L33, and L59
Information:
Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.
Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.
Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.
Refer to the following illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.
If the cylinder head(s) is a Castech casting (1), inspect the area around the five oil drain holes for witness marks indicating coolant seepage over time (2).
Important: If No evidence of coolant loss is found on inspection of Castech casting cylinder head(s), follow normal diagnostic procedures in SI to determine the cause of the coolant loss.
The crack location can be found in any of the five cylinder head(s) oil drains. This can be seen as a clean or shiny area, on an otherwise stained surface (1). Pressurizing the cooling system at this time may reveal coolant, air, or a combination, weeping in the described area. If inspection reveals evidence of coolant witness marks (1), replace the entire cylinder head(s) assembly.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION?
? Copyright General Motors Corporation. All Rights Reserved.
--------------------------------------------------------------------------------------------------
? ? ?I do not have pictures available yet. However when the Technician pressurized the system It was clear blatant and obvious exactly where the leak was. Right at the leading edge of the oil drain in the cylinder head. It was as if the pictures in the TSB were taken from my truck. The TSB calls for both cylinder heads to be replaced, and as such they are doing so at no cost to me. I did ask about port and polishing them while they were at it but they politely declined. I will tell you that I do conduct my own oil changes, and I inspect the oil every time. I did not detect any coolant or water in it. Nor did I detect any frothing in the oil a tel-tail signs of coolant in the oil. It was explained to me that what was occurring that a lot of the coolant was evaporating on the coolant head, and the rest a stronger more viscous version of the coolant was leaking back down to the oil so it wasn't churning like one would expect. If I can get some picture I will try my best but I think there is more than enough information to diagnose and resolve this problem. Any questions just ask.
JB