What's Happening?

[BG46]

for the past few months i'm having to add coolant to my resevior as my "low coolant light" has been coming on.

i had a local garage do a pressure test and they found no leaks.

this past week i've noticed when i start the truck after sitting for a while there is a rather larger puff of white smoke coming out of the exhaust. it seems to have a faint aroma of coolant (don't know if that is true or my mind playing tricks).

can the coolant be leaking into the engine and cause this problem or is there some other explanation?

it's a 2003 GMC yukon xl if that helps.

thanks

[Bish]

Could be intake manifold gasket. I know the older ones had problems but I thought the newer ones did not.

[jacko207]

Could also be head gaskets or a bad cylinder head. Coolant can leak into the cylinders after the engine is shut off and then gets pushed out the exhaust on start up. I've had the same problem with an 04 Silverado.

There's a service bulletin for heads with a bad casting.

 

 

Subject: Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found #06-06-01-019B - (06/12/2007)

 

 

 

Models: 2004-2006 Buick Rainier

 

2001-2006 Cadillac Escalade Models

 

2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models

 

2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models

 

2001-2004 Oldsmobile Bravada

 

2005-2006 Saab 9-7X

 

with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z -- RPOs LR4, LM7, LH6, L33, L59)

 

 

 

 

--------------------------------------------------------------------------------

 

This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).

 

 

--------------------------------------------------------------------------------

 

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.

 

 

 

 

 

Cylinder head(s) location of the Castech manufacturing casting logo (1).

 

 

 

 

 

Close up view of the cylinder head(s) showing the Castech manufacturing casting logo (1).

 

 

 

 

 

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.

[98 Z71 SLT]

Could be intake manifold gasket. I know the older ones had problems but I thought the newer ones did not.

 

CANNOT be his intake manifold gasket. These newer engines have a "dry" intake...meaning there is NO coolant running through them.

 

If you have absolutely NO SIGNS of external coolant loss, you have cylinder heads with hairline cracks in them.

 

Stop off at your GM dealer, talk to the engine tech. Add some GM coolant dye to your recovery bottle. Drive it for a week or two, pull off both valve covers. Then, take a flourescent light and shine the light on the exposed head surfaces. That will tell if you have hairline cracks in the cylinder heads.

[marko]

for the past few months i'm having to add coolant to my resevior as my "low coolant light" has been coming on.

i had a local garage do a pressure test and they found no leaks.

this past week i've noticed when i start the truck after sitting for a while there is a rather larger puff of white smoke coming out of the exhaust. it seems to have a faint aroma of coolant (don't know if that is true or my mind playing tricks).

can the coolant be leaking into the engine and cause this problem or is there some other explanation?

it's a 2003 GMC yukon xl if that helps.

thanks

 

It's either a headgasket issue or a cracked head. Unfortunately

[jnbkosmo]

On my 03 Avalanche w/ the 5.3 my water pump was leaking while running and dripping onto the exhaust.My service rep said that it would boil off and that was why I would never see any drips.No problems after the water pump was replaced.

[BG46]

On my 03 Avalanche w/ the 5.3 my water pump was leaking while running and dripping onto the exhaust.My service rep said that it would boil off and that was why I would never see any drips.No problems after the water pump was replaced.

 

 

 

thanks for all the replies.

guess i better get it into the dealer and checked out before something more serious happens.