Hi,

I have a problem with my 2002 Tahoe. On the dash my Tahoe the message center kept saying "Low Coolant", I filled it up and the next day it said "Low Coolant" again, and I looked and it was gone (not sure if I put enough in or not).
So I took the Tahoe to a mechanic and he said he couldn't find any leaks or anything. He put stop leak in it and tightened a few hoses. And steamed cleaned my engine to get more money

That was two weeks ago...

Yesterday I want on a 250 mile trip and I looked at my coolant tonight and it is down about 1/3 or maybe a little more from where it was filled up. The funny thing is it doesn't seem to be leaking when it is just sitting there only when the car is running... but it doesn't seem to be leaking that much, just enough.

Have any suggestions for what to look for and what might be going on?

 

bulletin No.: 06-06-01-019B

Date: June 12, 2007

INFORMATION

Subject:
Information on Gradual Coolant Loss Over Time With No Evidence of Leak Found
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(R) GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z - RPOs LR4, LM7, LH6, L33, L59)

Supercede:

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.

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 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).

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.

 

I have the same problem with my 01 GMC Yukon XL. No signs of leaks but I'm putting gallon in every week. Was told it could be the intake manifold gasket any others out there have the same problem. This is getting annoying having to put gallon every week. Anything would help. Hoping not to be a head. Don't hava alot of money now Unemployed.

 

The other thing is I've been told to replace the water pump the radiator but there was no sign of leaks.

 

if you can get ahold of a combustion gas leak detector it would be a 5min check if the head gaskets have a good leak

 

No coolant in the intake of 4.8, 5.3 or 6.0


That would be a waste of money. You can have coolant dye added to the system which will leave a obvious sign of an external leak.

 

Blown head gasket only shows up with a CO detector if the gasket is leaking into the combustion chamber.

It will not prove or disprove the above TSB

 

A gallon a week is going to show up somewhere if its leaking, check under the dash where the heater core is and if you have the rear system check the rear heater core...
It sounds more like 66impala4dr has a consumption issue not a leak...
That much should be showing up in your oil, is it looking milky?

Leaks on or at the top the engine you can usually smell, anything lower should be leaving signs on the ground.

 

it'd either show on the dipstick or the co tester

 

No milky oil.