Coolant Loss 4.8 & 5.3 Vortec GM
 

Has this been around before ?

GM V8 Losing Coolant With No Apparent Leak

If your General Motors SUV or truck is losing coolant, with no visible signs of a leak, the source may shock you
Worse, allowing the problem to go on may well mean a new engine.

On several occasions General Motors vehicles, with the 5.3L and 4.8L engines have come to use because of a coolant leak. There is no outward signs of coolant leakage, yet the coolant reservoir keeps going low. The source of the leakage is the cylinder head(s).

Between 2001 and 2006 GM manufactured millions of vehicles, several with defective cylinder heads. The cylinder head castings were not properly done and over time they crack. The cracks often appear in the area of the center row of head bolts. This is under the engine valve cover and difficult to diagnose. Since coolant is leaking into the engine oil, a great deal of damage can quickly occur.

There will be few other outward signs other than coolant loss. Since this is coolant leaking into the oil and not water, there is normally be no clouding of the engine oil. Glycol is absorbed by the oil, but destroys the lubricating qualities of the oil. The crack also does not extend into the combustion chamber. There will not be an overheating problem, unless the coolant gets low and the radiator will not be over pressurized.

GM acknowledges the following vehicle can be affected. Unfortunately, other than standard warranty coverage, they seem unwilling to do anything about it.
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


One of the easiest ways to identify the problem is with florescent dye, added to the coolant. Another is to remove the valve covers and check for coolant contamination. Steam in the valve cover area will make this quite apparent. There will usually NOT be clouding of the remainder of the engine oil. (please click images for closer view)

Normal valve cover on top, coolant contaminated cover on bottom

Coolant contamination of oil in GM 5.3L valve cover

The affected heads have a casting mark, just above the intake port. Cylinder heads with this mark are the ones that may be prone to cracking. The cracks form in the five head bolt/oil drain areas, under the valve cover.

Areas prone to cracking and the identifying casting mark

Coolant leaking GM cracked cylinder head, disassembled and cleaned
The crack develops due to a poor casting and allows coolant to seep into the engine oil
On this stripped down and cleaned head the crack can actually be seen. With the head on the vehicle and assembled, it is quite difficult to see. A pressure test with the valve cover off will verify the problem. Coolant and/or air can normally be seen seeping from the area. Florescent dye and a black light makes this much easier. (please click on image for a closer view)

Proper repair involves replacement of the bad head(s). Several oil changes, in quick succession, will be needed clear the engine of coolant contamination. About every 1,000 miles for three-changes usually works. Coolant left in the engine will destroy the oil’s ability to prevent wear. Coolant in the oil will also greatly increase sludge buildup.

If you own a General Motors 4.8L or 5.3L Vortec engine and are losing coolant, don’t take a chance. AGCO can quickly diagnose and document the problem for you and repair any problem as well. AGCO, it’s the place to go!

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

1/3 of the vehicles they listed never came with a 4.8 or 5.3, and the block architectures from the 4.3's (or 4.2 I6's), is completely different.

The 4.2's DID actually have some coolant usage, head, and exhaust cracking issues.

What you posted read like an ad; just masquerading under a "consumer alert".

There is some "mysterious" coolant usage on some trucks with those motors, The TSB was titled "Coolant loss with no visible leak", and the trucks that have the problem can be identified by the vin (dealer will have, possibly alldata but I don't have that anymore). Just don't run to the dealer tho....its kinda like when the news tells you

Tonight at 9, something in your garage could kill you....tune in at 9 to find out.

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

I knew you would calm me down !!
Thanks for the quick response

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

No worries. If you have a reason to think your using coolant (milky oil etc), then its an easy call with your vin # to a dealer to see if those TSB's applied to your motor.

I've never seen this problem actually manifest in any of the performance vehicles I've encountered. Most coolant issues I see relate to overheating, air bubbles/steam line issues etc...If your heads have ever been off before, then there are a few other possibilities, but we're worrying about nothing if you don't have any reason to suspect usage in the first place.

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

This has been a known problem for years. It was a manufacturing defect. Google 'Castech heads' and you'll find out all about them and how to tell if your engine has them. If I recall correctly theyre the 862 heads.

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

706 and SOME 862's had this issue. Google it and you'll find a detailed thread on ls1tech. I checked my heads over to be sure, no Castech logo and no cracks.

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

Bravada, Envoy, Rainer, and Trailblazer were available with 5.3L engines.....

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

i've never seen a Bravada with a 5.3l, and there is even a specific reference to the fact that the Bravada was the only platform-vehicle on the GMT360 that DIDN'T get a v8 option at all.

The Blazer and Jimmy also don't apply to this list, as neither came with a v8 option at all, let alone an LS based one.

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

The TSB has been around since '06, Old news, But still freaks people out.
The FACT is a very low percentage of "Castech" heads crack, I have only seen 1 706 Castech head fail.

People like to make a mountain out of a mole hill....

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

I thought I had this problem of leaking cylinder heads on my 2003 5.3 and had read the GM TSB.

Most of the issue was the crappy steel freeze plugs that GM installed on the cylinder heads. Despite having changed the Dexcool regularly, the freeze plugs in the heads corroded and leaked.

To get the freeze plug out of the back of the head, it is less labor hours to pull the engine out of the truck than it is to pull the cylinder heads and change out the freeze plugs. What a PITA.

If you are building a LS motor and your heads check out ok, you should consider replacing the freeze plugs with good brass plugs before you install your engine

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

My 2004 LQ4 with 317 heads looses some coolant..But it has 355,000 miles.

Re: Coolant Loss 4.8 & 5.3 Vortec GM
 

140,000 on the bottom.....pressure check, grind, & fresh springs on an 862 casting, No issues, & I run green coolant in that mill.....it would be like a milk shake, in the oil..... no issues,longhorn :chevy: