2004 5.3L Silverado Losing Coolant

endo.1 · September 15, 2010

I have the same problems as outlined above and have received EXCELLENT help from this forum, I had to register and say thanks in advance. I'll be pulling the valve covers tonight, no question.

In the meantime, just doing some research, if I were to buy 862 heads, they'd be direct bolt-on replacements correct? From what I've found so far, they will, I just want to confirm. I don't have $2000 for Trick Flow heads, and I've found several low mileage 862 heads for $200.

Thanks again, I'm very impressed with how thorough this thread has been!

endo.1 · September 15, 2010

Just found these guys through a link on another forum, looks like a damn good possibility!

http://www.shop.headsonly.com/CHEVY-SILVER...ILVERADO-53.htm

tiggertim12 · October 2, 2010

I have a 2005 silverado 4x4 w/5.3 45k with the same problem. I took it to the Chevy dealer and pointed out the bulletin and described my issue. They did all the necessary test to rule everything else out. They couldnt find anything. However they did say if there is a problem with the head it will get worse. So I/they are going to take the wait and see approach. It appears to be holding coolant for now with no sign of leaks or exhaust blow by.

endo.1 · October 12, 2010

Got the truck back together on Friday, did an oil change and coolant flush, new spark plugs...good to go. The new heads from headsonly.com are awesome and other than being time consuming, the job wasn't all that bad. Drove almost 400km this weekend to go camping and did another oil change tonight. Ran great!

Jhelmeste · December 2, 2010

Unfortunatly I own the same truck as you do, a 2004 GMC SIERRA Z71 WITH THE 5.3L ENGINE.

Recently, I discover gradual coolant loss over time with NO evidence of any external leaks and no changes in driveability and performance. Even the oil looked perfectly normal... After a little digging, this is what I found:

My truck is affected by GENERAL MOTORS SERVICE BULLETIN ##06-06-01-019B: Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found - (Jun 12, 2007)

I inspected the cylinder heads and sure enough found the tell a tale signs that are indicative of "porosity cracks" in the cylinder heads in a very specific area. I found the cracks in BOTH of the heads in the same location!

I also noted the heavy "butter scotch" sludge that coated the underside of both of my valve covers. I can't help but wonder what damage this has caused my engine and most certainly shortened its operating life.

Currently I am approaching GENERAL MOTORS OF CANADA to urge them the carry out the repair at their expence as this is a blatantly obvious defect in craftsmanship on their part.

I may be gathering names and information of people affected to present to GM and request arbitration on this specific issue if they fail to remedy the problem.

Just look at the attached photo's!!!

1- CASTECH casting mark

2- Porosity crack easily visible with dye added to the coolant3

3-"Butter scotch" sludge unside of valve cover

[email protected] · December 2, 2010

Jeez your heads are dirty, most the ls engines I've seen apart still were very clean inside, no sludge AT ALL. I guess that's what water in the oil does under heat.

December 3, 2010

Just found these guys through a link on another forum, looks like a damn good possibility!

http://www.shop.headsonly.com/CHEVY-SILVER...ILVERADO-53.htm

So since they require a core return and their "heads come from GMC and Chevrolet trucks and SUV's." how do you know you are not getting another set of crappy Castec heads?

December 3, 2010

3-"Butter scotch" sludge unside of valve cover

I had a slight leak from my water pump and replaced it a couple of months ago. Still loosing some coolant but MUCH MUCH slower. I just noticed that exact color of "butterscotch" on my oil fill cap the last time I checked.

garynmelinda · December 6, 2010

I have been losing coolant for about 25-30 thousand miles now. At first I attributed it to the water pump or gasket going bad. My brother n others I know have had this problem in the past and i was putting it off because of laziness. I then purchased a "All Data DIY" membership for service info before replacing my pump. After reading the service bulletin about the porous heads, i got nervous. My truck fouled a spark plug on the #4 cylinder due to oil getting in. I decided to pop the valve cover n take a look after i went by the oil change place n they told my oil was so badly gummed up, they had never seen anything like it. I purchased this truck new and have 110,000 miles and serviced it regularly and knew something was wrong. I saw more sludge than ever before under my valve cover than on trucks i've had in the past with 3 times this mileage. I saw a nice clean area just as described in the SB. I pressured up the coolant system and watched the water start seeping out exactly where they described it. UNBELIEVABLE!!! And everyone is telling me GM says the resposibility is all on the owner. Im very discusted with GM to say the least.

97Silverado1500 · December 11, 2010

I'm new to this forum & just read this topic. I have had the same problems, as described all through this thread, on my 97 Silverado 1500. Engine never warmed up over 110 degrees & I was losing coolant but couldn't find a leak. I went to Chevy & bought a thermostat, some flush, coolant, & a radiator cap. I put the flush in, topped it off with water, & put my old radiator cap on & waited for the 10 minute run through of the flush. While I was waiting I took the hose to the reservoir off at the radiator & flushed it out as well. I left the reservoir hose off from the radiator while I was waiting & I noticed water shooting out of the nipple at the radiator & then it would stop for a few seconds & then do it again. All the water was going into the reservoir because of a weak spring in the cap. It would fill the reservoir & overflow through the overflow tube on the reservoir. It probably does this while you are driving & the water pump is pumping at it's max. So I took the old cap off & put the new one on & it never did it again. I finished the flush & rinsed it out of the block & radiator. I replaced my thermostat, topped it off with 70% coolant & 30% water, put the new cap on, cranked it up to check for leaks, & to let it warm up again. No leaks...whoohoo. I took it on a test ride & the temp went up to the normal range. My old thermostat was sticking open never letting the engine reach operating temps. Both problems solved for about 60 bucks. To sum it all up, if you lose coolant & can't find a leak...replace the radiator cap. If your engine runs too cold...replace the sticking thermostat. The radiator cap is cheap enough & easy enough to do before tearing your heads apart. If it doesn't fix the problem then your problem is more serious & is probably in the head. My cap was 21 bucks from the dealership... Hope this helps & good luck to anyone having this same problem...

jmilana · February 12, 2011

I would sure like to know the answer to this question!

Just found these guys through a link on another forum, looks like a damn good possibility!

http://www.shop.headsonly.com/CHEVY-SILVER...ILVERADO-53.htm

So since they require a core return and their "heads come from GMC and Chevrolet trucks and SUV's." how do you know you are not getting another set of crappy Castec heads?

jmilana · February 14, 2011

OK, to answer my own question, I called emailed headsonly.com and recieved this reply: We have been repairing them for a long time with no comebacks due to the problem you are

referring to. We weld the weak parts of the casting."

rdnkcpa · February 15, 2011

OK, to answer my own question, I called emailed headsonly.com and recieved this reply: We have been repairing them for a long time with no comebacks due to the problem you are
referring to. We weld the weak parts of the casting."

It may work, but I would not be too confident in the longevity. i bought a new set of bare heads and had my valves reground and transferred over for $780.00. That price included pressure testing of the old heads.

I'm hopefully going to get started on putting them on this weekend.

jmilana · February 15, 2011

So where did you get the bare heads?

jmilana · February 17, 2011

Talked to a local guy today that has done several. He said he has seen defective heads pass a pressure test. He has also experienced high mileage engines-75,000+ become oil burners after installing new heads. Short of getting rid of the truck, he recomends a new engine with a 100.000 mile warranty for not much more money.