2004 5.3L Silverado Losing Coolant

99xjsport06 · October 24, 2006

Howdy fellas.

First off let me say ya'll got a nice forum here. I've recently found a problem with my step dad's 2004 Silverado, with the 5.3L, right at 83,000 miles....bought brand new. While going to dinner two weeks ago, it began to over heat. The temp. guage would get to about 230-240, hang there for a minute or so, and then settle right back down to 210. It would then stay at 210 for a while, and slowly begin to creep back up to 230-240....it never got to the red zone, which is a good thing. All this was happening while driving down the road. Sitting at a light or in traffic, it would creep up a little bit, but only to about 220 or so.

Once we got out of the restaurant and the engine had about 3 hours to cool back down (as it was a chilly night), I checked the level, and sure enough it was low...practically empty. About one month prior to this when I changed the oil on his truck, I noticed the coolant level was low, but not this low. I topped it off and didn't think much of it....figured all the miles on it, maybe it just got low over time.....until that night at the restaurant.

We managed to get it back home (about 20 miles away) that night with it still doing the same thing. First thing the next morning, I once again filled it back up (taking an entire gallon to bring it back up to full), and the overheating has stopped. Problem is, the level is significantly lower than it was 2 weeks (will be 3 weeks this weekend) ago. It is not leaking on the outside, so it's definitely something internal.

First thing I checked was the oil, and it looks fine and does not smell of coolant, although I'm not totally ruling out the possibility that there is a small amount getting inside the crank case. He told me that one day last week he fired it up in the garage to leave for work in the morning and he said it blew out a pig puff of white smoke, but ran just fine (which is making me lean away from a Head Gasket problem) and cleared up pretty quickly. Then, this past Friday morning, he went to run some errands and noticed the valve's tapping very loudly when he first fired it up, but that also cleared up pretty quickly.

My question to you all is, does this sound like an intake gasket issue? From talking with my dad who has been mechanic for almost 40 years, he's had to put a lot of intake gaskets on GM vehicles (just did one last week on a mommy van as a matter of fact) and says they're pretty common to go out.

Again this truck has almost 83,000 miles on it, and they're pretty much all highway miles (he does at least 70 miles a day round trip for work). He bought it brand new and takes pretty good care of it.

I've got zero experience with Chevy trucks....I'm a Jeep guy and my knowledge is mainly in Cherokee's and Liberty's, as well as somewhat on Wranglers, so I turn to you all for advice. I'm no stranger to forums, and I did use that handy dandy search feature, but did not really come up with much of what I was looking for.

So if anybody has got any advice to throw my way, by all means throw it. And I apologize if this is in the wrong thread, so feel free to move it if need be.

Oh and once again the specs: 04 Silverado, 5.3L, Automatic, 4x4 (not that it matters), 83K.

And yes, I did make sure to put the orange Dex Cool coolant in it. I've converted my Cherokee over to the orange stuff and the Liberty being a newer vehicle came with it from the factory, so I've got plenty of it in my garage.

Thanks for your help guys. This is the first issue he's had with this truck.

1999 Tahoe 4x4 · October 24, 2006

Tere is a POSSIBILITY that your leak is not as big as you suspect as you MIGHT HAVE NOT topped off your system properly.

As far as I know on the 5.3 the coolant does not circulate through the intake any more. So that would eliminate an intake manifold gasket leak.

You may have many areas where a leak can occur. So therefore at this point what I would do is to fisrt PROPERLY fill up and bleed the cooling system. (Just in case that you don't know the proper procedure send some note again: if not me, I'm sure there will be many guys who respond how to.) Then I would let the engine completely cool down and perfom a leak check with a pressure tester. Note the pressure drop and start looking for leaks.

99xjsport06 · October 25, 2006

Thanks for the reply.

I topped it off properly. I took the cap off, filled it all the way up, cut the engine on and let it pull some into the radiator, then while the engine was running i topped it off once again. Drove it around all day with no problems. Checked it once more the following morning and the level was still where I had it....so i'm pretty sure no air got in the system while I was filling it back up. This is the method i've used every time I've done a coolant flush on my Jeep and other vehicles and haven't had any problems.

Interesting about it not running through the intake anymore....I was not aware of that.

A pressure test is definitely in order....just gotta find the time to get it done.

Thanks again, and any more suggestions guys keep em commin!

Koinz · October 25, 2006

I used to use my compression tester adapter to apply compressed air to each cylinder with the valves closed on that cylinder and watch for bubbles coming up through the radiator cap.

Donot do this with the cap on. It will blow-out your radiator.

Also, Pull the plugs and look for one that might be much cleaner than the rest. If it's a head gasket, the cylinder that is leaking will run hotter than the rest and basically steam clean them.

Hope you find the problem.

99xjsport06 · October 26, 2006

I was planning on checking the plugs this weekend.....i'm making a nice little list of things to check to hopefully narrow down the problem. I didn't think about blowing compressed air into the cylinders and watching for bubbles.....I like that Idea.

Keep the advice coming.....nothing can hurt!

I'd still like to find out if this is a common problem among these things or just a fluke in his. d**n thing has been rock solid since the day he got it....even towed my jeep back from the beach 5+ hours when I was having problems with it (long story...lol).

1999 Tahoe 4x4 · October 26, 2006

Look, I don't want to blow down the "Bubbles" idea of Koinz. But I really recommend to get real pressure tester. Should not be more than $70.- and you'll be able to use it for a long time. It's good practice to pressure test the system once a year anyways, just to know what you deal with. Plus this way (pressure tester method) you'll know for sure if and you'll know for sure where. After all a leak could be in the radiator, heater just to name a few and these would not be able to be diagnosed with the buble method.

Koinz · October 26, 2006

That is an excellent point and should be done first.

I have had vehicles where the leak is so small that a pressure tested couldn't find them so we would revert to the Cylinder leak test.

If it running hotter than normal it's probably a head gasket.

99xjsport06 · October 26, 2006

We're definitely pressure testing it...just a matter of when we can find time....I'll be going back home from school tomorrow and messing with it all weekend to see if I can't track this down.

As far as running hot, It was only doing that because it had almost zero coolant in it.

Thanks a ton for the help guys. Gotta love these online forums....save a hell of a lot of time for the do it yourself-er. And I appreciate not having my question shot down by a bunch of know it all people...see alot of that on a few Jeep boards that I frequent alot and it really is a shame.

I'll post back once I do some tests on it and get some results. Really hoping it's not the head gasket.

I still haven't ruled out the possibility of a small leak in say one of the radiator hoses or somewhere else...that only pops up when the system is under pressure and it so small it evaporates or burns off as soon as it comes out.

So much to do on it this weekend.

99xjsport06 · October 30, 2006

Update:

Messed with the truck today and was unable to find a problem. Coolant bottle had 50% of normal ammount in it. So it looks like the leak has slowed down, but is still there none the less. Immediately upon opening the hood after driving about 100 miles you could smell hot coolant. I still cannot for the life of me find where it's leaking from. I've pretty much ruled out the intake as i've read several places (including a response in here) that state that it doesn't run through the intake on this engine, and upon closer inspection today it looks as if that is true.

The transmission fluid looked just fine. The oil concerned me a little bit. It looked for the most part OK, but it was more of a grey color than black.

While on the topic of oil, it was time to change it today anyways. I switched it over to Mobil 1 Synthetic on this change and it has, like i expected, quieted down the engine a bit. The interesting thing is I only got 5 quarts out of it, rather than the expected 6. This is the 2nd time I've changed the oil on this truck, and the last time I did get 6 back. On this previous oil the engine did get very hot from over heating, but i'm having a hard time believing that because of that it would burn up a quart of oil.

As far as the coolant loss goes, i'm now leaning towards a head gasket issue, but I am unsure as to how to go about testing it. I didn't get to pressure test it as my dad's pressure testing kit was slightly too small for the size of the opening on the bottle.

Any suggestions?

Thanks again guys.

99xjsport06 · November 4, 2006

Another Update:

All went well with the truck over the past week. As expected, no more tapping since switching to synthetic, and coolant loss appeared to be minimal.

However this morning, after the truck sat outside all night where temps. got down to the upper 20's, and he got in the truck to go to the store. The truck started just fine but upon start up it blew out a TON of blue smoke. Combining this with the missing quart of oil from the oil change last weekend, it appears as if there is a definite oil leak somewhere.

The fact that it only burned it upon start up and quickly cleared up is leading me to think that it's the valve stem seals? This would be easy to replace if we end up taking everything apart to put a new head gasket on it.

Are we the only ones who have experienced these issues or is this pretty common amongst the 5.3?

99xjsport06 · December 15, 2006

Just another update to anybody who gives a darn anymore or anybody who might stumble upon this thread in the future....

Oil burning and coolant consumption continue....along with LOUD valve tapping on occasion. The valve tapping almost sounds as if a lifter is having a hard time getting pumped up....but it doesn't do this very often.

As far as oil consumption/burning and coolant consumption.....i'm absolutely stumped. The oil burning happens almost every morning on a cold start up, and only happens until the truck has burned through exactly one quart of oil. Once it has done that, the burning upon start up goes away, and the level stays at 5 quarts. If I fill it back up to 6, the smoke show starts almost with in the next day, if not the 2nd day after.

For the coolant, i still have NO idea where it's going. I can smell it when I open the hood and the engine is hot...but I see no signs of leaks, cracked hoses, crack radiator....nothing. I've even left the fully warmed engine running and had a couple of people go over it with me (figured 6 eyes were better than 2) and none of us could see any signs of a leak that would only occur under pressure.

If anybody has any suggestions at all, i'm open.

Other than these issues like I said, the truck runs great and he's not had one mechanical issue with it in the 2 years and a ton of miles he's racked up.

1999 Tahoe 4x4 · December 28, 2006

I'm not trying to be a smartass but my 1999 5.7 uses 5 quarts of oil and I belive your truck is supposed to use 5 quarts of oil as well, not 6. You should definately check on that. If so that might explain why it burns that extra quart that quickly.

As far as coolant leak. You really HAVE TO get the leak tester. Trust me your money will be spent well because it WILL help you find your leak. You have to use it on a cold engine. Pump it up 15-20 psi max and wait, wait, wait. You will it will loose pressure and you will see spots the where the engine starts to sweat/cry. Check for leaks between the engine and firewall as well.

jwhjr · December 28, 2006

I'm not trying to be a smartass but my 1999 5.7 uses 5 quarts of oil and I belive your truck is supposed to use 5 quarts of oil as well, not 6. You should definately check on that. If so that might explain why it burns that extra quart that quickly.

5.3 uses 6 qts.