04 gmc sierra coolant leak

[Omallyjenkins]

I have a 04 gmc sierra 1500 5.3 that I bought a month ago ( recently converted from ford owner after many problems that made me want to set it on fire) anyway after buying this truck I wound up with a cracked radiator. Now it being plastic could have happened after I bought the truck as the are ticking time bombs lol. I replaced it and everything seemed fine. Went on a trip back home and wound up with the thermostat getting stuck because it sucked the internal gasket in and locked it in place. So I replaced it in the auto store parking lot at 930 At night. I have no idea how long it had been stuck but from the gauge the truck never overheated. Now I am having a new issue I have a leak from the coolant system( I know big shocker seems to be a common theme with this truck) well after seeing the puddle under the truck I did my normal checks water pump thermos stat hoses. After finding them all good  I grabbed the trusty flashlight and did some more looking. I found the leak turns out it is coming from the passenger front head bottom corner right above the exhaust manifold. Now I have seen blow headgaskits before and mostly they are internal. What would gause it to leak from just that point not mixing in the oil and not blowing into coolant system. Is it a blow head gasket or warped head. Being my first gmc I don't know the common issues with these trucks. Oh one last thing I did notice a substantial drop in fuel millage for 17 on the highway to 12 on the highway. I am working on the road and I am limited on time and tools to fix this truck any help woulf be great

[CamGTP]

It would be worthwhile to grab a mirror and check the back side of the cylinder head. The heads have a freeze plug in the back instead of freeze plugs in the rear of the block. Possible the plug is leaking and showing the coolant on the back corner where you are looking.

[Omallyjenkins]

8 hours ago, CamGTP said:

It would be worthwhile to grab a mirror and check the back side of the cylinder head. The heads have a freeze plug in the back instead of freeze plugs in the rear of the block. Possible the plug is leaking and showing the coolant on the back corner where you are looking.

It's coming from the front corner lower left 

[dtnel78]

Look real closely at the water pump and make sure it's not blowing over or maybe vehicle leaning and causing it to leak that direction.

Go to a autoparts store and have them pressure test it for you.

IF it's the water pump spend the money and replace thermostat, fan clutch and all since you'll have it apart. The torque on the water pumps isn't very much so don't crank the thin seal ring down or it'll leak.

When you get back home flush, fill and make sure it's good to about -20. IF you were up North unless you are then I'd say -30 to -40 below 0. Make sure to use the recommended coolant as certain coolants will eat away at certain gaskets. In my 04 Tahoe it takes the Orange Coolant, Dex Cool if I recall correctly.

When I replace the water pump I did the fan clutch as well along with the serpentine belt, the AC clutch accessory belt, the accessory belt tensioner, the main serpentine belt tensioner, and any idler pulleys. The truck had 100000 miles on it and I had already replace the alternator so I just spent the $500 on parts and slap them all on as that's what a water pump would have easily cost at a dealership or at least $400 at a private shop.

Take care of the truck and it'll take care of you. Mine is just a little 4.8 Tahoe but for about seven years I was telling her 28 foot camper trailer with it which was about 4,800 lb empty weight and about 6,000 pounds loaded weight half full of water heading to the campground with all gear in it.

Insurance totaled the camper out after 7 years due to a water leak. I actually came out of that pretty good being that the trailer I got was a demo model so I only lost about $2,400 from what I paid for it but what I got for it off the insurance claim.

If you do want to pull in the upper intake by some chance go ahead and replace the knock sensors if you see that they don't have a bead of RTV silicone around the cover to create a damn to keep moisture out of the knock sensor hole.

GM has a TSB on that. If you search GM knock sensor TSB on the SUVs from early to late 2000's you'll come across it.

Also Google search GM pump rub and make sure your transfer case don't have a hole in it.

I would drop the oil anyways and refill it when you have time. It's easier to fill it using a pump bottle with a flexible tube on it versus trying to pour it in between the support braces and everything. If you do have a leak and have to replace the rear of the transfer case housing there's a company in Michigan that makes a fully new machined pump for the transfer case and you don't have to get that silly little clip and there anymore as it fills the whole transfer case empty space up.

The company name is Merchant Automotive. Here's the link for the kit which has got cheaper than when I had to fix mine. I didn't it myself and saved quite a but of $$$$$

IF you have the Auto Shift transfer case don't use the Auto button anymore as it wears the clutch pack out. When I have my transfer case out and the back cover pulled off and everything cleaned up along with the new parks and place ready to go back together I ran it by the transmission shop and had them check everything else over just in case there was something I wasn't aware of and they found the clutch pack was warned and put a new clutch pack in. The owner knows me well so right away he asked me why I've been using my Auto 4 wheel drive and I told him because it's easier and he said stop using it otherwise you'll put another clutch pack in it.

He said it's best to just use too high or 4 high then push the button when you need to change over on the pavement surfaces which makes sense.

Just thought I'd throw the few extra pointers out there and hope you don't mind as you never know what you bought into and if you're aware of a few things and you can slowly bring them up to your standard if you like to keep it in Tip-Top shape.

Here's the link to Merchant Automotive,


https://www.merchant-automotive.com/10001-Transfer-Case-Pump-Upgrade-Kit.aspx?utm_source=bronto&utm_medium=email&utm_term=Image+-+Transfer+Case+Pump+Upgrade

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[Gagliano7]

Also check the head steam ports. Been known to leak and can run down where you are describing.

[Omallyjenkins]

1 hour ago, Gagliano7 said:

Also check the head steam ports. Been known to leak and can run down where you are describing.

What do you mean steam port never heard of that. I know its not the water pump it will leak when the truck is off. Clean up the spot and it returns in less than a second

[dtnel78]

What do you mean steam port never heard of that. I know its not the water pump it will leak when the truck is off. Clean up the spot and it returns in less than a second

Water pumps leak when cold and will leak pretty quickly as well.

Find a parts house with loaner tool program and pressure test the cooling system. Have to start somewhere.

When mine was leaking I had driven across town went inside and visited with the insurance lady for 15 minutes and came back outside and I had a 30 ft long puddle of coolant running across their parking lot in the winter and like I said I'd only been in there 15 minutes.



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[Omallyjenkins]

Had the system pressurized and no leak I am at a loss now I know it was running from the front corner of the head but it held pressure so I have no idea

[Gagliano7]

16 hours ago, Omallyjenkins said:

What do you mean steam port never heard of that. I know its not the water pump it will leak when the truck is off. Clean up the spot and it returns in less than a second

Every ls motor has the steam ports. 2 on each heads the ones in the front are tied together with a small pipe between heads. If you look behind the alternator on the head down by the intake manifold you will see it.