Water pump & Coolant drain n change

Mattt · May 2, 2018

I'm going to be replacing a water pump soon here on an 04 Tahoe. I may change to a different coolant instead of putting Dexcool back in. Does the 5.3 block have drain plugs like previous generation SBC and BBC's? I'd like to drain the block during the swap, even if I don't change coolant type. 266k miles could have built up crap in the block water jackets. Thanks in advance.

Supreme Pizza · May 2, 2018

Here is what I do:

Pull the thermostat out and put the housing back on. Then remove the upper radiator hose connection. Tape then garden hose to the radiator hose, and turn the hose on full blast. Start the engine and let it run until the fluid comes out clear for about 30 seconds. Now remove the garden hose, and put a large funnel on the hose, and prop it upright. Then pour gallon after gallon of distilled water into the funnel while running the engine. Then open the petcock on the radiator and let it drain. Replace the thermostat, close the petcock, put the radiator hose back on, and refill the radiator with 100% Dexcool (not the 50/50 premix). Leave the radiator fill cap off, and start the engine. Run the engine from idle to about 3k and then back to idle several times, for about 15 minutes. This will bleed the system. Replace cap. Drive for a bit, let it cool and re-check fluid level. Check to make sure the system is holding pressure (feel the upper radiator hose - under pressure?). Check the fluid level each morning for a few days.

Mattt · May 2, 2018

Thank you for the reply. I will take the advice. Anyone know if there are block drain plugs anywhere?

Why would you use 100% Dexcool instead of the 50/50 recommended by the factory? I believe water cools/sheds heat better than coolant, from what I've read.

txab · May 2, 2018

Using the method starman describes, their will be some water still in the system. Adding 100% coolant until you get to the 50% required coolant amount. Then topping off with distilled water until full. If you go with 50/50, your mix ratio will be off as a little less than half the total system capacity will be retained in the block as pure water.

Their is a block heater port on the drivers side you can remove if you wish

Mattt · May 2, 2018

Thanks txab. Is that block heater port a hex head, large diameter, small diameter, towards the front or back? I was thinking flush allen head plug like old generation blocks had to be able to drain both sides of the block jacketing. So the 5.3 block does not have something comparable?

I would mix coolant and distilled water at a 50/50 ratio, then dump it in the reservoir. How I've done it in the past is to mix 1 gal of coolant with 1 gal of distilled water yielding 2 gallons, then repeat procedure until full.

Anyone have opinions on not re-filling with Dexcool and moving to a regular green long life coolant? I know from reading here and elsewhere that back when Dexcool first came out it was corrosive to many different surfaces. Is that still the case? I can go back with Dexcool or any other coolant. Local radiator shop said in his opinion that it doesn't matter much any more because all long life coolants are pretty much the same.

Lastly, I believe my coolant/water loss is from the water pump. I have staining near & below the weep hole where the shaft seal is on the water pump. The original pump in my 04 Tahoe has the side weep hole that can be seen from below the vehicle. The replacement pump I have to go in has the weep hole behind the pulley in the center so it will be much less visible if/when this pump springs a leak, bummer about the weep hole being moved to a spot that it can't be seen.

I've looked at the existing pump weep hole both when running and with the engine off but have never seen any moisture present.

Is there a way to determine if I am losing coolant/water elsewhere besides the water pump......think like heads or head gaskets? I thought there is some sort of test that can done to either the coolant or the oil for residual traces of the other fluid? I'm not certain or saying for sure that I'm losing coolant elsewhere, but I figured it's a good time to check.

Thanks for all the info and pointers in advance.

Supreme Pizza · May 2, 2018

I would stick with OEM coolant, or you could go to a universal type - as opposed to green.

As for your coolant leak, I would put a pressure tester on the coolant cap, and pump up the pressure. If you lose pressure with no drips, you have a problem with your head gasket, trans cooler, or something like that. If you get drips, just follow them to the problem. Its unlikely that you have 2 leaks. I would definitly not change the water pump until you actually see coolant leaking out of of it.

This is not price shopped, it just the first one that came up. Look for a better price, maybe on eBay. Also, your local parts store will loan you one for free.

https://www.amazon.com/8milelake-Radiator-Pressure-Universal-Cooling/dp/B075S1TCQZ/ref=sr_1_10?s=automotive&ie=UTF8&qid=1525298790&sr=1-10&keywords=radiator+pressure+tester

Supreme Pizza · May 2, 2018

Here is another option, but its has it has its disadvantages.

Mattt · May 2, 2018

38 minutes ago, starman8tdc said:

I would stick with OEM coolant, or you could go to a universal type - as opposed to green.

As for your coolant leak, I would put a pressure tester on the coolant cap, and pump up the pressure. If you lose pressure with no drips, you have a problem with your head gasket, trans cooler, or something like that. If you get drips, just follow them to the problem. Its unlikely that you have 2 leaks. I would definitly not change the water pump until you actually see coolant leaking out of of it.

This is not price shopped, it just the first one that came up. Look for a better price, maybe on eBay. Also, your local parts store will loan you one for free.

https://www.amazon.com/8milelake-Radiator-Pressure-Universal-Cooling/dp/B075S1TCQZ/ref=sr_1_10?s=automotive&ie=UTF8&qid=1525298790&sr=1-10&keywords=radiator+pressure+tester

Thank you for all the suggestions. The universal type, all applications coolant I've seen recently is green. I don't even know if the old style green is still being sold.

The water pump is definitely leaking. Dealer has brought it up to me any time I've had it in there for other service.

I have rented one of those in the past from O'Reilly's locally. That is a good idea. Hopefully they have an adapter to work on the reservoir.

The one I will definitely pass on is Bar's Leaks.

Still kind of surprised they omitted the block drains that every other engine I've seen had somewhere????

Supreme Pizza · May 2, 2018

Your not a fan of stop leak, eh? That makes 233,627,488 of us.

Supreme Pizza · May 2, 2018

You can buy some time on the water pump by putting a glob of JB weld or Permatex Gasket maker over the weep hole on your pump. Not a long term solution obviously, but its an old trick that shady used car salesman do. It stops the leak for a while. Just make sure you swap it out before the engine fan takes a bite out of your radiator. (assuming you have a mechanical fan).

Mattt · May 3, 2018

Thanks, but gonna change it soon here, like in the next week. I've been putting it off for about 10-12 months, so it's time now that I have the pump and t-stat, water neck. No used car salesman trickery necessary.

Mattt · May 8, 2018

Uh oh....looks like it might have the Castech cracked head going on too, in addition to a leaky water pump. I haven't pulled the oil fill cap or looked down the tube much recently since my local dealer has an oil change deal that makes dealer oil changes a no brainer. 3 oil changes for $60 if you pay for all 3 up front. Pretty bummed the GMC dealer never reported seeing this.

This 5.3 has 862 heads, which from what I've read the crack is more typically on 706 heads, but I did find a few instances online of 862's with the problem. The yellow colored spooge down in the tube is kind of gel like. I was able to reach it with my finger. It is yellow in color, not the normal tan, chocolate milk shake color that I've seen in prior water intrusions with oil. Is that what you see looking at this picture of the oil fill tube.....a cracked cylinder head(s) and water residue in the oil?

Supreme Pizza · May 8, 2018

I would say that you might have a problem. I wound not jump to any conclusions yet. I see actual drops of water under the oil fill cap on Suburban 5.3's fairly often. Its just the condensation built up from heat cycling the engine. When you drop the oil or pull out the dipstick, how does it look?

Mattt · May 8, 2018

When I've changed the oil myself, it did not look milk shake style. There is no indication of oil/water mix on the dipstick. I know most people pull a valve cover to look at the heads for cracking and oil/water sludge. With the water usage recently, and the lack of visible dribble from the water pump weep hole, the head crack thing has been on my mind, which is why I looked down the oil fill tube. The substance that came out on my finger was definitely oil/water mix. The color was kinda weird though.

txab · May 8, 2018

Pull the cover(s) and/or test the the oil for the presence of coolant. You could simply being seeing signs of condensation. How much coolant are you adding and how often? A WP can loose quite a bit without it actually pouring out. If it leaks while hot it will evaporate. You mentioned seeing signs of leakage at the WP.