02' Silverado slow coolant loss 4.8L, 1/2 ton, 2WD

[Eagle70ss]

Hey y'all I have a slow coolant leak with no visible signs of leakage. I would say it's about a 1/3 gallon every six months. There's nothing leaking onto the ground or anything coming out of a hose that I can find.

I know there was a problem with certain head castings developing porosity and leaking internally. It says in the TSB that a very low percent used these troubled head castings. Does anyone know any exact numbers? 1%, 5%, 10%. "Very Low" can be a loose term. The engine oil looks clean and I use an external tranny cooler so it doesn't run through the radiator(tranny cooler holes are capped).

I've heard intake gaskets and water pump leaks are my best places to start looking. Anyone know of any test I can do to verify problems before I tear the engine to pieces?

Thanks

[Scrapper]

do you have any kind of miss when driving or hear it miss when just idleing? have you got a pressure tester or do you see any kind of green on radiator or hoses? i would pull the plugs and do a compression test to see if you have a leak on your heads might even be a small hole in heater core or like you say waterpump but look for a nasty green on every hose you can see and radiator...good luck....

[Eagle70ss]

Originally Posted by Scrapper

do you have any kind of miss when driving or hear it miss when just idleing? have you got a pressure tester or do you see any kind of green on radiator or hoses? i would pull the plugs and do a compression test to see if you have a leak on your heads might even be a small hole in heater core or like you say waterpump but look for a nasty green on every hose you can see and radiator...good luck....

I don't notice any kind of miss at idle or any other time. I can't smell any coolant in the cab. Going to loan out a pressure tester at the zone and do a cold pressure test to see if I can see a leak. I'll post back with updates.

[jdmccright]

'96 and up uses Dex-Cool...it'll be orange not green. If there are no visible leaks, and not using the integral tranny fluid cooler in the radiator, the only two ways out are the oil and the intake manifold. You can have the oil tested for antifreeze contamination and a leakdown test might reveal if you have a problem casting. Sometimes you can even smell the sweetness of the coolant in the exhaust. Finally, I'd check the radiator cap. You might be losing it due to evaporation. Hope this helps!

[isie]

The gaskets for the water pump leak, and the anti freeze drips down the engine and burns off before being seen. with the truck running slide under neath with a flashlight and look at where the pump mates to the block. simple fix, and I always flush the anti freeze at this time and replace with new dexcool

[j cAT]

Originally Posted by Eagle70ss

I don't notice any kind of miss at idle or any other time. I can't smell any coolant in the cab. Going to loan out a pressure tester at the zone and do a cold pressure test to see if I can see a leak. I'll post back with updates.

I doubt the pressure tester will reveal anything...1/3 of a gallon[1.5quarts] in 6months is not a lot of coolant...

I would guess that the water pump seal is leaking at times when the engine is running....try to check after running engine on cold start after a 5minute warm up..place your finger at the water pump weep hole for coolant/residue...

if the block does have a corrosion problem lack of proper coolant of sufficient quantiy this leakage usually grows at a rapid rate...

use distilled water ...

[Eagle70ss]

jCat,

It looks like you were correct about the water pump gaskets. I looked under the WP gasket location on the pass. side and I saw it was wet. There's only a small space to look through, but I saw some liquid shimmering. So I figured I would give it a shot and change them. It sounds like it's only a matter of time before they start to leak anyways.


This is what the passenger side inlets looked like. The bolts were all caked up with gunk and corroded from coolant leaking into the WP mounting holes. So I cleaned all gasket surfaces and bolts down to the bare metal and applied the new gaskets. Flushed the entire system out and went back with new Dexcool and distilled water. All seems well so far. No wet spot under the gasket points anymore.


So hopefully problem solved.

FYI..The GM dealer was cheaper on the gaskets than Autozone and Oreillys. I didn't check Pep girls.
6.99 each at the dealer(AC Delco) and 7.99 for Felpro aftermarket. DFW area.

[j cAT]

[quote=Eagle70ss]jCat,

It looks like you were correct about the water pump gaskets. I looked under the WP gasket location on the pass. side and I saw it was wet. There's only a small space to look through, but I saw some liquid shimmering. So I figured I would give it a shot and change them. It sounds like it's only a matter of time before they start to leak anyways. [quote]

thanks for all that and the pictures...yes the coolant is very important here in these engines...not like when they where all cast iron...

corrosion is the killer...and its very hard to completely remove all the coolant when the time comes to service this.. good luck..

[Eagle70ss]

Here's a guide to change these gaskets( 2 in total). It's just the way I did it and it worked out pretty well.

1. Drain coolant by opening drain cock on drivers side on the bottom of the radiator. Mine came with a hose attached so you can guide the coolant into the container. Retighten the drain cock after coolant drains before you forget.

2. Remove air intake hose and baffle. Loosen clamp at the air filter box and the clamp at the throttle body. I used a 5/16 socket for all clamps. It's better than jacking with a slot screwdriver slipping out all the time(I have the aftermarket worm-gear clamp type. Then the whole hose assembly will come off. There are some clips to unfasten too. I think two.

3.Loosen clamp for the upper radiator hose and remove hose from water pump side. I left the other side attached. Just bend it out of the way. Leave all other WP hoses attached. There a small vent hose running from the radiator to intake or WP. Unhook from the intake side and get it out of the way.

4. Remove main drive belt by using a 15mm socket or wrench to adjust tensioner so that the belt loosens. Remove the belt and set it to the side. This should be all the prep you need before removing pump. There should be a good open space for you to work.

5. There are 6 water pump bolts, three on each side. My bolts were 10mm head size. I used a ratchet, small extension, and a 10mm short socket. There is not much room between fan and the bolts. Remove all six bolts and scoot pump away from the block to remove gaskets(2). Clean both water pump surface and block surface to ensure gasket will seal well. I used some scotchbrite pads and it was sufficient to clean the surfaces.

6. Install new gaskets by the method of your choosing. Installation is reverse of removal. I flushed my cooling system thoroughly and put new dexcool and distilled water.


This should get you pretty close. If anyone can add anything to procedure, feel free to do so.

[isie]

I also use the coolant drains in the engine block to make sure that i got all the old dexcool out. I also have friends who didnt and they are still fine with there dexcool, aslong as your cooling system isnt in bad shape and you only use dexcool its not as bad as some would believe. and only use distilled water no minerals in it, I always use pre mix as I have a well.

[abhicar]

Thanks, The information is very useful.

[j cAT]

Originally Posted by isie

I also use the coolant drains in the engine block to make sure that i got all the old dexcool out. I also have friends who didnt and they are still fine with there dexcool, aslong as your cooling system isnt in bad shape and you only use dexcool its not as bad as some would believe. and only use distilled water no minerals in it, I always use pre mix as I have a well.

exactly what tool and technic did you use to remove the engine drain plugs on these engines ? I have tried and could not remove them..also on the passenger side you must remove the starter motor.

[isie]

you need a 17mm hex head socket, snapon part #sam17e wasnt hard yes had to remove the starter. In my opinion it is worth the effort.

[isie]

I forgot if it has a block heater then you need a box end wrench or deep socket, I dont rember off the top of my head what size, only had one with the block heater.

[j cAT]

Originally Posted by isie

I forgot if it has a block heater then you need a box end wrench or deep socket, I dont rember off the top of my head what size, only had one with the block heater.

I used a 17mm allen socket 1/2in drive with a pipe 2 ft long for leverage...I stopped because I felt I was gonna break something...did you use an air gun ,heat ,how did you get it to break loose...?

no block heaters..