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coolant loss + gurgling

marzahld

SM 2022
PM 2018
SM 2015
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Apr 11, 2005
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uh oh.  In the last month or so I'm losing about 1 qt of coolant a week now.  Nothing under the truck after parking.  I changed the oil after refilling 1/2 gallon or so of coolant.  The oil was black and looked normal.  I'm about to take the skid plates off for a closer inspection.      The fluid in the expansion tank looks like clean dexcool.

I changed the water pump 2 years ago so I doubt this is leaking again.    I'm also hearing some gurgling from the expansion tank when I first apply acceleration after stopping at a red light. 
Anyone want to take a guess where my coolant is going? 
 
Head gasket ???

Any white smoke at startup.
 
marzahld said:
... I changed the water pump 2 years ago so I doubt this is leaking again. ...

Don't totally discount a water pump.

I had a new one go bad on our CTS within a month of installation.

The next replacement pump has been fine for over two years now.

Take a close look in the area of the weep hole behind the pulley.

A leak there often does not leave a puddle until right before total pump seal failure.

The water pump can leak tiny amounts for a long time and not leave much of a trace.

Worth a close look.

Doesn't cost you anything.
 
>Don't totally discount a water pump.
>I had a new one go bad on our CTS within a month of installation.

Winner, winner!  I can't believe it...  I just changed it ~2 years ago due to weep hole leak which I assume indicates internal failure to seal.  The first one was original, I replaced it with a Bosch 99169 in August '14.    Now the weep hole once again is black with small drops of fluid in random spots around the area.    Amazingly, no fluid had collected on the skid plate.  One would think if you were losing an entire quart per week, there would be a big puddle there.  but it kind of ran out on the axle and I guess the air movement down there while driving made sure nothing pooled up. 

Can someone recommend which brand water pump I should try next?

 
If you are going through a quart a week I would certainly think it would accumulate on the skid plate or at the very least leave a stain where dirt would collect.  I would have it checked for the rear intake manifold gasket leak.  Any good garage would simply add a florescent dye to the coolant and let it run a while, then with the lights off check around the engine with a black light.  The dye additive will glow showing them exactly where the leak is, at a much cheaper price than throwing another water pump on it if that is not the leak, especially when you say the weep hole is only a little black from dirt sticking to the area due to seepage.  If a quart a week was leaking out that hole, dirt wouldn't have a chance to cling IMO.
 
I would try a AC Delco pump, new not rebuilt.
 
>If you are going through a quart a week I would certainly think it would accumulate on the skid plate

This bothers me too..  no accumulation on the skid plate but the front differential shows signs of a fresh leak from above and dirt accumulation.  It would be good to verify that this is dexcool covering the diff and not oil..  I may add the leak additive  and check this out to be sure.  Although, maybe a wipe with a paper towel can tell me that.    Now that I think about it, I cannot recall it accumulating on the skid plate the last time it leaked either.  So if I believe the water pump is leaking a qt/week, the theory is leaks when moving and collects on the front diff, runs down, and is blown away while driving.

I know the pump has to be leaking at least some since there are visible drops of dexcool around the area of the waterpump and dirt around the weep hole.

If rear intake was leaking, wouldn't there be other symptoms or possible codes thrown?  dex-cool in the overflow tank doesn't show any contamination either.
 
I'm curious when you changed the pump the first time, how did you get the air out of the engine.
 
>I'm curious when you changed the pump the first time, how did you get the air out of the engine.

I didn't.  I'm pretty certain I read that its not necessary to do anything.  It works its way out on its own through the expansion tank (which is not air tight due to the overflow tube).  I just topped off again after driving it.  It has been problem free for 2 years after the initial change until now.  Hopefully I just had some bad luck with the replacement pump being sub-par--  also I see that the bosch 99169 is no longer for sale...  hmm...
I've normally had good luck with their stuff. 

 
Check the front of your passenger head for a number. You should see either a 706 or 862.

If you see a 706 then you MAY want to pop off the valve covers and check for signs of coolant.
These heads are known to have issues around the bolt holes cracking.

Seems to be a common issue with our trucks...

http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,150622.0.html



 
Water pumps tend to leak way more when they are spinning so the puddle you left would have been moer likley a trail down the road and a wet engine
 
I have not seen anything  about the 243 head cracking, but a few of them had the rocker mount pulled out. So yes you are good with them.
 
Well, I'm ordering a delco 252-845 to replace the bosch this time.    I attached a pic of the weep hole on the bosch.  you can also see a drop of coolant on a nearby bolt below it.     As to whether an entire qt per week could be coming out of that hole, I don't know, but it seems logical to repair the leak before going further.
 

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I replaced the bosch water pump with an ac delco this weekend.  I liked the delco kit better because it came with the fiber gasket as well as the water pump gaskets.  It also came with the o-ring gasket for the older style 1-piece t-stat for those that are still using that.    Last time I had to use gasket seal when mating the t-stat housing due to lack of fiber gasket.

Drove to work today and the gurgling sounds are now gone (fingers crossed).  I think my old pump was shot, allowing *some* drips of coolant to come out the weep hole as well as a *LOT* of air getting in.  As for the large loss of coolant, I think that was actually coming out of the expansion tank overflow tube.  It came out when a large release of air forced tons of bubbles causing fluid to splash around in the tank (going out the overflow hose) and spilling onto the front differential.    This only happened when driving, and is the reason why there was never a large puddle under it when parked.  I actually caught it once when pulling into a parking lot. 
 
Sorry for my ignorance, but I didn't read the other replies.

I have a similar issue as you. Loosing lots of coolant, no leaks anywhere. When I changed my oil, I had lots of goo. After abotu 6 months of testing different things, I am currently in the garage swapping the heads. My 706 heads cracked and allowed a lot of coolant to rush in after the engine was shut off.

See my post if you have any questions
 
The oil was the first place I looked.  Luckily it was not contaminated.   Sorry to hear about your heads, what a bummer  :-(   

In my case it was only the pump (thankfully), even though it was odd to me that a pump I just bought 2 years ago would fail so soon.   Even more odd is that the symptoms were different from the time I lost my original pump.  I don't remember a lot of air entering the system the first time.  I guess it just depends how the water pump fails and maybe what brand of failed water pump.
 
I was loosing the same amount of coolant, only no evidence at the weep hole. Oil was fine so I bought a replacement pump hoping for the best. Turns out one of the metallic seals had corroded in the area closest to the outside of the pump. Very small hole at that. Never saw any fluid there. Changed the pump anyways.
 
I was nervous about it getting into the oil at first.  I can't remember what percent water in oil is visible... thinking about testing this with some used motor oil.  After I lost an entire quart of coolant, that would be getting close to 20% contamination.  That would definitely be visible if indeed in the oil.  Hell, even 8oz is roughly 4-5%.  I bet this could be easily seen.

 
Lifted07 said:
That's bizarre, I just looked at my casting number and it is a 243.  Are these good or bad ?
The 862/706 heads may have only applied to prior to 2007 I am not sure.

Rodney
 
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