Slowly losing coolant

[ScottyBoy]

I'm slowly losing coolant. About a quart every 2-3 months. Been going on for a little over 6 months now. No visible leaks anywhere, but I'm assuming with a leak this slow that it's either internal or it's seeping out so slowly that it will be hell to find it. A similar thing happened a few years ago, but it was leaking a bit faster. About a quart a month. It turned out to be the water pump leaking at the weep hole. So naturally, that's the first place I looked this time. I keep looking down under there with the engine cool, warm, and hot, and I see ZERO dripping or even seepage. Any other places I should look? I wish I had the money to fork out for one of those UV leak finder kits, but money is really tight right now.

 

[thechevyman]

Could be the radiator. Take off the top shroud so you can get a good look at the rediator. Look for stains or discoloration indicating a leak. A small leak could be evaporating.

If its a head gasket just watch for overheating. You could also check your spark plugs to see if any of them looked different.

 

[ccapehartusarmyINF.(ret)]

check around your water pump

 

[M Hankel]

Check the casting number on the cylinder head. If it is a 706, chances are that you have fallen victim to the Castech cylinder head problem. Google it and you will find more bad news.

Mike

 

[ScottyBoy]

I thankfully do not have the dreaded Castech heads. I verified that last year when I changed my valve cover gaskets.
But I guess I will inspect both the water pump and radiator for any signs of leaks or even stains. No sign of coolant in the oil (or at least on the dipstick) that I can see. But I did see some leaking/seepage around my AC compressor. Does not look like coolant though, looks like compressor oil, and it has a greenish color to it. My coolant is not green, I have the orange Dex-cool coolant.

 

[YukonXL04]

I'm leaking some as well. However mine oddly enough is the water pump gasket not the weep hole. It's hard to find wet spots cause it leaks down behind all the acc on the front of the engine. However mine leaves about a 2 inch wet spot on the ground every morning.

 

[chevync]

Your inside windows fogged up in the mornings? If so, could have a small leak at the heater core...

 

[M Hankel]

I thankfully do not have the dreaded Castech heads. I verified that last year when I changed my valve cover gaskets.
But I guess I will inspect both the water pump and radiator for any signs of leaks or even stains. No sign of coolant in the oil (or at least on the dipstick) that I can see. But I did see some leaking/seepage around my AC compressor. Does not look like coolant though, looks like compressor oil, and it has a greenish color to it. My coolant is not green, I have the orange Dex-cool coolant.

That's good that you don't have the castech heads.

Could be a head gasket going bad. I've seen/heard of them leaking a little bit at a time, not enough to cause white smoke etc... How's the oil looking?

As mentioned, could also be a heater core leaking inside the cab. You'd probably notice that though.

Mike

 

[bottomline2000]

yeah, you don't want the 706 crap.. mine leaks like no end. compression loss and all that fun stuff thanks to some crap heads. RTV the water pump gaskets and the leak should be gone...

 

[M Hankel]

RTV the water pump gaskets and the leak should be gone...

RTV on an LS water pump? New stock style rubber impregnated gaskets. I've reused the ones on my racecar dozens of times without a single leak.

Mike

 

[livingez_123]

if you had a leak in your radiator, you would smell it, even after its long gone the smell remains.

 

[bottomline2000]

RTV on an LS water pump? New stock style rubber impregnated gaskets. I've reused the ones on my racecar dozens of times without a single leak.

Mike

Yep, I replaced the water pump on my truck with the rubber impregnated gaskets and there was always moisture on the outside of the pump.

I also have an 05 GTO and when I replaced the pump on it I ran a small bead of RTV around the edge of the gasket and it's dry as an old bone. Didn't take much and it worked.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[M Hankel]

Yep, I replaced the water pump on my truck with the rubber impregnated gaskets and there was always moisture on the outside of the pump.

I also have an 05 GTO and when I replaced the pump on it I ran a small bead of RTV around the edge of the gasket and it's dry as an old bone. Didn't take much and it worked.

Sent from my SAMSUNG-SM-G900A using Tapatalk

Hmm, the only thing I can think of is that you either got a faulty gasket, or the surfaces were not absolutely clean when they were reinstalled. I'd never recommend RTV on those gaskets for anything but an emergency fix. It's just not needed. The GM gaskets are great, the Felpro's rate a very close second and everything else is "install at your own risk" type of thing. The cheap Chinese knockoff gaskets that usually come with a replacement waterpump are the worst of the bunch, those go straight into the garbage can IMO.

I hope this doesn't come across as argumentative. It's just that one of the great things about working on the LS engines is the fact that you DON'T have to use RTV for every gasket surface. I owned many a sbc and scraping old gasket/RTV material off the surfaces got really old. It just seems like using RTV on a LS engine is taking a huge step backwards on the evolutionary scale. I cringe when my friends ask me for help on their SBC's now. I'm getting too old to scrape head gasket material off the decks of blocks lol....

Mike

 

[livingez_123]

There are a couple of areas that a tiny drop is still needed, nothing like the old 1st gen sbc.

 

[M Hankel]

There are a couple of areas that a tiny drop is still needed, nothing like the old 1st gen sbc.

Yes, the four corners of the pan gasket where the front/rear covers mate to the block. Only needed because of the differences in surface mating areas where the other gaskets stick out slightly. I usually trim those flat with a razor blade to minimize sealant use.

Mike

 

[bottomline2000]

Hmm, the only thing I can think of is that you either got a faulty gasket, or the surfaces were not absolutely clean when they were reinstalled. I'd never recommend RTV on those gaskets for anything but an emergency fix. It's just not needed. The GM gaskets are great, the Felpro's rate a very close second and everything else is "install at your own risk" type of thing. The cheap Chinese knockoff gaskets that usually come with a replacement waterpump are the worst of the bunch, those go straight into the garbage can IMO.

I hope this doesn't come across as argumentative. It's just that one of the great things about working on the LS engines is the fact that you DON'T have to use RTV for every gasket surface. I owned many a sbc and scraping old gasket/RTV material off the surfaces got really old. It just seems like using RTV on a LS engine is taking a huge step backwards on the evolutionary scale. I cringe when my friends ask me for help on their SBC's now. I'm getting too old to scrape head gasket material off the decks of blocks lol....

Mike

In all fairness I can't say what brand of gasket I got. Didn't know there was a difference in brand quality. My GTO runs great and has had zero issues. It's not like I ran a full bead of RTV. It was only a thin layer outside the rubber portion of the gasket in case fluid did get past it.

I should be swapping the motor soon so I'll keep that in mind with the new water pump.

If it leaks u owe me a gasket replacement and a 6 speed swap lol.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[M Hankel]

You got it. Yeah the cheap gaskets are a waste of time.

Mike

 

[Wake]

Your inside windows fogged up in the mornings? If so, could have a small leak at the heater core...

That's exactly what I was thinking.

Also, how about the rear A/C and heating? I imagine that coolant must run through a tube to the back and a heater core exists back there as well. Leave a whole lot of area that could be leaking.