Coolant leak help

operator556 · October 16, 2015

So my Yukon with 160k on it started having a very slow coolant drip. So slow you wouldn't notice unless you let the truck idle for 15 minutes in the driveway. Then yesterday on the way home I stopped at the store and when I came out there was coolant everywhere and it was basically pouring from the front right of the motor. I checked the reservoir and the coolant level was normal. Then I drove it home and the temp started to rise from its normal spot at about 150 to 210. I pulled over so it wouldn't overheat and turned the heat on to cool it quicker. But the air was cold not hot and normally the heat can cook you out of the truck. Looked under the hood again and reservoir is full but the radiator was bone dry luckily I'm always prepared and had 4 gallons of coolant with me and filled the radiator. The trucks temp was normal the rest of the way home and the heat was hot as usual after filling the radiator. After pulling in my driveway the radiator is near empty but my reservoir is still full of coolant. I can't find the leak doesn't come from the front of the water pump and the hoses are good. Seems to be leaking somewhere around the passenger side of the water pump. Could it just be a bad deal between the block and pump after 160k?

ifixedit · October 16, 2015

First off I see your Yukon is a 99, these years had issues with the intake gaskets crumbling due to the red Dexcool coolant eating them up and all of a sudden the thing is going through coolant like there is no tomorrow. Prior to this happening, have you had a slow loss of coolant over time and you find you have to top it off once in awhile? Your turning on the heat trick did not work because the coolant level was already too low and there was not enough coolant in the system to fill the heater hoses and heater core. As far as you know have the intake gaskets ever been replaced? If not and they're the originals it's time. One tell tale sign is pull the oil dipstick, if the oil is milky you need to get working on it right away, don't drive it any further, the intake gaskets need to be replaced like right now!

If the oil is not milky colored and it seems from what you describe most of your coolant loss is external, water pumps on their way out can get a little funny. They will leak like crazy one minute and then go two days and will not leak at all. Usually when the weep hole on the bottom of the pump leaks, it usually happens after you have drove it and it is fully warmed up with pressure on the system, you park it like you did and come out later to a large puddle under the truck. If you crawl under the truck with a flashlight and point it right at the weep hole on the pump, I'd bet you see coolant leaking from the weep hole and the front of the block will be wet under the pump. If you can determine for sure nothing else is leaking (radiator, hoses, etc.) and no coolant is getting into the oil, if the water pump has that many miles on it I'd go ahead and just change the water pump.

operator556 · October 20, 2015

I changed the intake gaskets maybe 2 months ago. It had a little miss that took me forever to track down but it ended up being the intake gaskets. This leak is most certainly external as it just dumps right onto the ground when you pour it in the radiator. I'm just going to go ahead and replace the water pump this weekend. Hopefully that's my problem

ifixedit · October 20, 2015

The way you describe things "just dumps right out onto the ground" makes it sound like the lower radiator hose is possibly split or there's one big honkin hole in the radiator somewhere. Does the radiator even hold coolant? If you look inside the radiator with a flashlight, can you see coolant? When you add coolant does it leak when the engine is running or when it's off, or both? It could also be one of the side tanks on either side of the radiator is leaking. The radiators on those years in my opinion are kind of wimpy and over time it doesn't take much other than normal wear and tear, vibration, etc., to make them leak. Like my 98 Yukon, yours should also have the radiator with the plastic side tanks, so you could be due for a new radiator. If you need a new one they aren't overly expensive, I picked up a new one a couple of years ago for my Yukon for $150 at Carquest. When it does leak, crawling under the front of the truck with a flashlight should certainly show where the leak is at.

operator556 · October 20, 2015

Radiator and hoses are fine. Trust me I've tried getting under over and looking from the sides. I can't see where it's coming from no matter how I try to look at it. The alternator bracket is in the way. Definitely coming from the engine not tanks hoses or radiator. It's coming from the water pump area

txab · October 20, 2015

WP gaskets

ifixedit · October 21, 2015

WP gaskets

Definitely another possibility. If you're 100% sure it's not the radiator AND the water pump has considerable miles on it, then it's got to be the pump, the gaskets as txab mentions could also be deteriorated. Might as well just jump in and get under the hood and get at that pump.

operator556 · October 28, 2015

So I bought a new water pump and when I pulled the old pump off the gasket on the passenger side was basically non existent. That was my leak. Went ahead and replaced the whole pump anyways. For $40 how could I not. Doesn't leak now!