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Found Puddles Under Your Car or Truck? How to Diagnose Coolant Leaks!

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Hey friends, it's Len here from 1A Auto. Today we're gonna be talking to you about how to find coolant leaks on your vehicle. We've got a GMC 1500 in the shop. Let's jump right into it. Now you're only gonna need a little bit of safety gear and some simple tools. We'll get right into it right over here. So just put these down. We're gonna come right over to the hood. You feel on your radiator cap. If it feels as though it's hot, you don't wanna open it yet. Assuming it's cold, press down, turn to the left and open it away from your face. We'll take a look at the radiator cap and make sure that the seal looks good. If the seal's dry, rotted and cracked, it needs to be replaced. You'll also notice you have a little pressure thing here. Okay. That's for venting. The way it's gonna vent is if you were to look right here, you're gonna see a number and it's gonna tell you how many pounds of pressure this is supposed to hold. Once you build up too much pressure inside the system, it's supposed to vent. If this spring gets weak over time which it will, it's probably gonna vent at an earlier stage. So this is supposed to be at approximately 15 pounds is when it vents. Maybe it's gonna go 12. Maybe it's gonna go 9. Who knows? Maybe it's just gonna leak as soon as you start up the vehicle.

This one, you'd wanna just test it with a little tester or of course, you can replace them. They're fairly cheap. Overall, there's a possibility of two different types of leaks on a vehicle. There's gonna be an internal leak or an external leak. When we're talking about coolant, more than likely if it's an external leak, you're gonna see it externally off of the engine or even one of these hoses that comes off of your radiator or even over by your firewall where your heater core is. If it's an internal leak, more than likely you're not gonna notice any types of drips at all but what you will notice is a funny smell coming from your tailpipe and/or some smoke. Now if you notice that you have a coolant leak and it's an external leak and it seems to be dripping down on the ground, it's probably gonna be fairly easy to find. If for some reason you notice the drips but you can't tend to find where the actual drip is coming from, you might need a tool that's as simple as a pressure tester like this. You would just screw it right on, pump this up and then you wanna get it up to approximately 15 to 20 pounds of pressure. Once you have it there, you wanna let it sit for a little while and you wanna see if that gauge drops down.

If the gauge goes 10, 9, 8, 0, whatever, you know you have a leak but at the same time as this is happening, more than likely if you were to look down at the ground, you're gonna see drip, drip, drip. At that point, go ahead and get on your safety glasses which I have mine on all the time when I'm working on vehicles and of course, my hand protection. I'll get underneath there with my flashlight and I'll take a peek and I'll try to find where it's coming from. Let's go over a couple areas where it might be. So we talked about testing the radiator cap already. That's more than likely the simplest solution for any of this. Other areas that you might wanna look would be the upper radiator hose where it connects to the radiator. You could also follow it down to the other end where it connects into the thermostat housing. If it's leaking anywhere around there, of course you'd wanna fix it. You're also gonna have the lower radiator hose which is probably gonna go from the water pump into the radiator. Other leaks would be where the thermostat housing actually connects on to the engine right down here. The gasket can go bad. That's obviously gonna be an issue as well. And if you were to continue on towards the front of the engine, you're gonna see where the water pump is and it's gonna have a pulley that leads right to your serpentine belt and it's probably gonna have the fan mounted to it like this.

Anywhere where you have a coolant tube that leads in to the water pump is a potential area for a leak. If I was to shake this around, I can see that there's moisture right inside this seal right here which is telling me that this is leaking for sure. I can also tell because well, this all looks like it's very wet. I don't even have to put the pressure tester on it to see that. Another thing that might leak is if you were to look at the radiator, you have that seam where the tank actually connects on to the finned area or the aluminum area of the radiator. It's very common for the seal that's in there to leak so you'd wanna check that as well. You can generally see that if you were to pressure test and it's gonna be right down along the side. If you were to go right down along the backside of the engine where the firewall is, you're gonna see your heater hoses. They lead into the firewall right where the heater core is and the heater core is located right behind the glovebox, generally speaking, on most vehicles. If there's a leak between where the hose connects on to there or even a leak on the heater core, if there's a leak on the heater core, you're more than likely gonna notice it on the passenger's side floor of the vehicle.

So following that heater hose, it comes all the way this way and then you'll see the point where it goes ahead and connects into the engine, that's another common area for vehicles to leak. So this one actually looks like it's leaking as well. If you have coolant that you see coming down the back side or even the sides of the engine, more than likely it's coming from the head gasket or even potentially the intake gasket. If you happen to see coolant coming along the front, it could either be from, like I said before, either the radiator or even maybe those fittings or the hoses that connect into the radiator from the engine. On some vehicles, not necessarily this one, you might actually have rear climate control which is gonna have coolant tubes that run from the front to the rear and that's gonna go back to the heater core there. So if you need a little bit of heat, you can just crank it right up. While those tubes, being aluminum as they are, tend to corrode especially along the areas where they connect into something else and they have a possibility of going bad over time. Another place you might notice the internal coolant leak would be coming out of your oil pan.

Maybe you're doing an oil change and you get that coolant that's gonna come out first and then it'll be, of course, the oil because oil floats on top but if you have coolant inside your oil pan, that means you have a head gasket problem. Another thing that you're probably gonna notice is smoke coming from your tailpipe. It's gonna come billowing out white and it's gonna smell kinda sweet. It's not anything good to smell. I wouldn't wanna smell it for a very long time because it is technically toxic. If you have white smoke coming out of here, more than likely it's because coolant is getting inside of your combustion chamber and then getting blown right out of the tailpipe and causing that white smoke. Another way to test for an internal head gasket leak would be right up here at the radiator cap. You'd buy this little tool. It's kinda like a clear tube and it's gonna have an area for a liquid. It comes with a special liquid usually and it has a little bubble on top. Okay. You put in some of this special liquid, it's gonna be blue and then you put on the bubble afterward and you bring it right over here. You'll open this up carefully and away from your face. Put it right over the top.

Now you would just kinda pump that little bubble on top a couple times and it's gonna kinda pull the air or you know, vapors from inside of your cooling system and if there's any carbon monoxide that's coming from your exhaust getting pushed through that head gasket into the cooling system, it's gonna change colors of that fluid for you and then you're definitely gonna know that you have an internal coolant leak. Now if you were to come over to your oil cap and remove it and you saw some white cream all inside here and it looked kinda funky, that's because there's moisture inside of your valve cover housing here which, of course, moisture more than likely could be from coolant or it could just be humidity but it's definitely mixing with the oil and it's causing that film. Now obviously if you're dealing with a different type of vehicle instead of the one that I'm telling you about, you're gonna wanna check all the usual places, the radiator, the coolant hoses, the thermostat housing. You're gonna check over by the heater core where it goes into the firewall there. Check for all those external leaks. If for some reason you don't find an external leak but your coolant is still going low, more than likely it's an internal leak like we talked about before. In which case, you'd go about doing all of the same testing.

You can use that little tester, the little bubble like I told you about. If the fluid changes colors, you know you have carbon monoxide inside your cooling system. If you see smoke coming out the tailpipe, more than likely you have a head gasket problem and there's coolant going inside that combustion chamber and getting forced out that tailpipe. All right. So if you liked the video, make sure you click on that like button. While you're at it, go ahead and subscribe and ring the bell. And if you saw something you like and you wanna talk about it, tell me about it in the comments section. Thanks.

Thanks for watching. Visit 1aauto.com for quality auto parts shipped to your door, the place for DIY, auto repair. And if you enjoyed this video, please click the subscribe button.


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