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Whats That Sweet Smell from My Car Coolant Leak

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Created on: 2019-10-17

Watch this video to learn how to diagnose a sweet smell coming from your vehicle. It may be a sign of a coolant leak!

  1. step 1 :Visual Inspection
    • Check the coolant overflow tank or reservoir level
    • Check following locations for signs of leakage, such as crusty residue
    • Around the upper hose and radiator fittings
    • Around the thermostat housing
    • Around the water pump pulley and seals
    • Around the heater hoses and lines to and from the heater core
    • Around the lower radiator hose and fittings
    • Around the radiator tanks and core
  2. step 2 :Pressure Testing
    • Use a pressure test tool to pressurize the coolant system
    • Refer to the vehicle manual for the cooling system pressure limit
    • Excessive pressure in the cooling system could damage your vehicle.
    • Use a pressure test tool to pressurize the radiator cap
    • Refer to the radiator cap for the pressure limit

Tools needed

  • Coolant Pressure Tester


Hi, everyone. Sue here from 1A Auto. Today I have a '14 Wrangler in the shop, and I noticed when I walked by I had a little bit of a sweet smell from the engine right after I shut it off. I thought, I think that's going to be coolant. So, here we are. Let's do a quick diagnostic and see what we find.

The first thing I want to check is the level in the overflow tank. If the system's working properly and there is no leaks, this coolant level should be up on one of the markings, whether it's cold or hot markings. Now this engine is still slightly warm. I just got here probably about three hours ago and it is way down in the low mark. I know that that means that there's more than likely seepage somewhere or hopefully not burning it. Let's take the engine cover off to get a better visual of everything, and then I'm going to take the air breather top cover off and the hose into the intake, so I can see right down in that engine compartment where the water pump is, the upper hose and the lower hose.

I'll start at the top radiator hose and I want to check for quick visual, see if I see any coolant leakage or what we call in the industry "coolant crusties," a little residue that dries up. When it gets hot, it burns and it leaves a scaling material behind. So far, it looks really good. I don't see anything here. So I'm going to follow the hose down, going to go to the where it connects to the thermostat housing. I have noticed on this style thermostat housing that has an actual air bleeder in it right here. There's an O-ring that sits in there. Sometimes I've seen it seep out of here, so that's something really close to look at. Check your clamp out, like I said. Give the hose a visual and a feel. You want to be able to squeeze it. You want to be firm but soft, not collapsed, not brittle.

Check your gaskets where it hits the block. Everything looks good there. I don't see any signs of anything. This is the water pump right here, and there's a lower hose where it connects there. Can do a quick visual there. Now I have a mirror on a stick that you can pick up at any parts store. It's very inexpensive. And I will bring this down here, shine a light on it, and now I can see the bottom part of my water pump. I don't see any traces of coolant, dry coolant. That line in between the two pieces of aluminum, that is the metal gasket. So I don't see anything, looks good.

So now that we've checked the lower radiator hose and the upper hose and the water pump in that area, I'm going to follow that heater hose right up into the heater core, and I'm going to find any other hose that goes off of it. Every car is designed differently in the sense of there, sometimes there's extra coolant tubes that go to throttle body. Some actually have coolant cool-down alternators. So once you find a hose, just do a general check. Follow it everywhere it goes. And then it goes right into the firewall and you'll see the hose says "HTR," that's for heater. You've got an inlet and outlet. Those look fabulous. I see nothing, no signs of cooling anywhere.

I'm going to follow this low hose from the lower part of that engine right into the radiator, and I could see the clamp. I'm going to take this cover off the top of this radiator because I really want to look at the scene where the radiator tank meets the core. Now we have a great visual; that plastic cover's gone. I can clearly see my radiator tanks and the seams where they meet the core, and I don't see anything.

So now that we have the engine cover off, this little plastic shield on top of the radiator, we're going to be able to see everything. We gave it a quick visual, nothing noticeable. Now it's time to put the pressure tester on the coolant system. If you don't own one, you could always go to a parts store. They do loan tools out. They aren't that expensive, probably under $200 at a local tool store, or you can go to your local garage that you deal with and ask them to pressurize the system. First thing's always make sure it's cool. This car's been sitting for over four or five hours now. It's not even warm anymore. So I'm going to take my cap off, and that's push down and turn counterclockwise. There's two stages to it. Now you're going to want to check your actual level of coolant. It is right on the top, right where it should be. That's awesome.

So it could be a minor seep or could be the radiator cap. These actually have a big fail rate after a certain amount of years and mileage. It's spring loaded. You could see that spring, and it's supposed to release pressure right through here. Most caps will come stamped with the actual pressure. This is 18 PSI. So after 18 PSI, it'll open this up and let some steam out. Not visual that you're going to see like you pull over on the side of the road. You'll never see it, but this is where I could be smelling the coolant also. If this cap is under, if it's defective, the spring has grown weak. Therefore, it releases pressure before 18 PSI; you're going to really smell coolant. So let's get the tool and pressurize it.

Now we're going to pressurize the coolant system with this pressure tester, and you just place it on just like a radiator cap. It's got the two notches. Turn it till you feel it stop and make sure that this is loose. If it's pressured, it's not going to hold, so you want it loose. Then we have our gauge, and it has the numbers right here. The red zone is too much pressure for a car, so I'm going to just going to pump it up. I'm going to bring it right up to in between 15 and 20. Once I get up to the pressure that I'm looking at, going to watch it and keep my eye on it.

If we have a major leak, that's just going to go right down, the gauge is. When someone says, "Oh, I pressurized your system and it's holding pressure," this is what they mean. It's holding the pressure that I left it at. I don't see any major drops, changes. I don't hear fluid coming out. So now I'm just going to set this down. I'm going to walk away. I'm going to come back every five minutes or so and check that pressure and see how much it's dropped, if it has dropped.

So it's been about a half hour and I checked on it twice. I came over and looked, and this is all it's moved in 30 minutes. So we're going to say that's normal, going to compensate for just the gaskets inside the tool, the gasket on this, the rubber hose. That's not dropping any pressure, so we're good as far as I'm concerned. There's no puddles underneath, so we're going to rule out any actual external leaks.

We're going to check the pressure on this cap and see if it holds pressure. I have a pressure tester that adapts to this adapter. I'm going to put the cap on, make sure it goes all the way around and locks. It's bottomed out and we have 18 PSI. So I'll take my gauge, do the same thing, make sure it goes all the way around. It's locked, the pressure's off, and now I we'll go up to 18 PSI. If it doesn't go up to 18 and it keeps leaking air, then that tells me that spring is no good and the gasket's not sealing. It dropped pressure already. Let's see if we can even get it up to 18. It won't even go past 12. So that's the great news, it's just the cap. So I'm going to get a new cap and we'll test it, make sure it goes up to 18 pounds and install it.

I went and got a new cap, 18 pounds of pressure factory setting, then install that. Let's put the tester on. Let's see what we go up to... there's 15. Yeah, goes right up to 18, releases. It's not going to hold at 18; that's what it's designed to do. Perfect, right at 15 and we're all set.

So a quick recap, we checked all the possibilities of where we could have a coolant leak, where externally burning so we could smell that sweet smell. We checked all the hose clamps, hose connections, water pump, and the radiator seams, and it ended up being that radiator cap just didn't hold pressure. So, luckily, it was inexpensive repair and we could put all this back together and go down the road.

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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