Identifying an Engine Coolant Leak

coolant leakIf you’ve got an engine coolant leak in your vehicle you’re probably getting extremely tired of popping your hood every couple of days to check it.  It’s a good thing to look under the hood of your car regularly for leaks, worn belts, broken hoses and that sort of thing, but doing that maybe once per month should be good enough to catch problems before they get really bad.

Unless you’re very meticulous with your inspections, most car owners find out they’ve got an engine coolant leak either from a low coolant warning light or from your vehicle starting to overheat.  Allowing your engine to overheat is one of the quickest way to do damage to your vehicle’s engine and end up with a hefty repair bill.  Allowing your car to overheat is second only to running your engine with low oil in its ability to do quick damage.

The most common causes of overheating are broken water pump drive belts and low coolant levels.  The best way to prevent a broken water pump belt is to make sure you change the belt at your manufacturer’s recommended intervals and to take the time to listen to your car for signs of bad bearings in your water pump.

The best way to avoid low coolant levels is to regularly check your coolant level and inspect your engine bay for signs of a coolant leak.  Once you’ve discovered a leak, either by lowering coolant levels or from evidence of a leak, you have to identify where the leak is coming from so you can seal the leak and keep your car from overheating.

Identifying an engine coolant leak can sometimes be tricky business.  When your engine is at normal operating temperature your coolant is very hot.  This means that if it is leaking it will most likely evaporate very quickly leaving very little to no trace of that leak.  Engine coolant is also very watery, so unlike an oil leak it can blow, drip or spray to entirely different parts of your engine bay.  This means even if you can find coolant on your engine, it can take some extensive detective work to figure out where the leak actually is.  Last, your engine coolant travels all through your engine block, the head, the heater core and radiator, sometimes the intake manifold and other places in your engine bay that make just about anywhere a possible leak location.

There are a few easy tricks you can use to help identify an engine coolant leak.  First, a great test is to perform a cooling system pressure test.  When your coolant heats up it pressurizes your cooling system from the expansion which can expose leaks.  A pressure test can similarly pressurize your system which can often make the leak stronger or show up more easily without your engine having to be extremely hot.  Second, many auto parts stores sell UV dye and light kits.  You can place the UV dye in your engine coolant and drive your car for a few days to make sure the dye circulates through everything.  Then, park your car in a very dark place and use the UV light to search for your leak.  The dye will show up very brightly under the UV light and should provide a path to your leak point.

The most common coolant leaks occur in the hoses that connect your engine to your radiator or heater core, or other small hoses running coolant to different equipment on your engine.  The best way to stop these leaks is usually to replace the hose as they are inexpensive and easy to get to.  The other leaks you can find in your cooling system would be in the engine block or radiator.  Your radiator is at the front of your vehicle so it’s exposed to road debris, rocks, dust and other things that can poke holes in or crack the thin metal.  Your engine block also can form small cracks as the cast iron it is made from is a relatively brittle metal.  Since replacing these components can be very costly, it can be much easier to seal these leaks from the inside out.  BlueDevil Radiator and Block Sealer is a chemical sealing agent that you can add to your engine coolant.  It will then seek out leaks in your engine block or radiator sealing the leak permanently!


For more information about BlueDevil Radiator and Block Sealer, check out our product information page here: Radiator and Block Sealer

You can also purchase BlueDevil Radiator and Block Sealer at any of our partnering local auto parts stores like:

  • AutoZone
  • Advance Auto Parts
  • Bennett Auto Supply
  • CarQuest Auto parts
  • NAPA Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys
  • Fast Track
  • Bumper to Bumper Auto Parts Specialists
  • S&E Quick Lube Distributer
  • DYK Automotive


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coolant_leak.jpg – By Liorpt – Licensed By Thinkstock Photos – Original Link


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18 responses to “Identifying an Engine Coolant Leak

  1. I have a 1997 Ford F-250 Heavy Duty with a Gasoline 5.8L V8.Mileage on this truck is 245K. Last week, I was towing my boat (about 3500lbs) from Crestview, FL over to Jacksonville, FL. …about a 300 mile trip. Around 160 -170 miles into it I started losing power and noticed the coolant temperature rising. I backed-off of it and the temperature went down and then started fluctuating high and low. When I pulled off there was no water in the tank and about half the water was missing out of the radiator. FIlled it with antifreeze and started out again. About 15 minutes later a cloud of steam was rolling out of the exhaust and I knew the head gasket was leaking. Nursed it along (by taking it easy and not letting the temp indicator max out) with more water (as I had used all my antifreeze) until I could get to the next rest area. When I got there I let it cool and added more water as it was nearly all gone. I made it another 30 miles before the water was gone and took the next exit. I didn’t want to push my luck. Shut it off and let it cool again and it was laboring hard after I restarted it and was adding more water to it. During adding the water, it Hydraulic Locked while running and I left it off. Towed it back to Crestview and last night purchased and bottle of BD. Part #00209 (Blue Devil Pour-N-Go) from O’Reilly’s and followed instructions on the bottle to the letter. I had already pulled the plugs on the side I suspected it leaking on and cleared the cylinders of water. The last cylinder on the passenger side was full and shot water everywhere, the one in front of it had a small amount. I made sure the engine would turn over freely and that the cylinders were clear when I started it. Took one full minute while pouring it in the radiator. The engine ran in total time for about 45 minutes and although the steam coming from the exhaust went down some…it didn’t stop.
    After about 35 minutes, it was running really rough and stalled. Steam emission was high again. I started it back up and it ran for about 10 minutes severely rough and has now quit and won’t turn over at all. Presumably from hydraulic locking again in the same cylinder.
    The Big Question is…… What Now?
    I’d like to say my experience and outcome was good with this product but, that didn’t happen. I know coolant leaks and especially head gasket leaks are hard to seal without mechanical intervention. I also know this engine has a lot of miles on it and realistically, I can’t expect a cure out of a bottle or can I?
    I’ve heard 20 people swear by this stuff and say it works. Came highly recommended at O’Reilly’s and was told about the guarantee. The money is not the issue here…I won’t say the product is junk because it is recommended by way too many that have had success. I’d really like the stuff to work, as I need my truck for towing my RV, Jet Ski’s and just general hauling things.
    I don’t know where I have gone wrong with this other than, the possibility that, maybe my head gasket was just too far gone for this to work?
    Definitely give me a reply on my email. I’d like to find out what the limitations are for this product, if any.
    A success story on this truck would make my day as I’m sure it would yours, also.

    1. William-

      Thank you for your detailed explanation as to what is going on with your Ford F-250, it always helps when we have as much information as possible. You had mentioned that you used the BlueDevil Pour N Go Head Gasket Sealer in your V8 truck; you may or may not have noticed at the top of the directions where the label states “For use in 4 or 6 cylinder engines”. Due to the size of your engine 1 bottle would not have been enough product.

      We recommend that you use the 32 ounce “mechanic approved” BlueDevil Head Gasket Sealer ( This is the more concentrated of the two products and would ensure best overall results.

      Thank you!


  2. I have a 1999 chevy suburban 1500 2 wheel drive. With 192,900 miles on it and i smell antifreeze. And i have to add antifreeze often i dont see any leakes. Im not sure where the antifreeze is going.

    1. sometimes the coolant can find its way into your transmission through the transmission fluid return lines. drain your trans and see if it looks like strawberry milk. if that the case you found where the coolant is going.

  3. Hi I have a 2005 dodge neon and my coolant is somehow disappearing. I don’t see any leaks. I have took it to a shop and they don’t see anything wrong, they said its not the head gasket and I have replaced the radiator cap and the waterpump. Sometimes after driving the car there is bubbling sound after turning the car off. Also sometimes you can smell the antifreeze. Please help me in solving this problem.

    1. Shanna-

      Thank you for asking about your Dodge Neon. Do you know if the mechanic performed a block-dye test? Are you getting any misfire codes or is the engine idling roughly? Please contact our technical support team at 888-863-0426 so that we can get a better understanding of the vehicle’s symptoms and be able to make any appropriate recommendations.

      Thank you!


  4. My 2000 Bmw e46 328i keeps overheating. Sometimes the engine will start to overheat and cause minor smoke coming from it. I’d fill the coolant reservoir to the top and drive it around and in less than one hour it’d say low coolant and repeat the overheating process explained. Need help…

    1. Brian-

      Thank you for asking about your BMW 328i. In order to get the benefit of using the BlueDevil Head Gasket Sealer, the vehicle would need to be able to idle for a full 50 minutes, and you should not be losing more than about a quart of water/coolant during that 50 minutes. Based on your description, unfortunately, it sounds like you may be losing coolant a little too quickly for the product to be successful. A hard part repair may be your best option.

      Thank you!


  5. I have a 2000 Acura RL 3.5 and ive always had a problem with the car overheating. When i put water in the radiator it starts leaking from under the engine but i cantseem to find where the leak is coming from, so i dont know whether it is from a radiator pipe or maybe even the water pump. Need Help………

    1. Bobby-

      Thank you for asking about your Acura RL. Has the vehicle been diagnosed at all? Please contact our technical support line at 888-863-0426 so that we can get a better understanding of the vehicle’s condition and be able to make any appropriate recommendations.

      Thank you!


  6. I have 2004 Ford fouce with a lot of miles. For the last few months it’s been over heating if I leave it in park for to long but when I hit the gas it goes back to normal on my dashboard I know I need to get it check out but I put it off. Now it’s leaking water I can’t pin point the leak. where could it be leaking from?

    1. Holly-

      Thank you for asking about your Ford Focus. Based on your description, it would be tough to pinpoint where the leak is coming from exactly. It is possible that you are getting combustion/exhaust gases pumping back into the cooling system. You can use a “Block Dye Tester” to confirm whether or not that is the case.
      BlueDevil Head Gasket Sealer will still work if your vehicle is getting combustion/exhaust gases blowing into the cooling system and creating pressure. To give yourself the best overall chance of BlueDevil working successfully, in addition to the directions, you should remove the spark plug from the cylinder with the leak; this will be the spark plug from the cylinder with the low compression reading. If you are not sure which one that is, you may pull all of the spark plugs and will notice one will have a white-crystal-like substance on it and/or may look dirty; this is the plug you should pull. Leave that plug out for the 50 minute idle in order to relieve the pressure from building up and thus allowing the product to seal properly. Be sure to follow the guidelines for the proper amount to use based on the size of your cooling system.

      Thank you!


  7. My 97 buick lesabre is leaking coolant. Ive just changed the radiator, the upper and lower radiator hoses, and the belt tensioner due to a leaking elbow. and its still leaking from somewhere. any ideas?

    1. Penelope-

      Thank you for asking about your Buick Lesabre. Based on your description, we recommend using the BlueDevil Head Gasket Sealer to help stop your coolant loss. As long as the vehicle will maintain idle for a full 50 minutes, and you are not losing more than about a quart of water/coolant during that 50 minute run, you would be a great candidate for the product.

      Thank you!


  8. I have a 2007 ford explorer 6cyl, I got done replacing My radiator, thermostat, and my heat accessory hose. It drove perfect for about almost 2 weeks, with heat which it didn’t have before. Now it is leaking coolent fast, while in idel and driving. I rechecked all my hose connections they were replaced and all are secure. I also still get heat. Could you help me digose the problem? If you need more informations please let me know!

    1. Shai-

      Thank you for asking about your Ford Explorer. Are you noticing any other symptoms such as white smoke from the exhaust or water/coolant getting into the oil? Has anyone been able to identify where the leak is coming from or is it losing coolant internally? Please contact our technical support line at 888-863-0426 so that we can get a little better understanding of the vehicle’s condition and be able to make any appropriate recommendations.

      Thank you!


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