Blown Head Gasket Symptoms

Reader Question

Hi Austin, my old Toyota Corolla might have a major internal coolant leak as per my mechanic who seems to think I need to get a new car.

Can you tell me what are the common blown head gasket symptoms I should be concerned with? He wants to charge me $1,100 to replace the headgasket.



Hello there Jennifer,

Yes, I can see where you would be a little leery of putting that kind of money in an older vehicle. There are a few common blown head gasket symptoms I would be looking for and they are.

1. White smoke from the exhaust pipe  – When coolant is leaked inside the cylinder the spark plug tries to burn it like it would gasoline and it can not. So what you see out the tailpipe is white smoke/steam

2. Constant loss of coolant – if you are continually adding coolant to the radiator and see NO obvious external coolant leak anywhere.

3. Running rough – engine miss firing. When the coolant/water enters the cylinder it will basically put out the spark from the spark plug and that cylinder will not be able to fire and do it’s job. So what happens is that cylinder is “dead” and you will feel a missfire because of it. The engine will run rough, try to die and will get poor fuel mileage due to the miss.

4. Lack of engine compression – since there is a tear or hole in the headgasket on one or more of the cylinders the cylinder can not hold pressure.  If you were to do a compression test on all cylinders you would notice a drastic drop in compression on those cylinders with the headgasket leak.

5. Coolant inside the engine oil – not all the time, but sometimes the engine oil will get mixed with coolant from the headgasket leak and cause the engine oil to look like a chocolate milkshake instead of clear to dark brown or black looking oil.


What should you do first?

Get a cooling system pressure test to help you determine if you have an internal (headgasket) or external coolant leak (hose, water pump, radiator etc.)

Once you think you are sure you have an internal leak, I would then do a compression test to make sure only 1-2 cylinders are affected and not a total loss of compression across all cylinders.

Now, before you just run out and spend $1,100 on a headgasket replacement try this first.

Headgasket Sealers

I have used this headgasket sealer for many many years with a great success rate. Do it like this NOT as described on the can.

1. Get a can of K&W Engine Block Sealer – or the new Nanotech Block Sealer by K&W from your local auto part store.

2. Mix that can in a bucket with plain tap water and mix together

3. Drain out all the coolant from the engine and radiator as best as you can.

4. Pour in the contents of the bucket and top off and mix using a water hose.

5. Now, drive the car for a total of 500 miles to help get the sealer into the hole in the headgasket and plug it up.

6. After the 500 miles drain out the radiator and sealer from the engine.

If the sealer worked, it should be a permanent seal.  You need to make sure you repair the initial cause of the overheating though as the headgasket failure is just the symptom of the overheating problem.

You will NOT have freeze or boil over protection during this 500 mile period so keep your radiator and engine from freezing.

This really works well, and I hope it works for you too.

Feel free to comment, share on Facebook etc. and help your friends save a ton of money.

I made this video for those of you who do not want to read :)


Austin Davis


Posted in: Coolant Leak

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."
  • Austin Davis

    Yes John, the K&W sealer would be worth a try in this case. Let us know what happens.

  • John Colvin

    I have a 3 cylinder Lombardini diesel engine that I noticed the oil was milky and thought may be getting coolant into the pan. There was also pressure in the radiator when running that would push water out the overflow tube. The engine was not getting hot when running at high idle. I could not find anyone to do the work on the engine so I decided to try. I assumed that it was a head gasket and the shops also thought that. I removed all the gingerbread parts and was about to take the head off and was having trouble removing the head. The service manual warned about excessive prying and hammering. I read your comments and now I think I should retorque the head and reassembly the engine and try K&W sealer. I had tried an other brand with no luck. I did not get a pressure check on the cylinders because I did not have the equipment

  • Austin Davis

    I would find another mechanic and start from scratch with a cooling system pressure test, check for a radiator restriction, check electric cooling fans etc. Does not really sound like a head gasket issue (from what you have told me) so rule out the easy stuff and go from there. Here is my video on overheating problems. let me know what you find.

  • Me again. After reading the symptoms of a head gasket leak, I’m filled with even more questions.
    1. No White smoke from the exhaust pipe – not that I or anyone else has seen

    2. Constant loss of coolant – Definitely loss of coolant.

    3. Running rough – . NO. Runs smooth as butter, unless it gets too hot

    4. Lack of engine compression – No. Seems to run great when I test drove it after we changed the thermostat and replaced coolant

    5. Coolant inside the engine oil – No. Oil on dip stick looks like normal; no carmel or cloudy color, etc.

    What do you think? Would putting H&W in hurt even if it wasn’t needed?

  • Austin Davis

    You are very welcome, glad my site has helped you save some money. Let me know if you need anything else from me.

  • Arnold White

    Thank you for sharing your knowledge, you just saved me more than 1000 dollars. At first I had a little trouble putting all the thing together in order for the sealers to work but after I carefully followed the steps you wrote it worked. Thank you very much.

  • Austin Davis

    Well, if you still have your old truck, try the KW block sealer additive to repair the headgasket, it really works.

    If the dealership replaces the headgaskets AND does a valve job on the cylinder heads I think you will be fine as long as the CAUSE of the original overheating has been repaired as well. So if the radiator is stopped up for example, the engine will overheat again and cause problems.

    If the dealer is NOT going to do a valve job at this time and just going to slap on the gaskets, ask them to give you the cylinder heads and you take them to a machine shop to have a valve job done on them, (cost about $200) this will basically rebuild the top end of the engine. You will need to take the valve stem seals with you to the machine shop.


  • Emery

    Dear Austin,I just went in to buy a used car because I am having problems with my Durango.I am tired of putting money into it because its a 98.The head gasket is shot.So I finally found the truck I want but my luck the head gasket is shot on that as well.The used one I’m buying.The dealer is fixing it before I buy it,but my question is this should I still buy it and what problems could occur down road if I do?