My garage found a small amount of dried coolant on my radiator and block heater and tell me that I needed to replace my radiator, block heater, and hose urgently, as it could leak at any moment.

I last topped up my coolant about 6 months ago and it doesn't need topping up now, which suggests its not a new leak.

I was about to go ahead and get the work done, when googleing found K-Seal

Will K-Seal work almost as well as an expensive repair, or is it better just to get the work done?


My garage found a small amount of dried coolant on my radiator and block heater and tell me that I needed to replace my radiator, block heater, and hose urgently, as it could leak at any moment.

In order for there to be coolant residue on the outside of places that it should inside that is clear indication that there is or was a leak. Also, seeing the flaky, dried up build-up is an indication that the coolant has been leaking at that point for quite some time, in order for it to build up into the pile you see.

If you are checking for the leak while the vehicle is cold and in your garage then this is not the how it should be checked. A small leak [like the one being described in your post is going to be present only when the coolant system is pressurized.

If the system is cold (sitting overnight or long enough where the engine is equal to ambient air temperature) then it must be pressurized using a device called a Coolant Pressure Tester. If you were to purchase one of these then you must make sure the adapters for it are for your specific vehicle. There are many different styles different make and model vehicles.

If the system is hot (at normal operating temperature), and the leak is big enough, then you might be able to visually see the leak. If not, then you will have to wait until it cools down (in order to ensure that there is no excess pressure in the system) and then pressure test it.

Once you've identified where the leaks are then look into replacing those components.

It is never recommended to use any type of radiator sealer additive. These products tend to raise the pressures in the system causing more strain on the surrounding components involved in the system. They also, will deposit themselves wherever they land in the coolant system (not how they make it look in the commercials where it goes directly to the leak and creates a perfect patch).

The reason why they make it look the way it does in the commercials is because in a perfect world or a controlled / simulated environment then that's how it would work out. In theory the liquid should take the path of least resistance. In this case, that would be the point of the leak. But, different vehicles handle their cooling differently and it's not a "perfect / simulated environment".

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    I agree with the comment but I don't think it merits a -1... – R.. GitHub STOP HELPING ICE Mar 26 '13 at 5:57
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    @hillsons, Here is a picture of something that I would consider a "small" amount coolant on a radiator. This radiator, was in fact leaking and taking about 4 months or so to put the low coolant light on. My suggestion to have the vehicle pressure tested even though it's not low on coolant but, there is some noticeable residue being called "hasty and poorly thought out" is rather bold. Especially since we don't know how much was put into the system "6 months ago", what the real level of the coolant is compared to however much it was filled six months ago. – cinelli Mar 26 '13 at 12:19
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    @hillsons, Also, to have the vehicle pressure tested by a reputable shop, and cooling system thoroughly inspected (he could even have the mechanic go over it with him) just to be 100%. And, the OP did not specify the spot of the location, if it was near a hose connection or by the cap, or in a spot where they couldn't possibly have spilled anything. Also, if six months have passed, there is still the possibly that the vehicle has been serviced in this time frame. If that's the case, most mechanics check and correct tire pressures as well as top off fluids during a service. – cinelli Mar 26 '13 at 12:26
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    @hillsons, I never stated that I was certain it was a leak. If you read what I wrote I said "if or was". Also, the OP states "coolant was topped off 6months ago, and it's good now.". Remember A SHOP found the residue. Not the OP. If coolant was low at the shop 8 out of 10 shops would at least top it off before the customer picked it up even if the work was declined. So the time span between top offs can be thrown out cause you don't know if the shop did or didn't top it off. The -1 given for being "poorly thought and hasty" is inaccurate and ridiculous. The -1 should be removed. – cinelli Mar 26 '13 at 13:09
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    @R.., "My garage found a small amount of dried coolant" Where in that statement does it say "I noticed" or "I found"? It's unclear what's found by the shop, recommending a trustworthy shop performs a thorough inspection is the best way to handle the situation. – cinelli Mar 26 '13 at 13:16

"...replace my radiator, block heater, and hose urgently..."

My, this mechanic must have X-Ray vision. He can see all these bad parts without a test, from some dried residue (not wet, even after you drove the car there). All these easy to get at, high labor cost items all failing at the same time, too!

What, exactly, is leaking? He can't say if it's a hose or a radiator? A good mechanic will pressure test and repair/replace the defective part, not throw a bunch of expensive parts at a problem at your expense. Run away to an honest shop.


Don't use K-Seal. Find out if it really is a leak. Use tape or a permanent marker to mark where your coolant level is in the coolant reservoir and monitor for changes. If it really is leaking, determine which specific part is leaking and replace it. Then find a new shop. One that isn't trying to rip you off.

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    Using a permanent marker or tape to check for a coolant leak is rather unprofessional. Also, there are too many variables that would make this a complete waste of time. 1. What if the vehicle is on a hill or, any uneven surface when the poster makes his initial mark? 2.) If the vehicle isn't rechecked at the same temperature as when it was initially checked then the levels are going to quite different are they not? Your "Mickey Mouse" methods of diagnosing shouldn't be taught to people trying to understand what is going on with their vehicle. Doing it the right way is the only way to be sure. – cinelli Mar 26 '13 at 12:43

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