Tag Archives: stop leak

Radiator Stop Leak For A Heater Core Leak

Heater Core Leaking?

Using radiator stop leak for a heater core leak is usually a simple solution. Depending on the situation it may be your only option but you must be aware that you may be giving yourself a bigger problem then you are attempting to solve. Most heater core leaks are small and will not cause an immediate significant drop in coolant level unless a connection tears loose or a tank blows off because of excess pressure. While these situations are uncommon, they do happen. You normal small leak should respond well to a little stop leak while a much bigger leak probably will not.

Do you smell coolant?

A leak within a cooling system is usually noticed by a rise in the temperature gauge, your engine hot light coming on or the smell of antifreeze. it is a very distinct smell and once you have experienced it you should recognize the cooling system odor. If you are on the road and smell antifreeze it is best to find the nearest exit and do a visual check under the hood and checking under the vehicle for leaks. You may need a radiator repair, or maybe a hose has started leaking.

If your heater is leaking you will probably not see any leaks under the engine but might find them inside your vehicle under the glove compartment. Feel the carpet on the passenger side under the glove box. If it is wet you have a heater core leak.

You may also find that your windshield  will fog up which means you are getting moisture out of your vents from the heater core. Radiator Repair

If your heater is leaking you can add stop leak and it will probably stop the leak. It will also probably stop your heater from providing the proper amount of heat to your vehicle.

Your heater core is actually a little radiator that dissipates heat generated from your engine into your vehicle. It is really small like the size of a hardcover book and about a tablespoon of dirt will plug it up to the point that you will not get any circulation and thus no heat. So if radiator stop leak works for a radiator repair it should also work for a heater core repair.

So in an emergency the stop leak may fix your cooling system problem and but may also restrict the proper functioning of your heater core. Some car heater cores cost a lot to replace as the heater is under the dashboard and very difficult to remove and replace. Your whole dashboard may have to be removed and in some cases it can cost between $500 to a $1,000 to remove a heater core and most of that cost is for labor only, the part will be extra. This is also a good time not to bring your own part to the dealer to install. If your heater starts to leak again you will want a warranty on both the parts and labor. If you provide your own part and it starts to leak the dealer will have to charge you the labor all over again.

If your car is old and you are watching your expenses you may want to throw some stop leak in and take your chances. Your may also help plug up your radiator or other parts by doing this but it is all up to you. Pay them now or pay them later.

Disconnecting your heater core

Another option you may have instead of using radiator stop leak is disconnection your heater core. If you look under the hood you will see two hoses connection the heater core to the engine. You can splice these two hoses together to bye-pass the heater completely and stop the coolant from running through your heater. You will need to fix your heater core before cold weather arrives but you will be stopping your heater core from leaking, for now. Please note that many heater cores have two different size hoses and if yours does you would need to either block them both of them off separately or buy a fitting that connects two different size hoses. Check your auto part store, some offer these fittings.


If I had a cheaper car and had a small leak and funds were an issue, a little stop leak would be my answer. Stop leak works but don’t pour in four bottles.  Start slowly, half a bottle and use no more than you need.

Don’t buy the most expensive stop leak.  I know you get what you pay for but this is stop leak. If the cheap stuff doesn’t work the expensive stuff probably won’t either. I just had a water pump leak on my vehicle and went to AutoZone for some stop leak as I was on the road. The $5 stop leak worked fine and I was able to get home and replace my water pump. I did not buy the $25 bottle of stop leak and that was a good choice in my case.