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Car Care & Repair Tips - September 26, 2003

What Your Mechanic Doesn't Want You to Know

Reader Question: My car is overheating and my mechanic says my car needs a new radiator. I just had the radiator flushed out a few months ago, could it be bad already?

I have written about radiators in past articles, but since I have received this request and a few other e-mail questions this week regarding radiator replacement, I thought we should talk about it again.

Let's first talk about what the term "flushing" the radiator. Flushing a radiator sounds like a wonderful thing to have done periodically to your vehicle, but what does it actually do? You probably have a mental picture of this high powered jet blast of water mixed with some kind of detergent that removes all the gunk that has accumulated in the radiator…and after undergoing this procedure, your car will not only run cooler but better, right? I mean, this gunk has probably been the source of the "engine robbing performance" in your minivan for months, right? I hate to put a damper on your parade, but we need to talk.

Most radiators today are small, made of lightweight aluminum, and crammed so tightly in the front of the car that you can barely see them-let alone "flush" them. The neck of the radiator (where you pour in the antifreeze) is usually angled in such a way that it is almost impossible to pour in the antifreeze, or even SEE the antifreeze for that matter. The inside of the radiator is made up of a honeycomb maze of rows, or "sipes" that send the hot antifreeze on a long meandering journey from left to right in the radiator. Air is being forced through fins on the outside of the radiator to cool down the antifreeze inside the radiator.

Ok, I hope you are still with me because here is the answer to the question. Where does dirt and sediment accumulate in the radiator, at the top or the bottom? The bottom of the radiator will trap the majority of the rust, dirt and sediment. You can try as hard as you want to, but you will not be able to remove enough of this compacted material to cause any real significant improvement in engine performance. The radiator's internal design prevents the access of any high pressure action that you might be able to insert into the small opening of the radiator neck.

At my shop the procedure "flushing" the cooling system has been replaced with "draining and refilling" the cooling system. We remove the lower radiator hose, or if the radiator is equipped with one, using the radiator drain cock to drain out the old antifreeze. We then add new fluid. Of course, draining the radiator will only remove any minor surface debris along with the old contaminated fluid, and will probably not cure any over-heating complaints you might have been experiencing. Calcium and rust buildup within the sipes are the main causes of radiator stoppage, and will cause over-heating. If this is the case, removal of the radiator from the car for disassembling and rebuilding, or replacing the radiator, are really the only two viable options.

Yes, there are many "radiator flush" additives on the market, but most are not to be used in aluminum radiators (which all newer vehicles are equipped with), or just flat out don't work. There are very few (ok, probably only one or two) problems with a motor vehicle that can be solved by the contents of a can.

So, in a nut shell...draining and refilling your radiator with new antifreeze every two to three years WILL help maintain and extend the life of your vehicle, but will probably NOT have an impact on the way it drives, overall fuel economy, cure a major over-heating problem, or improve handling in wet weather. Ask your mechanic to inspect the radiator and heater hoses, and test or replace the radiator cap when replacing the antifreeze.

Another scenario that would require replacement of the radiator is an external antifreeze leak. The seals that join the pieces of the radiator together can become brittle and leak, or debris from the road can puncture the skin of the radiator and cause a leak. So the inside of your radiator could be fine, but damage to the outside might be why your mechanic would like to replace it. The cost of a new radiator has dropped significantly in the past few years, so replacement might actually be more economical than repairing it.

Incidentally, a vented radiator cap will come in real handy when you need to check the antifreeze inside the radiator and don't want to wait for the engine to cool down. The vent release on the cap will remove the hot dangerous steam instantly and allow you to inspect inside the radiator even when the engine is hot. You can not safely do this with a regular non-vented radiator cap. So if you don't have a vented radiator cap, choose one the next time you replace your antifreeze.

So that's enough about radiators for this week. Stay tuned for next week's exciting adventure as we explore the world of ball joints (maybe!)


Austin C Davis

Austin C Davis

Interested in an e-book about everything your mechanic doesn't want you to know? Sound advice from Austin Davis. Click Here!

The above article is provided for the interest and entertainment of our visitors. The views expressed in this article are only those of the author, who is solely responsible for the content. AutoGuide.net does not endorse any of these views, and is not to be held responsible for any of the content provided in the above article.

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