Friday, December 3, 2010

Car Cooling System Fix

General Update
Well I have definitely fallen down on updating the blog.  It's been a long time since the last post, but frankly I haven't had very much time for tinkering.  Things have been crazy with my upcoming wedding (in just about 2 weeks now), and I've just been busy with I don't know what.

I have been playing around with a few things.  I looked into HDMI-CEC interfacing, which I did a lot research on, but don't have really enough coherent information for a blog post.  It's even a little too technical for this blog.  I'd basically be restating the standard, which is freely available for those interested.

I've also, in the same area, been looking at making a HTPC, but only for ripped DVD's.  I worry about the DVD's getting scratched and misplaced.  It has happened more than once; believe me.  So the solution is to rip them all to a hard drive and play them from a HTPC.  I'm leaning away from MythTV, the de facto standard, because I really don't have an interest in the DVR capabilities.  MythTV is almost exclusively a DVR with music, DVDs, etc as afterthoughts.  I'm considering, instead, XBMC, which is exclusively DVD/Blu-ray/saved video focused.  That might make it on the blog eventually.

But to the subject at hand... I have just fixed my car engine of an overheating problem. 


Just the other day on the way back to work from a site, I noticed that my car was running a little hot.  Now this has been kind of an intermittent problem, and I believe that it is the main reason that I apparently blew a front seal on my A/C compressor towards the end of the summer (the condenser fan is apparently not working).  I didn't think too much of it, but I did make a mental note to pay more attention in the future to the temperature.

Then on the way home, I got caught up in fighting traffic and neglected to pay strict attention to the temperature.  When I looked down after a minute or two, I saw the gauge was all the way up!  I immediately pulled over and turned off the engine.

I opened the hood, turned the key to ON to let the fan run, and turned my heat on full blast.  All of these things will let the engine cool faster.  Incidentally, after thinking about it I'm not sure that it really matters whether the engine stays hot as long as it's not running.  But better safe than sorry.

I made it to the mechanic, who later informed me that he wanted to replace all the hoses, the radiator fan, and the thermostat all for the price of about $800.  I'm not sure if I have mentioned this before, but I drive a 1990 Honda Civic that is worth probably about $900, so I was starting to think that old "Cupcake" had finally come to the end if its life.  (I didn't name my car, by the way).

As always, I looked into doing the work myself to save money.  The parts from Autozone were only about $100 for a fan motor and all the hoses.  I didn't think that the thermostat would need replacing.  Sure it might be the recommended thing to do (might be), but this is a car that is probably on its last legs anyway.  I'm looking to fix it on the cheap.

Replacing the Radiator Upper Hose
I had noticed that the upper hose seemed to be spraying fluid from a small hole near the hose clamp, so I first set about replacing it.  I never claim to do everything perfectly the first time, and I made the mistake of disconnecting the hose before draining the system.  So the engine drained all of its antifreeze down the engine block and through the car down into my oil change pan.  I probably should have thought of that, but whatever.  I'm throwing it all away anyway.

Draining the  System (as I should have done first)
To drain the system, there is a small plug on the bottom of the radiator accessible from under the car.  It's meant to be easy to find.  On mine, if you unscrew it a little, then a small hole is exposed, and if you continue the whole thing will come out.  You need somewhere for air to come in the system, so make sure you remove the radiator cap.  Also turn the A/C to full heat to open the valve to the heater core.  Mine is actually a valve connected via a cable to the control knob, but it's old as yours may be different.

To remove the cap, turn about a quarter turn counter-clockwise.  Of course the engine should be nice and cool when you do this, so you don't spray hot antifreeze all over yourself.  To remove the cap all the way, push down and continue to turn counter-clockwise.  Then it should pop right off.

On my car there is also an air vent up near where the upper radiator hose connects to the engine.  You'll need this open to fill it later anyway, so you might as well do it now.

Changing the Hose (in the right order)

The upper hose is ridiculously easy to change.  First you loosen the hose clamps with a screwdriver.  No problem there.  Then give the hose a good prolonged pull with a little twisting and working back and forth.  It should pop right off.  You might be able to spray a little WD-40 around the end to try to loosen it up a bit.  I'm not sure if that helped me or not.

After the hose is off, just grab the new one, put the hose clamps on it loosely, shove it on the barbs, and clamp it down.  Make sure you clamp after the little lip on the barb.  No problem.

Refilling the System
I followed the directions in my shop manual pretty closely.  I managed to find it on usenet a long time ago and downloaded it.  You should have taken off the cap for the draining, so you just need to replace the plug in the bottom and start filling the system with a funnel.  Leave the vent by the engine open until antifreeze steadily starts flowing out.  This happened in about the last 2 inches of filling for me.  You need to tighten it back down and then fill the radiator to the bottom of the neck with antifreeze.  Leave the cap off for now.

Also fill the reservoir to the max line with antifreeze.  I found that shining  a flashlight down into the reservoir will make the antifreeze glow a little through the plastic so that you can see the level easily.

Burping the System
Because we just filled an empty system with fluid, there are some pockets of air in there.  If we put the cap on, there wouldn't be a very good place for the air to go, so we leave the cap off and start the car.  Let the car run for a good long while to warm up.  When the car is first started,  all of the coolant just loops around the engine as it warms up.  It doesn't even go through the radiator.  As the coolant begins to warm up with the engine, more is passed through the radiator to begin to take heat away from the engine.  Also, the heated liquid will expand and fill in all the space.  So you want to make sure that the car gets nice and warm for the purpose of getting all the air out.

In my case, quite a bit of antifreeze bubbled out of the open cap from time to time.  I just wrapped it with a shop towel and soaked it up as much as possible.  At first I imagine that this is because the air is pushing the fluid out as it works it way out of the system.  Later, the fluid is actually expanding and contracting due to the temperature changes.  At least that's my theory. 

My manual said to wait until the fan comes on at least twice before replacing the cap.

Drive Around
After replacing the hose and coolant, I did some driving.  To my delight I couldn't get the thing to overheat.  I was very excited, and I thought that I had fixed the whole thing for $20.  Luckily this proved to not be too far from the truth.

Check for Leaks
Here's where I saw my mistake.  I had done fine with the hose I replaced, but it actually wasn't even leaking.  The upper heater core hose was spraying from nearby, and it looked like the stream was coming from the radiator hose.  It seemed that leaving the system in this state would put me right back where I had started in the near future, so I went back out to Autozone and purchased the heater hose (and returned the fan motor).  Another $10.

Changing the Heater Hose
The heater hose is as difficult to change as the upper radiator hose was easy.  It's tucked way the heck under a bunch of crap.  The spark plug wires get in the way.  I felt like I was going to break the heater valve.  And to top it all off, it has those infernal spring clips on it instead of worm clamps.  The only advice I can give you is that there is an easiest angle to get at those clamps.  For me, I ended up hugging the engine so that I couldn't even see the clamp.  I put the pliers on by feel with my other hand.  Actually I do have two other tricks for those things.  First try to grab them with your pliers parallel to the plane of the ring.  That seems to be the easiest way.  Secondly, once you have them squeezed, don't try to move them with the pliers. Use your other hand to gently push them down the hose while maintaining pressure on the pliers.  Otherwise you'll end up cursing, sweating, and shaking from holding the same leaning position for so long (like me).  Once the damned clamps are figured out, it's not too hard to change the hose.  Just keep at it, and try to stay patient.

Finishing Up
I actually had to drain the system a second time to replace the second hose, but I was able to save all the fluid to put back in.  After driving around some more and making sure the clamps were all secure, I have decided that the car is fixed.  The temperature is rock solid where it normally is, and I am very happy.  I was definitely able to see the little hole in the old heater hose that was causing all the problems.

In retrospect, I believe that my whole problem was that I was low on coolant.  The heater hose had been leaking for a while, and I had thought that it was transmission fluid from another previous leaking hose.  But actually, I've been losing coolant for a while now.  I guess it finally got so low that the system couldn't keep the engine cool in traffic.

Also, I have no idea how old that coolant was.  It was pretty nasty looking when compared to the new clean stuff.  I have read that you can flush the system with water in between draining and filling.  Just pump it full of water and drive it or run it for a while.  Then drain it and put the real stuff in.

So for the grand total of $40, I have fixed my car's cooling problem.  $20 in antifreeze and two $10 hoses.  If I'd known exactly what to do, I could have done it for $20, but I'm not too worried about that when the alternative was $800, or more realistically a new car.

If someone has a similar problem, I hope that they see that it might be very simple to fix.  Don't let the mechanic talk you into changing every freaking thing in your car just because one hose has a leak and you're low on coolant.

Thanks for reading,


  1. The hoses carry the coolant from the radiator to the waterpump and from the engine to the radiator. Hoses are generally made of rubber and can deteriorate with time.

  2. Keeping coolant in your car or truck is important to your vehicle's cooling system. Its primary function is to protect your car's engine during times of extreme temperature.