Hi all,

I'm into troubleshooting an overheating issue with my basic 2007 fit...the car has 66k. Here's the problem:

My hot engine light starts flashing after about 15 min of marginal driving on the open road. Outside temp is about 20-25 celcius... When that happens I simply turn the heat on and blower at max and the light stop flashing in less then 30 sec...

Now here's the background...last fall I had to change the rad due to a rock that dig a hole in it...The repair was not done in a dealer and the coolant is not genuine honda... I drove all winter with no problem. The only thing is that I got the sqwooshing sound out of the dash board witch I'm sure is a badly bleed system.( Btw, I bought the car new and I own it for more then 4 years, I'm know that sounds can come form the gaz moving in the tank, but this is not ...)

So... I have attempted to bleed to system by raising the front end of the car and letting it heat up with the radiator cap removed...I did this several times and I still got the sound behind the dash...curiously the car will not overheat even if I let it idle in the sun for 30 min...Also the fan doesn't come on (more on that below)...

After several attemps of bleeding the system, I decided to change the thermostat in case it was faulty and stuck close... I have refill and rebleed the system... The overheating on the open road remains...

There are no leak in the system and fuel milage is good.

Then I suspected the fan to not be turning on to be the issue...I can make the fan run by jumping the relay so I did a test drive with the fan running continuously and the flashing red light came up again...

At this point I'm pretty hopeless...Any help/advise or clue would be greatly appreciated,

Thanks,

 

Have you tried "burping" your coolant system without the front raised?

 

I have always did the procedure with the front raised...
Btw, This morning, the day after my last ride with the fan on has I have describe previously, I inspected the coolant level and it was right at the cap level in the rad and had gone from max to min in the expansion tank... No sqwooshing noise at start up... I tough to my self that I had finnely got rid of the air...went for a 12 km test ride...with a smile on my face until the overheating light started to flash again...

 

Water pump damage?

 

Anyway to trouble shoot the pump without removing it?

 

First, I really doubt if the heater core could make any noise. Air in the system will always work itself out...that's the reason for an overflow tank. The proper procedure for filling is topping off the radiator best you can during a coolant change, and then use the overflow tank. In other words, use the overflow tank for normal coolant checking and fluid levels.

Second, any quality coolant will result in the same cooling...so not using Honda would make no difference. Is it a 50/50 mix?

Third, is the vehicle using coolant? You mentioned that the overflow tank went from max to min...does this happen often? If so, you may have a blown head gasket or some type of coolant leak. Head gasket probably not, since it doesn't seem that you are overheating. Maybe this was just related to a recent coolant change. I did a coolant change on my 09 Fit and the coolant overflow tank dropped only slightly as all the air worked itself out.

Fourth, I wonder if you have a sensor issue. The result being the light coming on with the engine still within normal temp range. If turning on the heater can make the light turn off, then the temp drop does not sound like much. I would probably install a new sensor (which is not a thermostat).

My guess is that you don't have an over heating problem, but rather a bad sensor. As to the dash sound...windshield fluid?? Something in glove box???

 

Thanks for your inputs!

No, the car is not using coolant. The change of level in the expansion tank is the result of when I changed my thermostat and the bleeding exercise that followed. I've been checking my level everyday for the last 2 weeks and it is stable...

I do think the bad sensor make sense. it seams that it would be triggering the dash light at a lower temperature then it should... is that a common sensor failure? would that justify the fact that the fan doesn't start?

 

My suggestion is to have some shop connect a code reader and see what codes come up. I owned a 1987 Ford Bronco II and had s smog-check shop tell me that the vehicle would fail the current smog check in CA. They offered to replace the "faulty" 02 sensor to make it pass the smog check. I said "OK".

Thereafter, the vehicle would constantly bog down and then surge while driving, and would emit a huge cloud of smoke in the "bog" stage. I had three separate shops check it out on their computers, and all they could do was replace the ignition module that Ford attached to the side of the distributor for several years on the Bronco II's and small pickups. The modules infamous for failing at random and causing wrecks all over the country for a decade or so.

So with no answers from professionals, with a broken leg in a cast, I dragged myself under the truck and replaced the "new" 02 sensor that the smog check shop had installed incorrectly. The stock 02 sensor had two leads with black insulation and one lead with white insulation. The smog shop just cut the sensor leads and used crimp connectors to re-attach the new leads. They connected the wrong black leads, and the ECU was getting bad info. from the incorrectly connected 02 sensor leads.

The end result was terrible running conditions, unburned fuel clouds coming from the exhaust, and overheating all the time. After I replaced the 02 sensor CORRECTLY,, the heating and running problems went away.

These conditions are very unlikely to happen in a Fit due to completely different ECU's and smog systems, but an incorrectly installed 02 sensor can produce some really weird symptoms.

 

I don't know, but I had a Ford Aerostar that had a digital dash (it was really cool) and my oil pressure warning digital display and chime went off one time while driving. Turned out that the oil pressure was just fine, but the sensor went bad. Replaced it and never had any other problems. The Fit temp sensor might operate the fan, but not sure. I thought your light only came on while driving...so I'm not sure how you can validate if the fan is running. Nonetheless, I would change out the sensor. If that's not the problem, then I would suspect a coolant flow issue. There might be a way to validate true coolant temp with a real gauge.

Since you forced the fan to run regardless, and the temp light still came on I'm thinking that the engine is not overheating but rather a false indicator. Let us know if changing out the sensor was the answer.

 

i had this problem once..... exactly as you say, with the swooshing sound. the difference is i had a water temp gauge, so i can see the water temp climbing from 78 celcius to over 100 in 60 seconds... and then rev it some more and it go down back to around 84.... before climbing up again... at that point i stopped the car.

And this is why: my heater core was damaged and the coolant leaks into the inside floor. this creates air bubble in the system. when the water circulates, and we get to the part where there's a lot of air bubble passing thorugh the engine, the water temps rises sharply... when circulated and the engine got the full collant running, it drop the temps...

so i would suggest that you check your floor on the driver side and passenger side, whether the carpet is damp. if it is, then you will have to repair the heater core.

If it is all dry and nice, you only have to bleed the radiator. Don't listen to the guy saying the overflow tanks will take care of it. It will not. It is as the name suggests. Overflow tank. When the temp rises and some fluid evaporates, it will be condensed back into fluid inside the overflow tank. when it's getting cold and the pressure of the radiator drops, then it will suck coolant from the overflow tank. It will NOT however eliminate air bubbles trapped inside the system. The reason being the pressure inside the radiator. you need to understand fluid dynamics to fully understand this, and i'm no master of that area... so you need to do research

To cut the story short, if you want to properly bleed the radiator, you don't need to raise your front of the car... but you need to prepare a big pan to contain the coolant overflowing. This is how:
1. with your engine cold and off, fill in the coolant through the radiator until it is full to the brim. Don't forget to fill in the overflow tank too.
2. then run your engine with the radiator cap off.. it will overflow a bit, and if you have air bubbles in the system it will gradually subsided...
3. take notice of the coolant level inside the radiator during all of this... continue to add coolant directly thorugh the radiator cap whenever the coolant level inside drops.
4. from time to time the coolant will overflow from the radiator. this is normal, and this is why you should have a big pan underneath the radiator to contain this overflows. But don't shut off the engine just yet, even if it is overflowing, keep on running the engine... at some point the coolant level will drop again, meaning that it found another air pockets to fill... add the coolant again..
5. continue this until the fan kicks in, and the coolant level never drops anymore. at this point just replace the radiator cap (since the coolant will still overflow). fill in the overflow tank again until it is on max. let it idel for a bit, and you can shut off the engine...
6. wait until the engine is cold again, and check your overflow tank.. fill it in again if it is not on max. by now, you should be free of temperature rising and dropping as well as the swooshing sound..

 

sorry i forgot to remind a small but important bit... make sure that the rubber tube that goes inside your overflow tank is connected properly and can reach the coolant level inside the overflow tank, and your overflow tank cap is not broken or have holes in it.... you might disregard this as small details, but this is actually a vital point in having a fully functional radiator cooling system or a bad one... a bad cap or detached tube will make the radiator unable to suck coolant from the overflow tank when it needs... this in turn will create air bubbles in the system....

the small detail you forgot to mention above is whether after changing the thermostat and rebleeding the system, you still hear swooshing sound or not... if yes... then check your bleeding technique whether it is already as i stated above and do it again just as i post... it may take you up to 20-30 minutes to properly bleed a system depending on your ambient temperature. if you do not hear any swooshing sound, your thermostat is new, your coolant level in the radiator and overflow tank is full, overflow tank is connected properly... then sensor check it is.

 

Actually the radiator, specifically the radiator cap/fill neck is the highest point of a properly designed cooling system, and any air trapped should get to this point. If you look at the cap there are two seals, and the purpose is for air to purge out through the overflow line past the first seal. This will also draw coolant back from the overflow tank during cool-down resulting in a filled system, given that the overflow tube is sealed and running to the bottom of the tank. In 40+ years of performing cooling system maintenance on all my cars and motorcycles I've never had an issue of trapped air. Also, if you read carefully you'll notice that I mentioned to do the initial system topping through the radiator the best you can..and I always run the engine during this process. But it never results in a perfect filled system...but the overflow tank will finish the job. To each his own.

Sounds like any trapped air is out of the system and pulled back any needed coolant...which is how it should. So the issue remains..why does the light come on? Is there a real overheating problem, or is there a defective sensor? Probably a sensor.

That is just not true (well, maybe the very last part is). The caps are designed to allow air to purge, and for small fluid movement to/from the overflow tank. And it does this due to the system pressure...and in order for this to happen, the cooling system temp must be brought up to full operating temps over several cycles. Air will stay trapped if the system is never brought to full temp...which creates the pressure and temp required to expand (and super heat) the trapped air. That air will then purge through the cap and the cool-down will pull fluid back into the radiator. Not really rocket science. The reason there is a "max" level on the tank is in case of higher than normal temps (like stop and go traffic)...which will result in higher volume fluid movement.

 

Sorry, but two other corrections. Although you don't want a "broken" overflow tank cap, you do want one that has a vent hole. That vent allows the tank to accept fluid and allow fluid to return back to the radiator when required. You are correct that the overflow hose must have a good seal on each end, not have any cracks or holes, and that the hose reach the overflow tank at the bottom. Think of it as a straw in a glass of water. If the bottom of the straw doesn't reach the fluid, you can't draw up any water. But yes, the overflow cap must have a vent hole, just like the top of a glass of water is like a giant vent hole....or else the cap will either blow off or the vent line will.

If the overflow tank was to lose fluid (say it developed a crack and leaked) and the system tried to draw fluid during cool-down, then air would be pulled back into the radiator. However, the system will not normally recirculate this air, rather it will stay at the top of the radiator...resulting in a "less than full" system, but not one that would be constantly circulating a mix of fluid and air. At that point you could simply top off the radiator with the correct fluid and replace the overflow tank. You have to understand that your engine (water pump) pulls coolant from the bottom of the radiator..so any air still at the top will never get remixed into the system. Same reason why Shamo the killer whale has to come to the top for another breath of air...air just doesn't want to travel down through fluid.

 

FXfit...make sure that your current radiator cap meets the correct specs, since you mentioned that the radiator was replaced. An incorrect cap can prevent the system from purging the air. If you still have the OEM cap I would use that. Since the overflow tank did change I'm assuming the cap is ok, but just a thought.

 

Spacecoast: i'm not going to argue for most part of your post, since the majority is rightly correct in theory. In a working cooling system, the radiator cap and the overflow tank will take care of any small bubbles, and you would have a perfectly running cooling system.

And let me emphasize that theoritically i agree with you. However in practice, when you already have a screwed out cooling system (the swooshing sound), no matter how long you drive around, the air bubbles simply won't come through to the overflow tank. I know, because i have run for 2 weeks with that swooshing sound, each time checking my radiator is full to the brim, and my overflow tank filled. And just like the OP I tried each time to run the engine, fill in through the radiator cap, wait a while, and when it's start to overflow i close the cap. That never works... That's how i got 2 weeks of swooshing sound in my dashboard. You may mock me for being ridiculous or ilogical, but that's just how it is. I can't explain why my cooling system never be able to get rid of the air bubbles automatically, as i said i'm no master of fluid dynamics. But that's just how it runs for me, until I do the above steps of bleeding the radiator.

I also agree that it MIGHT be the sensors not working correctly that results in the blinking light. That's why in my last post I put a question whether after replacing the thermostat and bleeding the system, the OP still hear swooshing sound or not. If not, then most likely the sensors. But if he still does, in any case sensors or not, he will still need to properly bleed the system...

 

Understand...but I'm wondering if you are not achieving proper temps. You have to get the system up to the right temp...that will expand any air and drive that up to the top point of the system...and the pressure of the system will expell the air. Granted there are some cooling systems (like my Chrysler T&C minivan with rear heat) that the top part of the radiator is not exactly the high point, but I've never had a situation when the front heater core would not fully purge. And yes, during cooling system flushings I also fill from the radiator, topping first, then running the engine and filling. But I don't go through a process that you described. The system should purge. Also I did change the coolant out of our 09 Fit last December (Dec 2011)...didn't run into any issues thankfully. It did pull down a slight amount of coolant from the tank over a two/three day cycle period...but not too much and of course its stable now.

 

Are you remembering to set the temperature control dial to full hot?

 

previous 2008 fit owner....
i had the "waterfall" in my dash for about 2 years.
burped the system a few times using the proper tools (Lisle radiator funnel), never got rid of the sound, but i also never overheated.
over time i would notice that my coolant reservoir was low once and a while (besides the normal fluxuation in level from hot vs cold), id fill it to the proper level...eventually the waterfall sound went away.

unfortunatly, the fits coolant system is not properly designed...the radiator cap is not the highest point of the system. the heater core in teh dash is at a higher level.

with that said...air in the system can cause you to overheat. so try to fix that first. but in my experience, the fits coolant system is a HUGE pita to bleed 100%.

you should also replace the radiator cap for peice of mind. its a cheap part.

the best results i got from burping the system was using the lisle funnel, front of the car on jack stands, heat on hot and highest fan setting, and fill the funnel at least 50% with coolant. this will then be the highest point fo the coolant system). let the car run for a while...at least half our to cycle the fan numerous times. check to make sure the funnel never runs dry (id hope it woulndt as it holds alot of coolant).
hopefully this at least prevents over heating.

 

Ok, Here are the latest developments...

I have changed the engine temp sensor... Re-bleed the system (again)... Went for a ride on a open road and my dashboard light started flashing again...
I'm back at the starting point...
While I was bleeding the system the fan didn't start just like with the original temp sensor...
What's next? a blown head gasket? @ 66000 km? a damage water pump?

here's a recap:

Rad is new from last fall
Thermostat is new
temp sensor is new
No signs of coolant leakage
oil level is perfect
Fuel mileage is good
Rad fan never start unless I manually activate the relay switch
Owner is very sad...

Thanks in advance for helping me looking at other possibility...

 

Humm....I don't think I would worry about a blown head gasket if you don't see bubbles in the coolant. That type of problem will certainly push pressure into the system (hence the bubbles), result in coolant loss and overheating. When the light comes on...are you driving? Does the system actually pressurize? In other words, do the hoses expand and get hard? Any differences since the sensor was changed out? Did you try and manually run the fan to see if that prevents the light from coming on? I guess I'm trying to determine if you really have an over-heating temp issue, or still a false indicator. Also, do you know what kicks the fan on, like perhaps a different sensor located in the radiator? Sorry, but I'm somewhat at a loss as to why this is going on. I would consider installing a true temp gauge if thats possible. Other than that I'm wondering if there is a coolant flow issue...sometimes a good Honda parts manager may know if the pump can fail to move coolant (usually the water pumps fail due to a seal, but they still pump).