Honda City Overheat

[JaiMaai]

My trusty old Honda City (approx. 14 years old/190,000 km) has recently started to show overheating issues after sustained use.  It first showed the problem coming up the hill in Wang Nam Kiaow (so quite a lot of stress), However, after waiting around 20-30 minutes for the engine to cool down, I drove the car for another 350 km (not continuously) without any issues.  The car was then driven on an extended trip again and the warning light came on after around 150 km. I wasn't driving at the time but based on what my partner told me, the engine wasn't under any particular stress at the time.

 

From what I understand there are a few possibilities:

 

1: Insufficient coolant.

I don't believe this is the case because the levels in the expansion tank are midway between the max and min marks.

 

2: Water pump:

  If this was the issue, the problem would show up more often?

 

3: Radiator:  

Don't really know how to check this other than there is no obvious coolant leak.  Could it just be old and clogged?

 

4:  Fan/sensor to turn the fan on

How often should the fan run?  I don't know how to check this.  Should it come on after the car has been sitting idling for a while?

 

5: Any more?

 

One possibly important issue is the coolant was changed recently—just before the big trip where the issue manifested itself.  Could this be related?  I can't easily tell because the car is only ever normally used for fairly short trips.

 

Any thoughts appreciated...

 

Thanks,

 

Jaimaai

 

 

 

 

[In the jungle]

I think the most likely explanation is that whoever changed the coolant did not bleed air out of the system after filling it.

 

If that is the case it will be an easy and inexpensive fix.

[Rickyoz]

Faulty thermostat is another possibility. Anyway, looks like a trip to a mechanic is warranted if not low coolant because air was not bled off.

[hansombeast]

I had  similar issue on m old isuzu pick up, it was a clogged radiator all gunged up restricted flow, radiator was cheap to replace

[JaiMaai]

19 minutes ago, In the jungle said:

I think the most likely explanation is that whoever changed the coolant did not bleed air out of the system after filling it.

 

If that is the case it will be an easy and inexpensive fix.

This makes sense.

 

I think it's too much of a coincidence that the problem occurred right after the coolant change.

[In the jungle]

8 minutes ago, JaiMaai said:

This makes sense.

 

I think it's too much of a coincidence that the problem occurred right after the coolant change.

The bleeding process varies from car to car but I would guess a Honda City falls into the easy category.  Some cars have bleed valves in the system specifically for bleeding air in the coolant.  Whatever the process it would be detailed in the factory service manual.

[brianthainess]

2 hours ago, JaiMaai said:

Fan/sensor to turn the fan on

How often should the fan run?  I don't know how to check this.  Should it come on after the car has been sitting idling for a while?

It could well be the fan motor, its sensor, or its relay. when the temp reaches normal or slightly above the fan should run, it should also run when you first turn on A/C.    When the car is cold, remove the rad cap, to see if it is full, run a while with cap off if your worried about air locks, you can normally see the coolant circulating .Water pumps normaly leak when nackered.

just to add, i once brought a fan motor from Nissan lasted only 15k klm 6k baht ! Brought an after sales motor from GT battery shop still works after 3yrs 2k baht. 

Edited October 25, 2022 by brianthainess

[JaiMaai]

27 minutes ago, brianthainess said:

It could well be the fan motor, its sensor, or its relay. when the temp reaches normal or slightly above the fan should run, it should also run when you first turn on A/C.    When the car is cold, remove the rad cap, to see if it is full, run a while with cap off if your worried about air locks, you can normally see the coolant circulating .Water pumps normaly leak when nackered.

just to add, i once brought a fan motor from Nissan lasted only 15k klm 6k baht ! Brought an after sales motor from GT battery shop still works after 3yrs 2k baht. 

Thanks for this info.

 

I don't think the fan (There are actually 2 fans) is kicking in.  But if the fan was the problem would the engine not overheat quite quickly at idle because there is no airflow through the radiator?

[Lacessit]

How does the OP know what is in the radiator now is the correct coolant? Excessive dilution of coolant or substitution of plain water is a possibility.

The OP should also feel around at the top of the radiator ( inside ) for irregularities such as aggregated rust which should not be there.

I agree with other posters overheating after a coolant change is suspicious.

I'm not sure how coolant gets air in it, being at about 90-110 C in operation. Standard laboratory procedure to degas water is to boil it. Perhaps people floating that hypothesis are confusing engine coolant with brake fluid.

[Lacessit]

28 minutes ago, JaiMaai said:

Thanks for this info.

 

I don't think the fan (There are actually 2 fans) is kicking in.  But if the fan was the problem would the engine not overheat quite quickly at idle because there is no airflow through the radiator?

Yes. The fan is intended to kick in when there is no air flow, such as being stopped at a traffic light.

[In the jungle]

28 minutes ago, Lacessit said:

How does the OP know what is in the radiator now is the correct coolant? Excessive dilution of coolant or substitution of plain water is a possibility.

The OP should also feel around at the top of the radiator ( inside ) for irregularities such as aggregated rust which should not be there.

I agree with other posters overheating after a coolant change is suspicious.

I'm not sure how coolant gets air in it, being at about 90-110 C in operation. Standard laboratory procedure to degas water is to boil it. Perhaps people floating that hypothesis are confusing engine coolant with brake fluid.

Air gets into the system when the old coolant is drained out.

 

That air is normally displaced when you refill the cooling system but it is quite common that not all the air is displaced.  Hence the provision on some cars of coolant system bleeding points.  On other cars a specific refilling process will be described in the factory service manual to get rid of air pockets.  Where such a process is set out it should be invariably followed.

 

On some cars, particularly mid and rear engined cars, the bleeding process involves raising the front of the car higher than the rear.  Of course a Honda City does not fall into that category.

[JaiMaai]

1 hour ago, Lacessit said:

How does the OP know what is in the radiator now is the correct coolant? Excessive dilution of coolant or substitution of plain water is a possibility.

Simple answer is I can't.

 

Even if I took a photo of the bottle they gave me with the excess, I would still be difficult to know if they diluted it correctly. (there is green fluid so there is coolant in the reservoir). Maybe I should just take it somewhere else and get the coolant completely changed again.

[Lacessit]

3 minutes ago, JaiMaai said:

Simple answer is I can't.

 

Even if I took a photo of the bottle they gave me with the excess, I would still be difficult to know if they diluted it correctly. (there is green fluid so there is coolant in the reservoir). Maybe I should just take it somewhere else and get the coolant completely changed again.

Or change it yourself with the correct mix, it's not rocket science.

A couple of other possibilities - a faulty temperature gauge or warning light, or a clogged radiator front if it drove through a swarm of insects. I'm guessing you've probably checked that already.

[Lacessit]

41 minutes ago, In the jungle said:

Air gets into the system when the old coolant is drained out.

 

That air is normally displaced when you refill the cooling system but it is quite common that not all the air is displaced.  Hence the provision on some cars of coolant system bleeding points.  On other cars a specific refilling process will be described in the factory service manual to get rid of air pockets.  Where such a process is set out it should be invariably followed.

 

On some cars, particularly mid and rear engined cars, the bleeding process involves raising the front of the car higher than the rear.  Of course a Honda City does not fall into that category.

I've never heard of air in coolant. The water/coolant pump circulates through the engine block and radiator pretty fast, it has to for heat transfer. Hence any air pocket should disappear quickly.

While I realise air is a very poor transfer medium, it does strain belief so much air would get into the coolant that it would interfere with the coolant's function.

I agree - always follow the manual.

 

 

[JaiMaai]

Thanks for all the feedback.

 

I won't have time to do much until the weekend, but I'll dry bleeding the system again myself and then take the car on a test run.  If it overheats again then I'll take it somewhere else to change the coolant completely again.

[steve187]

21 hours ago, JaiMaai said:

Thanks for this info.

 

I don't think the fan (There are actually 2 fans) is kicking in.  But if the fan was the problem would the engine not overheat quite quickly at idle because there is no airflow through the radiator?

run the car while stationary see if the fan/fans cut in 

[MajorTom]

On 10/25/2022 at 10:33 AM, JaiMaai said:

Thanks for this info.

 

I don't think the fan (There are actually 2 fans) is kicking in.  But if the fan was the problem would the engine not overheat quite quickly at idle because there is no airflow through the radiator?

The fans should start about immediately if you start the car idle with AC on. If not, you have a problem either with fan motors or temperature switch.

I replaced both my fans recently after the wife submerged the car in water.. They were sort of still running but at a very low speed/erratic. Motors were damaged.

 

Engine will not overheat so quickly if you have a fan failure. There is still circulation of coolant. With a pump failure or air pockets however it will happen very fast.

[JaiMaai]

6 minutes ago, MajorTom said:

The fans should start about immediately if you start the car idle with AC on. If not, you have a problem either with fan motors or temperature switch.

I replaced both my fans recently after the wife submerged the car in water.. They were sort of still running but at a very low speed/erratic. Motors were damaged.

 

Engine will not overheat so quickly if you have a fan failure. There is still circulation of coolant. With a pump failure or air pockets however it will happen very fast.

Thanks for this info.  I'll check it out properly when I have time later.

[DaRoadrunner]

On 10/25/2022 at 9:11 AM, In the jungle said:

I think the most likely explanation is that whoever changed the coolant did not bleed air out of the system after filling it.

 

If that is the case it will be an easy and inexpensive fix.

"One possibly important issue is the coolant was changed recently"

 

Yep, possible air lock preventing normal water circulation.