Coolant / overheating problem

[bxcfilm]

My Jazz has started using a lot of coolant. Also, the overheat light comes on too easily. For instance, this morning I drove 8 miles and then sat at a couple of traffic lights for a minuite or two, and the light came on. I'm not sure if the engine is actually overheating - there's no smell.

My garage hasn't identified anything wrong, but they're not Honda specialists...

I would appreciate any ideas.

[culzean]

A garage does not need to be a Honda specialist to diagnose coolant loss. It is either an external leak ( from radiator or a hose or heater radiator, but if it was heater you would have coolant inside the cabin ) or an internal one ( crack in block or head or a blown head gasket ).  Oil in coolant or water in oil ( oil like mayonnaise )   or steam / white vapour  from exhaust are signs of a gasket

[JazzyB]

Have you checked for leaks/level etc

Have a good look all round the engine top to bottom checking all hoses.

Never had any problems with the coolant other than checking the level regularly.

[MartinJG]

I think many of us wonder why Honda have not fitted a simple temp gauge and seem have taken the view of 'trust us'. In my view, it's one of the more important bits of kit in the cockpit. I feel semi blindfolded without one. It can tell us a lot about how the engine is running. Even my old Mini had one all those years ago and believe me, it was needed!

[bus_ter]

If you use an OBDII reader, even a £5 Bluetooth version you can monitor the engine coolant temperature.

My car does not use any coolant, and I've never once seen the overheat light come on. I even struggle to make the fan turn on which requires idling stationary for maybe 15 minutes (I did this following a coolant change and the instructions suggested following this procedure.)

If you're losing noticeable amounts of coolant in a short period you must have a leak. Check the oil to see if it's going there, and carefully around the radiator and hoses. I once used 'radweld' successfully on a car with a leak from the radiator from impact damage. I meant to use it as a temporary solution until replacing the radiator, but after a couple years it was still solid and I sold the car. 

[Jocko]

My ScanGauge (OBD connected) displays the temperature. Even queuing in slow moving, summer traffic has never brought my fan on. Maximum temperature ever reached has been 93°C. For all I know the fan could be broke!

[bxcfilm]

Thanks to everyone for your replies.

If you use an OBDII reader, even a £5 Bluetooth version you can monitor the engine coolant temperature.

Do you mean something like this https://www.amazon.co.uk/Torque-Pro-Elm-327-Bluetooth/dp/B01AC7I7BO/? I must admit I haven't come across that before.

The consensus seems to be that I will have to look harder for a leak. The car was serviced by the garage last month, and they said nothing about the oil. And while there are a few marks on my driveway, they don't add up to an awful lot. And if I arrive with the overheat light on and lift the bonnet, the engine doesn't seem excessively hot.

And last month also, I drove North Kent - Sheffield and back with no issues. If I have to stand in traffic, there can be a problem.

This thing with engine codes makes me mention another issue, which might or might not be related. Last year I had to have a replacement complete exhaust including the cat. It was done by my normal garage, and of course the cat wasn't a Honda one. I managed to have a quick chat at the time with the service manager of my local Honda dealer, and he said that an aftermarket cat would mess with the engine management light. He wasn't wrong.

The light tends to come on if I sit in traffic or have to drive slowly, and it can take a few days for it to go off again. Driving at say 50 mph+ gets rid of it sooner. And last summer I drove up to the Tan Hill Inn (North Pennines - highest inn in England); so of course there's a lot of downhill driving when you leave. That brought the EML on as well.

[Jocko]

If the light doesn't go off when the car cools down, then the fault is the sensor. Is it just the light that is the problem or do you lose water and have to constantly keep topping up?
Regarding the cat. Your Honda Service manager was talking BS. I had a 3rd party cat fitted, garage refitted the sensors, and that was that. EML light has not come on, and it has passed MOT emission tests with no problems.

I just noticed you say you are losing coolant. If the thermostat fails to open then the engine will overheat.

https://www.ebay.co.uk/itm/Replacement-Thermostat-Mitsubishi-Shogun-Iveco-Daily-Honda-Civic-Jazz/303087067334?hash=item469165a0c6:g:uPkAAOSwea5cgBnb&frcectupt=true

[sparky Paul]

Thanks to everyone for your replies.

If you use an OBDII reader, even a £5 Bluetooth version you can monitor the engine coolant temperature.

Do you mean something like this https://www.amazon.co.uk/Torque-Pro-Elm-327-Bluetooth/dp/B01AC7I7BO/? I must admit I haven't come across that before.

That's the sort of thing. You can find them on ebay for under £4 delivered from UK sellers, about £2.50 if you can wait for it to come from China.

www.ebay.co.uk/itm/Mini-ELM327-OBD2-II-Bluetooth-Car-Auto-Diagnostic-Interface-Scanner-NU/143134224089


The coolant has to be going somewhere, and most options have been covered previously. Any half decent garage should be able to identify signs of cracked head or block, or head gasket failure, but I can't say that I've ever come across any of them on here in a couple of years, so they can't be that common on the Jazz.

Most likely is a small leak somewhere - rad, heater matrix, pipework, so that's where I start.

For leaks, look for any signs of white staining on any of the cooling system hoses, particularly around the rad cap and expansion bottle cap.

Also, get the engine and rad good and hot on a cool morning, and have a good look around the radiator and hoses with a torch, looking carefully for any wisps of steam, or even damp patches.

Any trouble demisting? Sometimes points to heater matrix.

Engine overheating can boil coolant through the expansion bottle, but a faulty radiator cap can cause the same problem. On these cars with non-pressurised expansion bottles, it can sometimes be difficult to spot - if you can't find any other cause, just replace the rad cap to rule it out.

[bus_ter]

Thanks to everyone for your replies.

If you use an OBDII reader, even a £5 Bluetooth version you can monitor the engine coolant temperature.

Do you mean something like this https://www.amazon.co.uk/Torque-Pro-Elm-327-Bluetooth/dp/B01AC7I7BO/? I must admit I haven't come across that before.

Yes just like that and mentioned above. Using an app on your phone (Torque Pro being the main one) you can monitor sensors such as the water temperature. You can also read fault codes (so you know exactly what caused the CEL to come on) and reset them. Useful little gadget to own.

[bus_ter]

My ScanGauge (OBD connected) displays the temperature. Even queuing in slow moving, summer traffic has never brought my fan on. Maximum temperature ever reached has been 93°C. For all I know the fan could be broke!

When I did a coolant change I ran the engine with an OBD reader monitoring the temperature until the fan came on. It was actually 93C when it came on. It was quite loud and obvious and quickly dropped the temperature. I think it was a good 15-20mins idling on a Summer's day before it hit this temperature.

[bxcfilm]

Regarding the cat. Your Honda Service manager was talking BS.

Interesting. Your experience was different to mine. Anyway, I have ordered the Torque Pro gadget and I will get the app, and then - as they say - we'll see.

Many thanks to all again.