Heater is lacklustre

Hello everyone & happy new year,

I'm having a bit of bother with my heater. All the blowers in the cab work fine, I just don't get much heat.

I removed the pipes and blasted some water/flush through the heater core thinking it was a bit gunked up, but everything was clean when it came out. Despite the coolant being clear, when I plumbed it all back up it was very warm - which was fantastic and I thought I had fixed it. I thought there might have been an air pocket in the heater core. 

It's been about a week now and it's progressively got colder again to the point where I can't clear windows well. The engine temperate reads normal (needle is sat happily at halfway as I would expect). There are no leaks anywhere, so the coolant doesn't appear to be getting out. 

Could this be a thermostat issue? If anyone has any other thoughts this would be great. G13b Engine (1999 Jimny).

Thermostat would seem a good place to start to fix your problem.

If the motor is getting up to temperature in a reasonable time frame and holding that temperature over time then it suggests that the thermostat is likely doing its job. You are certain it's not displacing or consuming coolant? When my last one decided to eat it's head gasket I replaced virtually all the cooling system chasing progressively worsening symptoms for nearly 3 years. I would strongly recommend having a meaningful inspection with a competent mechanic, it would have saved me a lot of work.

I think Lambert is right you are loosing coolant somewhere. If the thermostat is sticking open your Jimny wouldn't get up to temperature very quickly or even at all.

Also after flushing the heater matrix, it was OK for a while, this suggests that the water level is dropping in the heater and this would suggest coolant loss. It might be a leak in the heater matrix, you might not even see it if it is small and the water [vapour] has gone in to the hot air, or the leak only occurs at higher engine temperature and drops on to something very hot

If it is your cylinder head/gasket check.....

- the water for oil
- the oil for emulsified deposits
- the spark plugs, to see if one is washed clean.

If that all looks good the leak is most likely somewhere else.

May seem too simple but have you checked the little white coupling by the clutch pedal . Has the cable disconnected and stuck on cold location? That was my issue.

Thanks all for the suggestions. 

Fossie - Yes. This was the first thing I checked and it is still attached and seemed to move the dials correctly when I played with it.

I've gone with a simple fix for starters with hope that a new inexpensive Suzuki-supplied thermostat will fix it. 

Firstly started with draining the radiator a bit, then off with the top hose. Housing came loose quite easily (I was expecting a bit of a struggle). Once it was off and drained again, I started to give it a clean-up and then templated a gasket on some gasket paper. 
 
 

I removed and cleaned up the temperature sensor just in case that was reading incorrectly.
 

Fitted a new pipe that goes to/from the heater matrix as it looked a bit cruddy. New thermostat in with gasket and a tiny bit of gasket sealant for good measure.
 

Early signs seem positive with no leaks and I've got heat. But for how long? Who knows. I'll update this thread with the results either way in a week or so. Then I'll see what else is going on and delve a bit deeper (re: Robin's comment). 



 

Did you fix this in the end?

Hello DJ20, yes it's all fixed and extremely warm now

I don't think the thermostat was the problem in the end. Putting an airline through the heater core along with high-pressure water to remove what appeared to be a load of limescale really did help though. I had little white rocks coming out!

Great news, well done.