Heater blowing cold?

[Mr MXT]

After the cold spell, my bloody heater is refusing to live up to the promise of its name. Eventually I can get a tiny little bit of lukewarm air, but not enough to make any meaningful warmth.

I've not had a recent coolant change or anything similar. I've checked the cooling system for airlocks, ran it with the cap off and the front jacked up as best as I can. I've popped the hoses off the heater matrix and flushed it through with a garden hose.

Still no warmth - I'm out of ideas??

(I'm sure its irrelavant but i do have an uprated "performance" rad - its not new though and Im sure i've had heat since its been fitted months ago. Car takes no longer to warm up than usual).

Help! I'm bloody freezing!

[MX-5 Lazza]

Try fitting a new thermostat. Sounds like it might be stuck open.

[Mr MXT]

MX-5 Lazza said:

Try fitting a new thermostat. Sounds like it might be stuck open.

Cheers mate, but I'm pretty sure its not something nice and easy like the stat

I fitted a new stat in June
Water temp takes no longer to warm up than normal
Rad top hose "suddenly" gets hot rather than gradually warming up, suggesting that the stat has just opened

[mad4amanda]

Does the rad have cold spots across it or up down ? If so a blocked rad is slowing the progress around the system , Mx5 rads block really easily esp on early cars reducing an otherwise good rad to scrap. Alternatively the heater matrix can be blocked by crud remove both heater pipes and flush until a good volume of water comes out clean. Finally check heater control cables not jammed or plastic broken on levers as they get brittle when old/cold .
Hope this helps

[Mr MXT]

mad4amanda said:

Does the rad have cold spots across it or up down ? If so a blocked rad is slowing the progress around the system , Mx5 rads block really easily esp on early cars reducing an otherwise good rad to scrap. Alternatively the heater matrix can be blocked by crud remove both heater pipes and flush until a good volume of water comes out clean. Finally check heater control cables not jammed or plastic broken on levers as they get brittle when old/cold .
Hope this helps

Rad was new in June and I flushed the heater matrix out on Saturday

[NeoVR]

Check the coolant level and if possible raise the front end of the car and take the rad cap off, warm the engine up to check for airlock

If the level is low or theres airlock its usually at the heater matrix.
when i had a leaky rad, the heater not working was the first sign of needing to top-up