MX5Ireland

Hi folks!

I haven't been on here much but am hoping to get more involved over the next while. I recently picked up a 92 1.6 and it is in pretty good nick, but like them all needs a few jobs done. The first job I tried to tackle today was what I presumed was a dodgy thermostat. Symptoms are a heater that doesn't like to heat and the car takes ages to heat up. it never gets fully up to temperature. I replaced the 'stat today, but it doesn't seem to have made any difference.

Any ideas where to look next?

How cold is it outside :p

I always find it takes an age for my cars to heat up when its this cold

What I have done before with older cars was use Fiat/Alfa thermostat because they always ran a bit hotter ie maybe 88degrees rather standard 78/82 degree type It certainly won't do any damage either way in the Irish climate.JUst make sure it is correct size diameter etc

Sorry forgot to add maybe heater rad under dash is blocked ?? Or waterpump impellar worn/damaged and not pushing water around fast enough but unlikely on mx5.Check temperature of heater hoses in engine bay going in to cabin area.

What is gauge reading??? Cold??? Reason i ask is because our yoke is the same. Has aircon but its all removed bar the evaporator thingy under the dash. Problem is, cold air is being blown by the fan into the cabin before it goes into heater matrix.
Check under your dash for badly seated trunking to heater if, all else with the engine is ok.
Do remember tho, an engine without a thermostat or one that doesn't work will wear out very quickly.

Thanks for the input folks. I won't get a chance to get near it for a week or so but I'll report back when I get at it again.

*heater hoses under dash - I don't have the car here to check, but one of them was definitely pretty hot, the other much cooler.

*temp gauge gets about 1/3rd of the way up and that's where it stays. If I leave the heater off, it seems to build up heat so will be warm for a short while and then cool the longer it is left on. Until this is sorted the car will not be in regular use so I'm not worried about engine damage

have you checked the coolant level in the rad itself (not the expansion tank)?

yep, I filled it through the rad and then checked the expansion tank after so that shouldn't be the problem...

I just double checked the old 'stat I removed and it's working perfectly so that wasn't the problem...it'll require a bit more investigation I think!

Tried leaving it idle on a slope with rad cap off for a bit to bleed it?

And heater on full and hot on car to ensure water circulates...

I'll get a chance to make sure it's bled during the week so that will rule that out. I was up at it last week and started it from cold. As far as I can see, the heating system is doing it's job as far as the heater hoses that connect in under the dash. they were the first to heat up and were plenty warm. If I don't turn the heater on, it will build up heat, so if I turn the heater on at that stage it will be hot for a few seconds and then cool.

I'm starting to think it'll have to be a dash out job for further investigation but I won't get time to do that for a few weeks yet

take out the glove-box lid.......a pair of screws and turn the fan on full. See is it blowing out air from the joints before it goes thro the heater .
The fan unit is on passenger side, then aircon unit(if fitted) then heater unit in centre of dash.. If there is no air-con there will be a plastic pipe joining fan to heater.

Either way there are 2 joints where air can be blown in by the fan before it gets heated.

sidewaysreilly wrote:take out the glove-box lid.......a pair of screws and turn the fan on full. See is it blowing out air from the joints before it goes thro the heater .
The fan unit is on passenger side, then aircon unit(if fitted) then heater unit in centre of dash.. If there is no air-con there will be a plastic pipe joining fan to heater.

Either way there are 2 joints where air can be blown in by the fan before it gets heated.

full marks that man!

I just got a chance to look at it there, bled the system properly (there were a few air bubbles alright so that probably didn't help). Took the glovebox off and there was air escaping everywhere from the join into the aircon unit. They don't seem to line up correctly but the large clip surrounding the join was really loose. I didn't actually have time to fix it today but at least now I know where the leak is and will be able to sort it easily after Christmas. Thanks for the help folks!

For reference I took a few pictures so here is the join with the clip on (you can see it is quite loose)


and here is the clip off


Hopefully it should just need a bit of duct tape, or some other sealant and all will be well

Thats it, i just got some double sided rubber tape. Dont know where you get it(we use it at work to seal compartments) but duct tape will do rightly if you can get it right around the perimeter of the joint.I stuck the tape to the clamps and it did the trick. Great to have heat again.
You may get it in hardware stores or ebay or????????