Technical uno heater problem

[arvinleigh]

hi. i've had a problem with the heater of my uno (not heating at all)

found out the heater radiator itself was at falt as it was blocked with dirt. replaced it at still it didnt work. this time it was due to a low flow into the heater radiator.
i guess the problem lies from under the carburator as shown in the pics below

the outlet of coolant from there to the heater is quite small and poking my finger in there it seems that there is some dirt which cant me removed easly.

i was thinking of removing the whole bit and cleaning it.. my only concern is that due to this piece having the carburator etc attached to it tha by removing it it might cause some problmes with the engine... any clue??

it seems quite a straith forward job to remove it but i dont know what lies underneath.. any help??? thanks

 

[alexGS]

Hello, welcome to the forum :wave:

Have you checked the thermostat? I see it's a FIRE - many FIRE-engine Unos (in NZ at least) don't have temperature gauges (I think in England, most do). Without a temperature gauge, it's difficult to tell if the engine is reaching an adequate temperature (should be about halfway up the gauge).

It is easy to take the thermostat off (under the distributor, only two 13mm nuts) and inspect to see if it is closing - they usually fail in the open position. There will be very little heat from the heater if a FIRE engine has a stuck-open thermostat and the ambient temperature is below 20 degrees C.

Another common problem is an airlock in the heater pipes - since they are at the highest point in the cooling system, air tends to collect there. Many versions have a bleed screw to help with getting the air out (remove screw with engine running).

The water valve on the heater radiator often fails and I have found this is often the root cause of the heater silting up due to poor flow. The valve may either seize or its operating arm loses the ability to rotate the disc valve (or move the slide valve, depending on design). So don't assume the valve is opening just because the operating arm is moving Again it's worth taking off to inspect (right side of heater, two 10mm nuts) if you haven't already done so. Needs a drain pan in the footwell to catch about 500mL.

Sorry to throw three more possibilities at you! It's just I can't quite understand which part you were asking about... why does the inlet manifold have to come off?

Nice hose clips, by the way!

-Alex

 

[a73uk]

Dont assume the dash dials are connected properly either, they have virtually the same `feel` whether they are connected or not, you have to get someone to turn the dial while your watching the valve in the engine bay to make sure its opening & closing.

As Alex says, its quite likely to be the engine thermostat though.

You`d do well to make a cold air box for that filter as well!

 

[arvinleigh]

the temperature is fine as mine has the temperature gauge.. the thermostat is fine as i've changed it not to long ago. I've removed the intake manifold as thats the only thing which i hadn;t removed and cleaned from the cooling system.. (coolant pases from int intake manifold to the heater pipes) and now after cleainining it the heater is working fine.. now all of a sudden it stopped working and a strange fizzing sound is coming from the heater when the engine stops running.. i think there is air in the heater pipes

 

[Chas Uno]

Fizzing or hissing noises is almost certainly air in the system, or air entering/ escaping the system. Check for any leaks and also check that the coolant level in the radiator isn't falling. Are there any signs of leaks inside the car under the heater matrix?

 

[alexGS]

Dont assume the dash dials are connected properly either, they have virtually the same `feel` whether they are connected or not, you have to get someone to turn the dial while your watching the valve in the engine bay to make sure its opening & closing.

Good point BUT I'm almost 100% certain the valve is not in the engine bay - I think it is under the dash on the end of the heater box (on the Mk2, remove the footwell trim below the steering column that also forms the footrest).

Meanwhile, as Chas says, there is still some air in the heater. Disconnect the upper heater hose or at least loosen it, with the engine running, and refit it while coolant is flowing out - that should bleed the air from the system.

-Alex

 

[arvinleigh]

thanks for all your help.. yes there is a leak.. its from the heater rubber seal.. i wounder if sealer will solve the problem as I dont wish to go through the hassle of removing the heater matrix again

 

[arvinleigh]

i have a leak in the heater matrix.. were the valve is situated which is controlled by the hot / cold nob. there is a leak between the plastic and its rubber seal.. nothing major but its causing air to flow into the system i.e heater not working and also some flouid to come out. Which is the best solution? apart from changing the whole lot? would sealer help?

 

[alexGS]

Yes, silicone sealer may well be sufficient - dry it carefully first, then remove the valve and 'glue' it on with the silicone, do up the nuts and leave it at least a day for the silicone to set...

It's not a common problem though, so it may be best to find a heater matrix out of a stripped Uno (I'm sure some members on here will have one, hopefully if they see this they will offer it...) - as far as I know, the matrix and valve from any Uno will fit any Uno (Mk1 and Mk2 being the same).

Silicone is probably worth a go given that it's cheap and easy to do, though working with your head in the footwell isn't the most comfortable! The matrix slides out of the heater box fairly easily if you unscrew the end cover (two screws).

-Alex

 

[Ucof]

...though working with your head in the footwell isn't the most comfortable!

He isn't wrong.

It's horrible.
I found that laying on your back, with the driver seat fully reclined, and back as far as it will go, with you feet round the back of the headrest to stop yourself from falling into the footwell, looking up into the dashboard, is the most confortable way of doing this.

Please note: I said most comfortable way - i.e - "the least painful".
There is NO comfortable way.

The above way works for me as I am short, and skinny-ish.


Might be worth removing the seat entirely if you can be bothered

 

[arvinleigh]

i will give it a try as the leak is so small that its not worth changing the matrix.

bdw here are some pics of my uno

https://www.fiatforum.com/members-motors/210537-my-uno-mk2.html?p=2248450