Technical UNO 70sx water leakage / overheating??

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Technical UNO 70sx water leakage / overheating??


New member
Aug 29, 2007
Hi all,

I've had my 1987 uno 70sx for a while now. I had a new gasket in Italy 6 years ago and a new gear box in France 3 years ago. I've also lots of newy bits to keep things happy in the engine bay for such an old but superb car. Now the problem I've had, and it's been their for about 4 years, is that it overheats in even the mildest days and sitting in traffic in winter! The engines been rebuilt when the gasket was changed, I've a new thurmostat, sensor, water pump and a genuine new radiator. The fan now works great (some *** connected the fan to work in reverse so never cooled).

I've long thought that it could be a blocked heater matrix causing the coolant flow not to err flow... In summer the blower also blasts out hot air, cannot get cool air.. Could the Matrix be the problem??? I now also have a leak in the driver side, flooded with green coolant (lovely).

I gues I'm looking at changing the hose leading to the matrix, but it looks like a bugger to get at. Does anyone know if I need to remove the dash completely?? If I do, then should I get a new matrix at the same time??? I want to do this myself, but do not want to go the long way if not required.

Thanks all
Hi and welcome to the Fiat Forum :wave:

We have a Uno section and you'll get a better response if you post in there. I've asked a mod to move this post to that section.

First off, mk1 Uno SX - nice car (y) I've been tempted by a couple lately but missed out on both of them :(

As for your problem, the fact that you have coolant leaking into the footwells means that you have a leak in the cooling system. As the the cooling system needs to be pressurised to raise the boiling point of the coolant, any leaks will cause a pressure loss and lower the boiling point causing it to overheat which is probably what is happening in your case.

If you are still getting hot air from the heater then I doubt if the matrix is blocked. If you can ONLY get hot air then it sounds more like the valve in the matrix is seized. The valve can be changed on its own, or the whole matrix can be changed. Either way, with coolant in the footwells you have a leak that needs dealing with.

There's some debate about whether the matrix can or cannot be removed in situ. I'm fairly certain it can as I'm sure I removed one this way in my old mk1 45 years ago. Problem is it was so long ago I can't quite remember :eek:

It should slide out of the heater box into the driver's footwell. You might have to disconnect the steering column for clearance but then again you might not. Have a lie down in the footwell and look at where the pipes go into the matrix and you'll get an idea as to how it can be removed.

The whole dashboard can be removed and its not as difficult as it sounds. I did mine (twice! Damn incompatible under dash wiring looms :bang:) but it can be a bit time consuming. With the dashboard removed the heater box will still be attached to the bulkhead but you'll have a lot more space to work around.

This thread will give you an idea as to what's involved:

By the way, please post some pics of your Uno as it's always nice to see the increasingly rare mk1 models, especially the SX (y)
Thanks a lot for your advice.

I removed the radiator cover over the long weekend to cut any pressure in the system and stop drips..especially as I could hear the sizzling, see the dripping, but no way see where it was starting from.

This morning it was all dried out and I wiped the valves and pipes down before refilling and going about my business. There was NO dripps and no sizzling, so it looks like it must be the valve on the side of the matrix as that was wiped clean and the warm air moved to the off position. There is also it seems a slight play between the moving the front panel controls to the heater and the actual movement on the valve (by hand I can push it further).

I guess it's better to give the valve the first shot, but can I still get a new valve?? Fiat dealers stopped supplying parts in 2002 and my other contacts have also failed. I'm hoping you going to be good enough to know where I can find one..

An idiot also backed into be a month ago, the dent was repaired and sprayed OK, but in the process they lost the wheel arch trim...which is more difficult to find than am honest word from any politician!! I'm now trawling overseas for this one, single, solitary part..I'm told that perhaps the turbo version will fit..

Thanks again..
I feel your pain! My Uno is a 1986 model, and Fiat's electronic parts catalogue (Eper) only goes back as far as 1988. If I go into any modern Fiat dealer and give them my chassis number they tell me my car doesn't exist... :bang:

You could try a Fiat dealer for the valve, but to be honest I've no idea where you'd get one from otherwise. Maybe a radiator specialist? I have a feeling that the later Pandas and Unos used the same valve so that might be on option worth exploring. Otherwise you are looking at scrapyards and hoping for the best.

I have a spare matrix and valve (in a spare heater box assembly) but for obvious reasons I'm holding on to it!

The wheel arch trims are a little tricky to find, but yes, the turbo (both mk1 and mk2) used the same trims. The skirts on the mk2 turbo are slightly different to mk1's though as some are embossed with 'Turbo i.e.' on them but should still fit.

How about posting some pictures of your Uno? It would be great to see it :)
Hi UnoLover!
Welcome to the Uno forum... (y)

As Chas says, show us some pics, as that sounds like a very well-cared-for and rare Uno!

About the overheating. I don't personally think that a faulty heater could cause the engine to overheat, as the heater is 'in parallel' with the front radiator. Otherwise, if it could cause a lack of circulation, every Uno would overheat when you turned the heater off, since the heater valve is supposed to stop the flow.

It's common for the heater valve to be a little sticky - i.e. not to move the full range of travel - and they don't work very progressively either, even when brand new (the heat tends to be off or ON, with little in between).

It is fairly easy to replace the valve - no need to remove heater or dashboard from the car. Just put a ~10L plastic bowl under the heater and remove the pipes. The valve has a couple of 10mm nuts on studs mounted in plastic - be gentle!

To fix a coolant leak from the heater matrix or hoses (not very common)... you can remove the heater without removing the dashboard (not sure if Chas was aware of this :) - just undo the four nuts at the front bulkhead, underneath the dashboard. Remove the single screw under a square plastic cap on the dashboard top (just in front of the padded 'roll'). And that's about it - though, if your SX model has some type of floor console (I think it does?) then that will have to come out first in order to give space to drop the heater unit.

A short-term solution (while you make time for the above) is to use a 12mm deep-socket (a useless size on a FIAT anyway) to join the two heater pipes together in the engine bay, bypassing the heater. Since I managed this at the side of a road once (without cutting any hoses), I'm sure there's a plastic T-fitting or similar where you can remove the hoses and join them.

Meanwhile, I think your overheating problem is somewhere else. You have replaced all the other possible components, so we have to start thinking of possible component failures.

The first easy answer would be if the alternator/water pump drivebelt were slack - any electrical problems/flat battery? Lately I've seen a couple of belts that were loose but silent. I always thought a loose belt would squeal, but seemingly not if the belt is fairly new.

For example, if the water pump impeller (turbine) becomes loose on the shaft, you can have the problem that you describe. This can happen with even nearly-new parts! I think you should remove the front part of the water pump (loosen alternator, take off drivebelt, and undo four bolts holding pump front casing) and inspect carefully, which shouldn't take long ;) Apologies if I'm being too over-simple for you; I guess you probably know the Uno well by now!

The next suspect would be the thermostat - usually these fail in the 'open' position, but perhaps in this case it has failed 'closed'. Again it is easy to remove the part and inspect - just three nuts, as I'm sure you know.

I presume that (with the heater leak fixed) the coolant level does not drop noticeably - if the level is down a few cm in a month, that's fine, but if the level is dropping to 'empty' in a week, then I suggest that you have (another) head gasket leak - perhaps the cylinder head was not cleaned/resurfaced. But let's treat that as a final possibility. You can usually see signs of air in the cooling system (e.g. coolant 'boiling over' soon after starting) when a head gasket fails, because the combustion pressure tends to pressurise the cooling system (rather than the other way around). Also it is common to get oil in the water or water in the oil.

Anyway, best wishes... and keep us updated (sorry I'm quite busy at the moment so may not see your message for a while - but I will definitely see it eventually ;))


PS. Chas (1986Uno45S) is right about the wheelarch trims (being the same on the Turbo and hence reasonably-available) but I'm pretty certain that the sill trims (the straight parts) are different for the 3-dr vs. the 5-dr. You may be able to cut the 3-dr trim back slightly along the top edge and make it fit.

PS 2. Re-reading your original post, I realise that you probably just need the wheelarch part, so no worries :eek:
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I'm pretty certain that the sill trims (the straight parts) are different for the 3-dr vs. the 5-dr. You may be able to cut the 3-dr trim back slightly along the top edge and make it fit.

According to Jai they are the same ;) When we broke up a 70SX a couple of years ago Jai grabbed the wheel arch trims and sideskirts for his 3 door turbo and wouldn't let them go!

Plus don't forget that the 3 door Uno has the same exterior dimensions as the 5 door, so that means the sills are also the same length! Maybe Jai needs to check the 5 door skirts with his 3 door tub to be sure :chin: