Hi all.
I've been searching some pictures and/or guides for heater core replacement for my Fiat Stilo 1.4 MY 2004.

Core aint leaking or nothng, but car aint warm enought for northern hemisphere winter. Thermostat is new and working as it should etc. This is just "the last possible option" that i wont do if not neccesary, but it's good to know how it's done if i don't figure anything else that would help with this problem.

Why i'm imagin that heater core could be the issue? At some point at the life of this stilo, someone used to seal a leakage at water pump pipe with some radiator-cement. These are terrible fixes because they could clog up the radiator or heater core in the way that they wont work properly anymore.

Last car, Fiat Bravo 1.2 1999 i had this same issue and replacing a perfecly fine heater core fixed the issue.

Not looking like a '5 minute' job..

https://www.fiatforum.com/stilo/333650-replacing-heater-matrix.html?333650=#post3320978


AFAIK these are not 'throttled'.. they have full flow of coolant by design.. and its the airflow that is controlling the heat

Check the 2 hoses get HOT..and stay like it.. ( showing flow through the matrix)

Beyond that check airflow is correct


This is the 1st of the 150 stilo matrix threads the forums excellent SEARCH found..

Old.. but relevant

Was the thermostat a genuine part or cheaper pattern part?

How do you know it’s working correctly? Does the car get up to temp and then sit bang in the middle of the temp gauge without fluctuation

Ok so heater matrix is same kind of pain in the ass as with Fiat Punto mk2. I have to consider that job a little bit before ordering heater core.

Thermostat was walbro genuine so it should be ok.
But today i will check engine temperature with multiecuscan. Temp gauge rises to top dead center (middle of the rating) and stays there if i dont want to have warm inside the cabin.

Yesterday i drove 120km on highway. I blocked radiator with cardboard "just in case" if that helps. Did not help, still pretty cold inside the cabin. It's like not enought heat to keep rear windows frost-free. Also my shoes were frozen all the time, not enought heat. Outside temp was -12°C (10.4°F), heat was at max and blower was at max also and directet to windows/windows and floor or floor (depending that where needed). Engine temperature gauge was at the middle and stayed when driving stadily on flat road. With steepest hills i had to shift to 4th (M.W. and fully loaded) temp stayed steadily in the top dead center of gauge BUT, after the uphill (flat road again) when shifted back to 6th temp dropped a little bit and gainet slowly back up (fluctuates a little after hard acceleration and/or steep uphill).

And with urban driving engine wont reach normal if heater is at max and blower is over 2. Upper waterhose that comes from thermostat and goes to radiator is cold after driving so i would imagine thermostat is still ok (but have to check offcourse).

It's like engine is too efficient and wont produce enought heat to maintain temperature. Like with some diesel-engines. Engine is just fine if i wont ask that heat inside the cabin.

One thing came to mind - underguard of the engine bay is missing. Could that cool the engine enought that it becomes diffiult to keep temperature up? This is somewhat strange in my opinion, because my ex-fiat (Bravo 1.2 16V) did not have that underguard and it was HOT. First it was a bit freezing but after swapping the heater core it was truly a warm car. -25°C was the limit where engine started suffering with heat if driven on highway.


Sorry if my english ain't perfect, not a native speaker or writer.


EDIT. Just tested thermostat with MES. It works as it should, but temperature-gauge shows "top dead center" when temperature is 75-98*C.

I think that -25*C and lack of underguard is the main reasons for this. Cabin filter is new and everything seems to work perfectly.

Hmm , can be a servo of the heatermatrix that is not working and simply not letting warm air but just the cold air only. Could also be the interior filter? When did you replace that one?


Anyways you probably need to remove the dashboard. The Stilo was build around the heatermatrix.....

Cabin filter is only 2 months (probably 1500 miles) old. We've had powder snow here in finland now for last 3-4 weeks. Been thinking that could snow somehow get to the cabin filter? If filter is full of snow, it would restrict airflow.

Heater air aint cold, it's warm but not hot. When i tested thermostat with MES i noticed that thermostat started to open at 85°C (185°F) and then engine temperature dropped to about 75°C (167°F). After that thermostat closed again and temperature gained back to 85°C and again temperature dropped etc...

After a while (maybe 10-15min) of revving the engine at 2000-3000rpm (stand still) temperature reached 90-95°C (194-203°F) and air that was coming in the cabin was burning hot (fan speed at max). Engine cooling fan starts at 98°C/208°F.

If stayed at idle and fan speed over 2, engine was cooling slowly to about 75°C (167°C). Outside temperature when testing was only -3°C/26.5°F, so it wasn't that cold that day (no problems when driving on the road).

Thermostat is one year and about 30000km/19000miles old wahler, opening temperature 87°C/188°F. Could this still be malfunctioning? Like if thermostat ain't sensitive and opens/closes too slowly or too much. Needle fluctuates a little, usually after revving engine (overtaking or accelerating hard) it drops a little. And with MES i noticed that needle is bang on middle at engine temp 75-100°C (167-212°F).


Weather here has been cold, -20...-25°C (-4°F....-13°F) and of course it affects heating. Like i said my ex-fiat Fiat Bravo 1.2 was still warm/hot at these temperatures (i burnt my foot because hot center-console) and Bravo has a same engine (only 200cc smaller). With Bravo winter wasn't a problem, all windows were clear and could drive it around without winter jacket. With stilo my feet are frozen and all side windows are frozen, even when fan is at full speed and driving 4th or 5th gear on highway (with 6th there is possibility that engine starts to cool down).

Me and my buddy have tried to find 92°C/197°F thermostat without a succes. I know that there has been a "hot" thermostat for Fiat's FIRE engine, but not available anymore anywhere. That 5°C difference is markable when climate temperature drops below -15°C (seen this with many different engines and cars).

wellu said:

Ok so heater matrix is same kind of pain in the ass as with Fiat Punto mk2. I have to consider that job a little bit before ordering heater core.

Thermostat was walbro genuine so it should be ok.
But today i will check engine temperature with multiecuscan. Temp gauge rises to top dead center (middle of the rating) and stays there if i dont want to have warm inside the cabin.

Yesterday i drove 120km on highway. I blocked radiator with cardboard "just in case" if that helps. Did not help, still pretty cold inside the cabin.

Sorry if my english ain't perfect, not a native speaker or writer.


EDIT. Just tested thermostat with MES. It works as it should, but temperature-gauge shows "top dead center" when temperature is 75-98*C.

I think that -25*C and lack of underguard is the main reasons for this. Cabin filter is new and everything seems to work perfectly.

Click to expand...

Hi

Thanks for the excellent explanation

Ok.. the gauge not moving during @10'c of temp. Fluctuation is ok

DO CHECK the heater hoses get hot when the thermostat opens

IF they get hot quickly.. you have flow..
So matrix isnt blocked

If you still have cold feet.. look for an 'option ' thermostat that remains closed for longer ( keeps engine hotter )


The undertray could help.. because the metallic lower engine would stay dry.. now it is exposed to snow: ice

As well as cooled air

varesecrazy said:

Ok.. the gauge not moving during @10'c of temp. Fluctuation is ok

Click to expand...

Is that 10°C that how it should be? I have 25°C gap where needle ain't moving anywhere (from 75 to 100).

Heater hoses are hot, both of them. Hose that comes from cylinderhead is burning hot and hose that comes from heater and goes to waterpump is warm. So there should be good flow of coolant trought heater matrix.

I'll try to find hotter thermostat.

Yes your 25'c variation apparently is 'ok'

People say thats is what MES shows on their cars..

We had a long thread @2018 discussing thermostats

If the temperature reaches halfway ("90C" on the gauge) and stays there, all while the car is moving, then the thermostat is okay. If it only gets to 90C with the car stationary, but drops to c.75C when the car is moving then the thermostat is knackered.

If the hose bringing coolant into the heater is boiling hot.. but the pipe taking the coolant out is just warm, then that doesn't mean there's enough flow through the heater. The outlet pipe should also be "hot" because the heater fan isn't a Chnihook.. it's a little 12v thing like you find inside a computer.. so it won't suck so much heat out of the coolant. You need to verify that the matrix is flowing coolant - e.g. by disconnecting the outlet (from the water pump end, rather than from the matrix.. saves flooding your car) and then seeing how much coolant comes out when the engine is running.

If there's gallons of coolant coming out.. then check that the heater flaps open fully. You can remove the footwell "gearbox" covers and get your head under teh dashboard (driver's side, if you're Left Hand Drive) and see whether the flaps open and close fully. You may need a small mirror.

If all is well, then it could be that it's just coooooold.... in which case a more robust thermostat could be an option.

Some Stilo's had a spare engine under the car, which provided an auxillary heat source.. but I've never seen it in real life. On the other hand, it could be an idea to add additional heating yourself... something like:

https://www.ebay.co.uk/itm/Universa...307868?hash=item2d1eaee99c:g:MjEAAOSwio1gBqFU

I've never tried it.. so it may be ****e.. but if it was me, and I was minus centigrade every morning, it might be worth a try..


Ralf S.

Do try and bleed air from the matrix hoses again

varesecrazy said:

Do try and bleed air from the matrix hoses again

Click to expand...

Why? Stilo's heating system is self-bleeding.
Actually that self-bleeding can affect to cabin heating negatively. Bleed hose is between coolant reservoir and inlet of heater matrix - part of the hot coolant can go throught this route and "overpass" heater --> less heat.

Then i must say that in Stilo that bleed hose is pretty small and wont flow that much it would affect to cabin heating. In some Opels (Vauxhall) that same bleed is so large that it overpasses the heater and there aint enought flow throught heater matrix to get heat inside the cabin.

Nothing has happened to this problem yet. There has not been extreme cold weather anymore, just about -10°C. At these temperatures cabin is hot/warm enought to feel comfortable. I think that heater matrix could be somewhat blocked (flow of coolant) and i should just flush it with garden hose and radiator cleaner. Anyway, that's not doable right now, must wait for summer (have no warm place to work with car, every fix must do outside and there is just too cold right now).

I managed to find owner of a Fiat Stilo 1.4 Multiwagon here in finland and asked him, how is his car warming at the winter and is engine temp. gauge steady. He said that in the city (temperature below -15°C) engine's temperature is dropping a little - just like i have. And on the road temp. gauge is top dead in the middle of range. But he said that undertray affects drastically to engine temperature.

So i might just flush that heater matrix and buy new set of covers below the engine, if i'm keeping this car over summer and next winter. If so, i'll try remember to raport it here how those fixes helped.

varesecrazy said:

Do try and bleed air from the matrix hoses again

Click to expand...

Actually, this might be the problem/solution. My dad has a MY 2003 1.2 hatcback and i changed it's engine oil in the last weekend.
Weather was +9°C (~40°f) and i let the car idle for 30 minutes to warm the engine oil. After 30 mins i moved the car to the garage and i was amazed how hot there was inside the cabin. Blower was in 3rd and heat at max and i could kinda "smell the hot air" that was coming in.
My 2004 MW does not blow even nearly as warm/hot air to the cabin, not even when i rev the engine.

Only differences between the two raleted to heating:
- Dad's stilo is 1.2 16V, mine is 1.4 16V
- Dad's stilo's oil sump is steel, mine is aluminium (aluminium is better for oil cooling)
- Dad's stilo has minor difference related to cooling system. In 1.2 there is a air-bleed line from radiator to cooling reservoir and there is a bleed-screw in the hose that returns from the heater. In my 1.4 the bleed line is from inlet hose of heater to the reservoir and the radiator has a bleed-screw.

Now, cooling water does not by-pass the heater via bleed-line (flow in that line is so minor, that it wont effect the heating capacity). Althought the bleed-line is at the inlet hose - not in the return hose from the heater. Returning hose from heater comes over the gearbox and drops down to waterpump's inlet pipe - approx 15cm/6 inch lower that the heater outlet. If there is any air it wont escape from the pipes/hoses/matrix of the heater in anyway (air wont reverse back to the cylinder head and go to the bleeding line).

Have to find a outlet/return hose of 1.2 and change that to my 1.4. Let's see if that helps.

Also with thermostats there is some variation. One finn tested few thermostats from different manufacturers, all of them were 88°C. Coldest opened at +75°C and hottest at over 90°C. Few finn fiat enthusiast has tuned the thermostat by changing the element from other car model and manufacturers thermostat and that has fixed some cold unos, puntos etc...

Sorry my english. Early morning at the work and stilo is cold at these temperatures (+5°C). I'm angry and tired as f*ck...

When I was a lad, my old dad used to get some old bonnet liner material and wrap it round the oil filter in winter, like a hot water tank lagging blanket. He held it on with an old CV boot strap (cable ties were more difficult to get hold of, back then).

He also had an old rubber footwell mat, cut to shape and tied to the radiator grille with bent wire.. but thermostats were a) not very efficient and b) new ones, for "foreign" (i.e. European) cars were more difficult to find back then. He probably got a few more degrees of temperature into the engine..



Ralf S.

Ralf S. said:

When I was a lad, my old dad used to get some old bonnet liner material and wrap it round the oil filter in winter, like a hot water tank lagging blanket. He held it on with an old CV boot strap (cable ties were more difficult to get hold of, back then).

He also had an old rubber footwell mat, cut to shape and tied to the radiator grille with bent wire.. but thermostats were a) not very efficient and b) new ones, for "foreign" (i.e. European) cars were more difficult to find back then. He probably got a few more degrees of temperature into the engine..



Ralf S.

Click to expand...

Yep, i've seen some VAG diesels with the oil sump blanket/heat insulator. Something soft material (like heat/noice insulator) wrapped around the oil sump. Haven't found anything like that anywhere.

I've got an under-tray on mine, which probably keeps a fair bit of the draught out/heat in... but when it's *cold* here, it's still just -5C or something.. so my heater doesn't really struggle. I think I've only had it on "MAX" two or three times ever.

If the thermostat is on "88" (halfway) then the heater should be toastie, like your dad's car.

Ralf S.

Hi again!

Thanks for comment Ralf. I bougth the under-tray (all 3 of them) and replaced the broken pieces last weekend. I also changed thermostat - just in case. There is now new 87°C thermostat and i lso flushed the heater matrix and engine with hot water. After all that i made a "diy" bleeding line to the return line from the heater. I managed to bleed the system perfectly (no air in anywhere) and had a really high hopes...

...so, it's now about -10°C here in finland and engine keeps heat pretty nice (needle top dead center), but inside the cabin is still "too" cold. I can feel the air coming in from heater vents is somewhat warm (i'd say something like +20....30°C) but not hot. For excamble, my father's stilo is blowing painfully hot air from vents when driving.

Today i blocked the bleed-line from heater inlet. I figured that maybe water is by-passing the heater by some amount throught that bleed-line. This helped a little bit and car was nice to drive in -8°C weather.

From experience i know that this is not enought - when outside temperature drops somewhere -20°C or below, heat wont be enought to keep glasses etc. dry or even ice-free. Again with my father's stilo, -28°C isn't an issue (you can drive it in those temperatures without a winter jacket - just hoodie and normal shoes + trousers).

Next step is to try some engine coolant&radiator cleaner, drive with it few days and flush the heater again. Both heater hoses are hot/warm but i think that there must be something blocking the heater matrix partially or something.

How hot is the air coming out of the dashboard? Stick a thermometer on there and see what comes out.

Also measure the temperature of the hoses going to/from the heater, if you have one of those laser thermometers. You don't need the precise accurate temperature.. it's just a reading that you can compare them to your dad's car. Whatever readings you get, they should be very similar, even if the engines are different.

It'd be interesting to prove whether the coolant is hot but the air is only "warm".. or if the air is only warm because the coolant is warm.

Meanwhile... auxillary electric heater as fitted to the diesel, if you can find one.. I think these push some warm air into the fuel tank, rather than the cabin.. to keep the diesel fuel from waxing up... but you can route the outlet into your footwells..

Ralf S.

I measured some temps with IR meter.

Engine temp normal (needle top dead center), thermostat started to open and upper waterhose was warming. Blower at 3 and max heat.

Air from vents: 32°C (89.6°F)
Heater inlet hose: 35°C (95°F)
Heater return hose: 27°C (80.6°F)

And some high revs. 3 minutes at 5000rpm and same measurements:
Air from vents: 60°C/140°F (acceptable)
Heater inlet hose: 65°C/149°F
Heater return hose: 48°C/118.4°F
Upper water hose: 65°C/149°F

Thermostat is brand new 87°C Calorstat and works fine (boilied water in the kettle and tested the thermostat before installing it, started to open at 85°C)

The IR meter that i use is a bit funky with materials, so i assume that water inside hoses is something like 15° more than measured. Air temp is correct. Can't compare to my fathers car right now because he lives 230km apart from my place.

15 minutes of idle when cold starting at -15°C wont warm the engine or dash vents at all (feels like it).

If you remove pollen filter what it happen ?

At 35 degrees you can keep your hand on the hose. Too low a temperature there, not good.