Technical Overheating nightmare puzzle!!!

[288gto]

Hi, I have officially lost hope (once again) of resolving this simple and yet highly complex issue on my 1.1 Sporting.

I noticed the car was running a bit hot getting over 90C and even with the fan coming on the water was coming out of the cap. So as the bits are cheap I bought a new genuine thermostat, fan switch, radiator and winter coolant. Replaced everything, bled it and still no change but now the fan stopped coming on as well when it goes over 90C.

I tested the fan by running the wires direct to the battery and it worked, tested the wire coming to the fan (it does have power) also took the plug of the fan switch and shorted it to discover it works then as well, the fan fuse is fine too but still it doesn’t come on when the gauge reaches 90C.

Any ideas gentlemen?

 

[fingers99]

I would (not necessarily in this order, BWTH):

Do a compression test
Swap out the thermostat for a bona fide one (Halfords, FIAT, eurocarcare.net or Shop4Parts)
Check the condition of the radiator -- new ones are absurdly cheap
If the rad is OK, use radiator flush (follow the instructions) reverse flush as much of the system with a hosepipe as you can, replenish with the pink stuff (it's the same price as the blue stuff now)
Check the water pump
Check the thermoswitch with a thermometer, pan of water and an ohmeter.

 

[288gto]

Yeap, new rad in, new thermostat in, new coolant, new fan switch, water pump was done along with the cambelt last year and doesn't make any strange noises.

I have even dipped the fan switch (while connected) in a kettle and boiled it to see if that would trigger the fan but no joy (with new and old one). What other aspect is involved to make the fan go I wonder?

 

[fingers99]

See if you can bridge the terminals of the fan switch (with the socket/plug connected) with a paper clip. If the clip gets very hot, it points to a failing fan motor.

But I'd do a compression test, ASAP.

 

[Pep0]

from cold the hoses should get hot in sequence

mini hose from throttle body to header
heater matrix hoses
thermostat hose
bottom rad hose

you need to have bleeded the matrix and rad

if the bottom hose is not scalding hot but the hoses are hard then you have no circulation...

blocked pipe
blocked rad
airlock
pump kaput
thermostat kaput

if the pump is ok the heater will be really hot even if the thermostat is closed
if the pump is kaput only the header to throttle body will be scalding

the pumps can fail e.g. the OEM plastic impellors can turn into granules all by themselves my last did 12k miles.

thermostats even OEM ones ditto

so drain replace thermostat inspect pump e.g. is impellor still on shaft

even more fun replacing head gasket if you let it overheat one time too many

 

[288gto]

Actually I just had a look on ePer and spotted a component I haven't changed yet It's a temperature sender unit;

http://www.ebay.co.uk/itm/Sender-Un...SM&fits=Model:Cinquecento&hash=item1c3572ed9d

Would that have anything to do with the fan not working?

 

[fingers99]

On a Cinq or SPI Sei, no.

Compression test.

 

[288gto]

I have booked it for a compression test on Monday so won't be using it until then. However I spoke to Fiat and they told me that this sender unit notifies the ECU of the temperature and then ECU greenlights the fan to operate. Is that right? Thant's on a Cinq 1.1 Sporting SPI

 

[fingers99]

No. They're thinking Sei MPI.

The Cinq circuit is old school simple:

 

[288gto]

That sounds about right because I was looking under the bonnet yesterday and couldn't see a thing apart from the gauge temperature sensor on the back of the block by the battery.

 

[Pep0]

borrow a compression tester from neighbour...

 

[frodovic]

Please measure the size of your radiator.

A friend of mine solved a similar problem this week and we found out the new radiator he bought was a lot bigger than the one he had fitted.

He also had a blocked radiator and we went for a full replacement of all water tubes (even the spider shaped one) while we were at it, also change expansion vase and cap for new ones (his expansion vase was from another car, not a Cento Sporting)... We also changed the valve that triggers the fan that is bolted to the radiator.

His car had the same behavior as yours. The fan wouldnt come to play at 90 degrees and the temp kept climbing to more than 100. When it switched on it couldnt bring the temp down. The car is now fine. Mine is waiting for the parts to do the same in the next few days ...

Do you lose coolant ? Have you checked the level ?

 

[blu73]

compression tester is like £15, you own a cento - you need a compression tester, go buy one

and for your info, that sensor you linked in located on inlet manifold, and nothing to do with radiator, its so ecu knows how hot engine is and adjusts fuelling to suit. One on back of head is for the dash temperature warning light on sei & basic spec cinq or temp gauge in cinq sporting.

Regarding your cooling issues, does it get hotter than 90degrees or does the fan cut in and it cool down a bit. I ask cause 90 degrees is normal if its going slow/idling in traffic etc, should drop when moving along - how much it drops depends on many things but say 75ish degrees on a flat road at 60mph. If you leave it idling does the fan cut in and out or just once it comes on its on and the car doesn't cool down enough for the fan to stop again???

 

[Pep0]

you said water was coming out the cap?

the engine needs anti freeze all the year around the cylinder head is aluminium and will dissolve in hot water.

the cap is a one bar pressure relief if it has geysered too often it may blow off at lower pressure

the anti freeze and one bar pressure allow 120 C before geyser unless you have a leak or a compromised head gasket - hense fingers request for compression test

I leave my cap in plastic bowl over night with plastic kettle descaler or buy a new one after a geyser

if gauge goes up turn on heater and heater blower to max...

 

[blu73]

good point there, i meant to say replace cap as well, they do fail from time to time.

 

[288gto]

Normal temp when I’m driving along at 60mph is dead on 80. In traffic it tends to get up to 90 and would stay there, however now the fan does not kick in at all and if left rocks up to 100 no problem. When it reaches 90 however the cap starts releasing fluid, I think I have a blue Sei cap, would that be the same?

I have felt the lover rad pipe and its quite hot so struggling to understand why that stupid fan won’t work (new rad and new fan switch installed).

Also noticed some air bubbling through a bit of fluid around the spark plug closest to the reserve tank but not sure if its there because it spilled out of the tank or coming out of the engine.

I’ve been away for a week and used the car today. It’s fine when you keep moving but then the temp rises again in traffic, so I counteract it by putting the heating on full blast and it comes back down below 90.

PS. I only ever use the red coolant, never water on its own.

 

[blu73]

well you need to find out why the fan isn't going, the cap releasing pressure means that it is working, thats whats meant to happen if the coolant gets too hot to prevent over pressurizing the system (which generally results in the weakest part exploding, which would be the plastic expansion tank).

Does the fan turn freely by hand & if you bridge the 2 wires on the fan switch does it start the fan?

 

[fingers99]

Does the fan turn freely by hand & if you bridge the 2 wires on the fan switch does it start the fan?

You were asked to do that a week ago!

If it comes on, rad switch is suspect. If it doesn't earth is suspect. Do check the fuse, though!

 

[288gto]

The fan is free and has been tested by myself twice by connecting it directly to the battery and it works fine. The fan fuse looks good but replaced it for a new one. Fan switch is new, tested it by putting the old one in and leaving the new one in a boiling kettle while connected to the system to see if it will make the fan go but no joy. Also tested the wiring going to the fan switch with a meter and it shows power.

 

[fingers99]

With meter on continuity, discover which terminal in the fan switch connects to the battery. Then, using a piece of cable, stripped both ends, jump the other terminal to earth.

Post results.