XU5M3Z Coolant woes

[Depleted 1 1 Cars]

Hi everyone,

 

I've had my 205 for 4 years come this april and just this year i've had some rather concerning issues with the cooling system. Within 15 minutes of the engine running and being at idle the stop light and coolant temp lights come on, now this wasn't such a concern before around summer as i could hear my fan kicking in to high-speed mode but around autumn when areas of my home town were absolutely saturated and flooded with water I hit a few giant surprise puddles that drowned my engine bay in scummy water and I had to pull over on one occasion as the amount of steam that was chucking out of the engine bay was insane.

 

The fan has refused to work at all during operation even when the two warning lights are glowing a bright red. If i start driving the radiator gets air rushed through it and within a few minutes of being on the move the warning lights dim down and eventually fade away until i come to a stop again. God forbid i get stuck in traffic or go to mcdonalds drive thru, i have to kill the engine out of fear i may cause irrepairable damage to something as within 10 minutes of idling the warning lights are nearly as bright as the handbrake light.

 

I've unplugged the connector for the radiator switch and bridged the three positions to confirm the fan receives power and works in both low/high and in the off position, i've removed and tested the switch by heating it while plugged in and it functioned, I've even replaced the switch with two different units that bring the fan on at a lower temperature, by default my automatics switch is the 97.5c one - again i tested these switches by heating them up by sitting them in water and heating the water with a butane torch from below and they worked, I've replaced the relay, i've completely removed the radiator assembly and flushed it out from both ends as i accidentally broke the drain valve, well the stem snapped off from the radiator body when i tried to loosen the threaded fitting and upon closer inspection i saw the amount of solder on the joint was pisspoor so i cleaned it up as best as i could then fluxed and re-soldered the fitting and flushed the radiator again, the threads are completely seized and i couldnt find a replacement part so im stuck with a non functioning drain valve, yay.

 

When testing the system i can make the fan work, but when driving/idling and trying to raise the temperature of the coolant to induce the fan I get nothing, no low speed or high speed even when my radiator is boiling hot and the coolant pipes are hot, i've bled the system, the heater matrix produces heat in the cabin, im assuming the thermostat works fine as the coolant runs through the system, the radiator gets hot all over as does the rest of the system, I can't find a cold spot, I've removed all the connections and cleaned them with contact cleaner, I've checked all the fuses and wiggled connections and everything seems ok but still i get no fan assistance.

 

I have just received new coolant sensors 2&3 that go into the back of the block by the distributor, from my limited knowledge the red banded sensor is the warning light and the other sensor right next to it is the sender? I'm praying that when i replace these later today it will fix my problem but i'm doubtful as I can get the engine roaring hot to the point my radiator is steaming from condensation vapourising. 

Correct me if i'm wrong but I was under the assumption that as long as the switch, resistor, relay, wiring, and fan are all good, then the cooling system will work, as the sensors in the block are just to activate the warning light and to tell the ecu the temperature to adjust the fuel mixture for cold starts etc?

Any ideas or insight would be most appreciated as knowledge about this model is pretty non existant and i've been banging my head against a brick wall for the better part of 5 weeks now trying to sort this out.

Edited February 13, 2021 by Depleted

[PhilNW 43]

I would expect some vaporising as the system warms up, the switch kicks in at 97? but the system can run hotter than that due to it being pressurized.

 

Can you get hold of an infra red thermometer to check actual temperatures of the radiator etc

 

Has it actually boiled the water while ticking over/warming up?

Edited February 13, 2021 by PhilNW

[Depleted 1 1 Cars]

I don't know anyone with a infrared thermometer sadly, my only option would be to take it to a mechanic who might have one if that's the case unless they can be picked up on the cheap.

I understand the cooling system is pressurised to raise the boiling point of the coolant, and I have noticed the expansion tank level dropped from near to the max line to below the min line from the last 2 weeks of use going to and from work etc.

As it's rather cold out right now - could i in theory be wasting my own time trying to diagnose this issue when it's difficult to get the coolant near boiling point to see if the system actually functions properly?

 

I've just replaced the two sensors with the new ones, I let the engine warm up for about 10 mintues then i took her for a spin around the ring road and at no point did the warning lights even light up dimly, the coolant level light came on as i expected from losing some coolant when replacing the sensors but I topped her up and bled her again to remedy that.

 

 

While i was down in the bay fitting these new sensors i noticed a wide opening that seems to be connected to the airflow sensor part of the intake system, a few years ago when i opened the hood to check fluids and such I noticed a similarly sized in diameter heat shielded part of tubing (about or over a foot long) that was completely loose and was sitting on top of the engine somehow, please don't tell me that pipe was connecting these two openings, and if so how do i identify that pipe so i can get a replacement? I'm clueless and learning as I go.

 

Ok so after  browsing the legendary miamistu site i found that pipe, it's part of the air reheating system

05

1425 F8

01

HOT AIR PIPE

http://www.miamistu.co.uk/pug/GB/205N/1/14K70A.HTM 

 

Well atleast that's something else i've identified and can replace even though i have no idea what its purpose is.

 

 

Edited February 13, 2021 by Depleted

[PhilNW 43]

Something like this https://www.screwfix.com/p/magnusson-im23-infrared-non-contact-digital-thermometer/1352x used by plumbing engineers to check radiator temp.

 

Even in these recent cold days engine should eventually warmup , maybe wait until later this week when air temps are due to go up.

 

The pipe you mention is to aid engine warm up by taking hot air from the vicinity of the exhaust manifold and mix it with external air into the intake manifold.

 

Would not worry too much about reduced level of coolant at this stage, cant see it being related to the fan not kicking in. 

 

 

[Depleted 1 1 Cars]

Ah ok brilliant thank you very much Phil, I've ordered the infrared thermometer so hopefully i can use that that to monitor the temperature to see if im even getting near to the mark where the fan needs in order to kick-in as this car does not have gauges, it just has bloody useless lights.

 

I've ordered a 75cm length of 2ply thermal silicone heating pipe and extra jubilees so i can sort the reheating system out too. I just taken her out for a spin to go get some essentials and the warning lights lit-up when the ignition is switched on on so im guessing the new sensors are working as the warning lights weren't even dimly lit where as prior to the sensor replacement they would of been somewhat illuminated.

 

I'll report back with an update when the bits arrive and i've been able to test everything.