hmmm what the f**k?

[payney8]

Hey guys bit of a problem with the m20 today.
I replaced the temp sender/switch the single probe one. And all was well topped up the coolant a bit and went for a drive temp was good gauge was reading. Then i let it sit for a couple of hours. Took it for another drive still good. Then gave it a bit onto the highway and noticed the gauge was pegged so pulled over straight away and had a look. No leaks still full of coolant and the temp wasn't that high. Like i put my finger in the coolant and it was hot but not boiling. I noticed there wasn't much pressure in it though. So i gingerly drove it home and disconnected the sensor it dropped to nothing. And check my temp send got a reading of 270ohms.Then i let it cool for an hour till the gauge read under blue. Started it up fans working, checked all my hoses and they aren't very pressurised but i noticed the one going to my thermostat was pressured after i let it cool down so its getting pressure and i checked my fan play and its ok. Could it possibly be a faulty sendor? or any ideas its my dd so i need assistance asap :)

[payney8]

oh and before i replaced the sender it was all good never got hot

[payney8]

Just took it for another drive and it is fine until just b4 the quarter temp mark then it just shoots up to peg. Makes me think that its the sender?? the bottom hose on the radiator is cool the top one is hot and the feed is hot. so its cycling. Any ideas?

[payney8]

anyone????

[maniacmatt]

Did you bleed the cooling system after you installed the sensor? Maybe you have air in the system.

[QUKBMER]

Correct ! Need to turn on the heater and if you can elivate the frontend of the car upwards with jacks or jack stands alittle and bleed the cooling system. Are you running electric cooling fans or stock fan clutch type?

[payney8]

Stock clutch type fan. So just lift the front up and pull the bleed plug?

[payney8]

Undid the bleeder and no air. Also there was pressure in the system one i released the cap. And again it stays fine till it hits the quater temp mark then it shoots to pegged

[payney8]

Tried it a few more times and they gauge gets to 1/4 temp then shoots up to pegged. Drove it for an hour and checked temps on the hoses. All good. No steam or milky way oil. Looks to be a sensor fault. Any one agree

[slo325i]

When the car is properly warmed up, your rad hoses should be very well pressurized and HOT to touch. Is it?

[payney8]

yeah they are pretty pressurised i wouldnt say 20psi pressure but there is some there. No more or less then before i fitted the sender. And they are hot to touch and the bottom radiator hose is cooler then the top but still warm

[payney8]

It was the switch got a genuine bmw item and fault disapeared