Header tank overflowing

[lancer]

Hello,

I have a problem with my 2000 406 HDI 90, When the car runs for awhile the temp gauge gets to about 85c and stays there even when the car is idleing in my back yard then after awhile it will start to blow water out of the header tank and the cooling fans never seem to kick in at any time i have replaced the coolant temp sensor and still no luck. I have recently changed the head gasket as oil was overflowing to my header tank so think this problem maybe blew my headgasket. When i disconnect my coolant sensor the fan comes on at full speed and the temp gauge inside the car jumps up to about 100c and also water level drops in my header tank and remains low for however long my fan is running. Is there a second temp sensor anywhere that kicks in when the other is removed or will the temp gauge always jump to 100c when you unplug that sensor?

Any help on this issue would be great cheers.

[teamster1975]

Welcome Lancer!
There are two temp sensors, the one that you unplugged, the other I'm not sure as to it's location.
When you refilled the coolant did you bleed the system? It sounds like an airlock to me. There's a bleed screw on the thermostat and near the RH bulkhead for the heater matrix. If there is an airlock the coolant sensor would never get an accurate reading. Either that or the sensor is faulty.
Are you getting any heat from the blowers?

[steve_earwig]

Good point, I suppose the fan switch might be sitting in an air bubble.

Wiki bleedin' cooling system http://www.pug406.com/wiki/index.php/Bl ... ng_System) (or park the offside on a high curb )

[lancer]

Yeah i have bleed the system i think right and also replaced that sensor. Does anyone know the right temp for the fan to kick in at either low or high speed also when i stick on the AC the fan doesnt kick in. Starting to think it might be the relays on the fan thou it kicks in at full speed when i disconnect the temp switch so not sure if that means the relays are ok or not.

[teamster1975]

At 90 the fans come on at half speed, I think it's 100 they go full speed.
Could be the relays I guess...

[lancer]

The car only seems to blow water out when its sitting still for a period of time running, as when i take it down the motorway at 70-80mph the top of the header tank is clear of any traces of fluid. Does anyone know if it was the head gasket would it blow water out regardless of car moving or not?

[teamster1975]

That's pretty weird. When I've had HG's go before it's only been at higher revs that the coolant gets pressurised & blows out. (My bike at the moment actually! )
You sure the water pump is ok?

[lancer]

Well when ever the car is at temp all the hoses that should be warm are warm so never really thought it would be a water pump issue. Rad is also warm all the way up and down it no cooler spots. Going to try and get a garage to do a pressure test and try and rule out the head gasket.

[Welly]

You're not over-filling the expansion tank are you? My 110HDi did this once when I put too much water in - it just spat it out!

The fill line is the bottom of the filler cup thing inside the neck of the bottle. Any further up the filler neck and it will spew it out.

Also feel the rad hoses when it's doing this to see if they are rock-hard?

Maybe also a new filler cap is worth a try? yours may not be able to keep a pressure and it's letting the water expand too much.

[jasper5]

Welly has a good point, also get the garage to do a chemical "sniffer test", that will clear up the head gasket issue.A pressure test may not always show a faulty head gasket.

[lancer]

The water in header tank is at correct level and even with the cap not on it still overflows going to try and get a garage open today and get test done to see if the head gasket is gone or not. Does anyone know the best product for flushing the cooiling system till i make sure i have got rid of all the oil from the old head gasket failure and i have not still got oil coming in to the cooling system.