General Good news problem sorted I think

[Fiat Ducato Motorhome]

So for all thos who followed my thread regarding the overheating/running hot once at speed especially on the motorway. Well I think I've finally sorted it. I recently changed the water pump (although the olf one wasn't plastic and wasn't slipping) changed cam belt and tensioners at same time, problem was still there, noticed bottom hose was stone cold even after a long run on the dual carriageway when temp was above halfway. So ordered new thermostat, emptied coolant, added some decent rad flush and gave it a good run, emptied all out, back flushed the complete system especially the radiator. Fitted new thermostat, replaced the bottom rad hose and top rad hose, added new coolant and took for a test drive.

Noticed it takes quite some time to reach normal operating temperature even when driving around 10 minutes maybe more. Doesn't go above halfway now on the gauge (90) but what I have noticed is that when criusing at speed it stays at 90 but as soon as I slow down junctions, round a bouts, town etc, the temperature drops slightly below 90

Is this normal?? or could it be some trapped air stil lin the system?

Also noticed that unlike before when I unscrew the expansion tank cap there used to be air, now there is none at all which is a good sign. Speaking to a mechanic who explained to me that if the water isn't circulating properly either through faulty water pump, radiator or thermostat. Pressure can build up, like a kettle as an example.

 

[oigle]

So for all thos who followed my thread regarding the overheating/running hot once at speed especially on the motorway. Well I think I've finally sorted it. I recently changed the water pump (although the olf one wasn't plastic and wasn't slipping) changed cam belt and tensioners at same time, problem was still there, noticed bottom hose was stone cold even after a long run on the dual carriageway when temp was above halfway. So ordered new thermostat, emptied coolant, added some decent rad flush and gave it a good run, emptied all out, back flushed the complete system especially the radiator. Fitted new thermostat, replaced the bottom rad hose and top rad hose, added new coolant and took for a test drive.

Noticed it takes quite some time to reach normal operating temperature even when driving around 10 minutes maybe more. Doesn't go above halfway now on the gauge (90) but what I have noticed is that when criusing at speed it stays at 90 but as soon as I slow down junctions, round a bouts, town etc, the temperature drops slightly below 90

Is this normal?? or could it be some trapped air stil lin the system?

Also noticed that unlike before when I unscrew the expansion tank cap there used to be air, now there is none at all which is a good sign. Speaking to a mechanic who explained to me that if the water isn't circulating properly either through faulty water pump, radiator or thermostat. Pressure can build up, like a kettle as an example.

Your expansion tank should carry pressure when the system is hot. f you don't have pressure, the cap is crook or you have an air leak somewhere else. The pressure is necessary to raise the boiling point of the coolant.
The thermo should hold your temp at a solid 90° under all conditions and no vary. If you are getting ups and downs, you still have an issue.

 

[varesecrazy]

Somebody pointed out to me that the gauge SHOWING 90'c...can inicatd REAL coolant temps between 60 and 90.

That is why you sometimes see the needle leap up from cold.

The gauge dipping when no longer pushing the motor is not ideal ( pointing to a poor regulation in the waterpump..)


But my best ever diesel did this its entire 300,000 miles with me.

In reality this would lead to inefficient engine temp..more fuel used.


If it is 100% leak tight..

Level holding perfectly..

I would give it 500 miles..and see if things change.

But your call really.

Charlie

 

[Fiat Ducato Motorhome]

Thank you guys for your comments, really not sure what it could be. No leaks at all, no drop in coolant. Coolant expansion tank is pressurised when system is hot just not when cold like it was previously. Had sniff test to check head gasket. Had new water pump and cam belt about a month ago, also had new radiator, new heater matrix, new temp sensor new thermostat and new hoses this time. Been flushed and back flushed several times. Removed expansion tank and cleaned it, had new expansion tank cap also. Have no idea why its behaving so oddly. Was hoping it was just still a bit of air in the system as only took it out twice since changing thermostat.

 

[oigle]

As Charlie sort of suggested, could be a faulty gauge.