Conflicting waterpump info

Paulo

Having just driven home with the temp gauge and heater going to zero when on the motorway and then climbing back to normal (12 o'clock) when idling or going slowly I nipped into the local garage where he told me I probably need a new waterpump. With my limited knowledge wouldn't I be looking at a new thermostat instead? Having Googled it seems a failing waterpump will cause the temp to rise above normal which is what I already thought. A falling temperature is surely down an open stat surely? The guy wants to strip out the pump to see and it looks like a hefty job and will cost. There is no apparent sign of any malfunction other than the temp drop when going above 30 mph. Any thoughts are welcome.

Phil_aka_Pip

I agree - try the thermostat first. I hope you don't have a Poxhall engine which requires the cambelt to be taken off before you can access  the thermostat.

Paulo

Yeah Cheers. I'll prob go somewhere else actually. It's a mondeo 2.0 petrol.

Phil_aka_Pip

Paulo said:

Yeah Cheers. I'll prob go somewhere else actually. It's a mondeo 2.0 petrol.

One would hope that a Ford engine would be relatively easy to check over without specialist help. Even changing the pump shouldn't be too much trouble.

Axe_meister

The stat went old my old Mini Cooper (modern one) you had to remove the entire water inlet manifold and a whole lot of other stuff to get at it. It was showing overheating just when I switch the engine on

boogieman

Yeah, I'd say it was a thermostat problem, although it doesn't fit the classic symptoms tbh (Engine running cool all the time). A waterpump failing usually shows up as knackered bearings/seals and then the engine starts to lose coolant. If there's no signs of any coolant leaking round the pump, I'd investigate the thermostat first.

Paulo

I'm thinking if the stat is stuck in the open position there will be a feed from the radiator all the time so going on the m/way will overcool the engine, espy in this weather. It warms up when idling as there is neglible cooling coming from the radiator. So to me it seems to fit with the stat issue. That's why I was surprised when the mechanic targeted the waterpump before he even looked at it.

Fuzzdog

With those symptoms, I'd have gone and bought a new thermostat without really even poking at it more - sounds like a classic stuck stat to me.  I'd certainly not be suspecting the water pump from those symptoms.

speshul91

Stat. Put it in a pan of water and bring it to the boil see if it opens at all is best way to check em

Paul_C

speshul91 said:

Stat. Put it in a pan of water and bring it to the boil see if it opens at all is best way to check em

Isn't that cooking mussels ?

suspiciousminds

I reckon thermostat, had a similar problem with an old ford capri.
fluctuating temp guage then stuck open and temp dropped, poor heating too.

chillidoggy

Check the coolant level first.

Emp_Fab

Paulo said:

I nipped into the local garage where he told me a crock of shit to try to rip me off.

Corrected for accuracy.

As others have said - highly unlikely - nay impossible - to be the water pump.  Stuck thermostat.  

Paulo

Thanks for the replies. I was almost going to cancel a days work tomorrow as it's a good distance away but I'll risk it now. I'll take the car in on Monday, I'm useless at car stuff myself. Cheers.

monquixote

My wifes car does the temp gauge thing. 

Common fault in things with the 1.9TDi engine that's in loads of VAG cars.

In that case it's a coolant shorting out the thermostat sensor. 

No idea if it's the same problem in the Mondeo, but I don't see how it could be the water pump.

mike_l

I'd try a new temp sensor first.

Pretty common to go wrong.

FX_Munkee

Agree that the symptoms are open thermostat.
A quick test to check the sensor would be turning on the heating when the gauge is showing "cold" ie when travelling at decent speed with no real load on the engine.
If it blows hot (properly hot not just a bit) it's quite possibly the sensor, otherwise thermostat is duff as suspected.

Paulo

It blows cold for ages and only warms up a bit when idling. Def thermostat. Cheers.

Paulo

It was the water pump after all! A couple of the impeller blades were broke and it wasn't powerful enough to push the hot water from the engine round to the rad. No hot water in the rad, so no heat. :-)

FX_Munkee

Paulo said:

It was the water pump after all! A couple of the impeller blades were broke and it wasn't powerful enough to push the hot water from the engine round to the rad. No hot water in the rad, so no heat. :-)

Curious. I'm left wondering where the hell you're engine water temp sensor is. As the symptoms you described would fit (for water pump) except for the temp gauge showing cold, it should have shown hot.

Paulo

The temp sensor on one of the water pipes from/to the engine I believe going to the radiator. The sensor was changed first but had no effect. It was explained that the hot water was staying in the engine and not getting pushed around the cooling system as the water pump was working at a fraction of its requirements. It's working a treat now.