Mk 4 Mondeo ....overheats after 30 minutes drive!

ethical

Hope one of you can suggest the issue here! Thanks in advance.My friend has a mark four 1.8 diesel mondeo,a very economical car but recently there has been an ongoing issue.She noticed coolant fluid level dropping and topped it up a few times over a couple of weeks but then went on a longer than usual journey where after 30 minutes driving the needle on the tenperature gauge just went way up ,she stopped right away but was able to drive again after 10 minutes.A garage checked the thermostat valve and there dosent seem to be an issue there but there is a build up of pressure culminating in the coolant tank leaking .Seems the coolant is not circulating? Any ideas what the issue is.Its fine for the short journey ,school drop offs etc but this problem seems to rear its ugly head when there is heat and pressure built up after about 30 minutes driving.Thanks!

K.Flyer

Diesel engines take a lot longer than petrol engines to heat up fully. I would think there is an issue with the water pump or a blockage somewhere. Did the garage check the water pump?

dev100

It's an expansion tank so coolant will measure differently when hot and cold so tell your friend not to overfill it either
It will be pressurised to a certain amount.

When you say it's leaking can you physically see where it's leaking out of expansion tank ? If you can see where it's leaking and it's being topped up it could be a head gasket if no leak is found

When she turns on the heaters is running hot or cold ?

Not sure about the pump. On vw s it's connected to the timing belt system it could be cause if coolant cant circulate properly. What's the mileage on the car think they are a timing chain job

sunnysoutheast

Sounds like the water pump may have seized.

ethical

Thanks for your replies.She told me the water pump was checked and that its ok.The belts were done also a couple of months ago.The thermostat was also checked.It sounds as if it may be a gasket. The mileage is around 100,000 miles.Are the gaskets expensive to sort out?

martinr5232

Water pumps were a bit troublesome on those i seen a few where the impellor came off inside the pump and wouldnt circulate the coolant.
Thermostat housings also leaked and water pumps leaked hopefully its one of those because a headgasket would be very expensive.

Dilbert75

martinr5232 wrote: »

Water pumps were a bit troublesome on those i seen a few where the impellor came off inside the pump and wouldnt circulate the coolant.
Thermostat housings also leaked and water pumps leaked hopefully its one of those because a headgasket would be very expensive.

This would be my guess too but the pump will look fine from outside. Where a pump has a plastic impeller they can crack and the shaft spins without the impeller. So coolant will circulate by convection when moving but when the car stops it overheats quickly. Aftermarket pumps with metal impellers are far superior.