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Matt, Mechanical Engineer
Category: Ford
Satisfied Customers: 22758
Experience:  BEng hons Mech engineering, in auto industry 22 years
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i have a ford transit connect was all ok then no heat inside

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i have a ford transit connect was all ok then no heat inside and engine temperature started to go up then fall when driving slower (was town driving). garage first changed thermostat then water pump (propeller had disintegrated) system was flushed and pressure tested all ok drove over 200 miles on motorway but just befor i got home temperature quickly went into the red turned engine off and pulled over found coolant boiled over and expansion tank was empty. when back to garage who could find nothing wrong van was ok driven slow but on motorways after about 10 minuets it would overheat and empty expansion tank. it went back again still found nothing wrong.
i have found no leaks but found radiator fan not coming on when over heating. tested fan with a battery found fan failed replaced fan now working but again on motor way over heats but only at 70+mph but when slow down it quickly cools back to normal (not fully emptying expansion tank.
any ideas could thermostat they replaced have failed?

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Customer: replied 3 years ago.
I want an answer
Customer: replied 3 years ago.

i would like an answer or at lest tell me you can't answer



if the system wasn't bled properly then yes its possible its cooked the new thermostat so I'd suggest fitting another thermostat

Whilst the thermostat is being replaced you might as well also reverse flush the cooling circuit (remove top hose to rad and use a hosepipe to push water into the engine until you get clear water out of the radiator hose) and top up with 30-50% fresh antifreeze. Also check that the small diameter bleed hoses that run from the top of the radiator and the top of the engine aren't blocked as this allow the air to vent back to the header tank automatically.

If you still have a problem then check that the water pump impeller / turbine isn't spinning on its shaft. You should be able to achieve this by removing the bottom hose from the engine and use a screwdriver or similar to feel for the water pump impeller blades, whilst your assistant turns the engine over by hand.
If you can stop the impeller with slight pressure from the screwdriver the pump needs replacing.

Also its possible the belt is slipping so its worth replacing its especially if the rubber ribs are cracked or it looks shiny on flat side of the belt - while its off check that the tensioner and other pulleys all spin freely the exception to this is the AC pump ( if fitted)

I'd also suggest ensuring that you've got all the air out of the system as this sort of episode can leave pockets of air trapped and prevent the coolant from circulating properly.

So check that the small hoses that run from the top of the engine and radiator that run back to the header / expansion tank are free flowing and not blocked

If these are OK then remove the tank pressure cap and run the engine from cold with the heater set to full hot

As the engine starts to warm, squeeze the large hoses running to the radiator to help displace any air - all the time keeping an eye on the level in the header tank, making sure it doesn't drop below the minimum and open any bleed screws built into the top cooling hoses - closing them off as soon as they start to gush water

Once the engine is up to temperature the tank should be quite full. Switch the engine off and leave it to cool

Then top up to the mark once its all cold and replace the cap

If all of this is OK it may be worth replacing the header tank cap as again you can lose coolant as steam if this is blowing off too early ( the cap should hold pressure of around 1Bar)

The other thing to try is a head gasket / block test kit as these take a coolant sample and analyse it for any signs of combustion gas - if present this would indicate the head gasket is on its way out

Customer: replied 3 years ago.

thank you for replying just extra info timing belt was changed at same time as water pump

the header tank cap is also constantly hissing.

Could a new pump have failed?

is there any bleed points on connect? i haven't see any

both small return pipes when revving engine have return flow.


I don't think there's any bleed points just the small hoses that run all the time

and if the header tank cap is hissing all the time then it could be faulty or the engine could be making a lot of gas

in which case if a new cap doesn't help then try the block test kit
Matt, Mechanical Engineer
Category: Ford
Satisfied Customers: 22758
Experience: BEng hons Mech engineering, in auto industry 22 years
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Customer: replied 3 years ago.
Just to let you known it is the bead gasket
Customer: replied 3 years ago.
Head gasket has been replaced now oil light is flashing.
Oil pump, oil sensor and filters have been replaced. Mechanic is now stumped
Hope you can help


I'd 1st suggest measuring the actual oil pressure with seperate mechanical gauge - this can be plumbed into the engine via the current pressure switch port - if you use a Tee piece you can keep the pressure switch plumbed in as well and so see if the low pressure light corresponds to a low pressure reading.

As its intermittant and you have no rumbling or rattling noises from the engine its likely to be an electrical fault so 1st check the connection to the pressure switch is bright and clean and check back along the switch wiring for any signs of damage to the insulation

As if the wire is grounded out at any point then this will also turn on the light.

If you do have a low pressure reading and to turn on the light it will be very low about 5psi then replace the oil pump and ensure that the pump pickup in the sump hasn't come loose or is blocked