Hi All

trying to systematically work through some issues I have with my recently purchased 1992 Ford Sierra Ghia Hatchback.

It's a 2.0i DOHC EFI 8V that I bought and imported from Spain start of march and had shipped to Ireland via way of the UK.

It briefly overheated on the drive from Dublin to where I live so allowed it to cool sufficiently before getting it home.

I'm knowledgeable with cars rebuilding and modifying Volvo 855 AWD's and S70 T5's are my drug of choice.

However, this simpler motor has me scratching my head.

Whenever I get a car I do a full stage zero service - replacing all parts that will likely go wrong such as water pump, alternator, belts, thermostat, thermostat housing, coolant, oil, oil filter, pollen filter, fuel filter to name a few things.

I've flushed the entire system, thoroughly, disconnected all coolant pipes, even descaled the engine block, heater matrix, radiator system and the car initially went from blowing hot/cold to hot when running the internal cabin heater at hot.

The over pressurization is now back and the initial hot to cold to hot issue is back and I've noticed that the coolant is being pushed through the expansion tank cap.

There is no water-oil mixing going on and head gasket sniff test is not showing a damaged/leaking gasket.

totally baffled by this so anyone experience the same issue?

 

Mine did this and it turned out that I did not have a pressure release valve on the expansion bottle, it may be worth checking that you one and it is working.

Failing that look for some of the waterless stuff as it doesnt pressurise.

 

Thanks for your reply Caddyshack.


Where is the pressure release valve?

The weird thing is that when the engine runs on idle, the water flows from the thermostat housing into the top of the expansion tank. I'm using pre-made coolant (not added any water to it). when the car is taken for a drive and the bonnet is opened, the expansion tank is empty. however, leave the car for 20 mins (engine off) and the tank is full again (only noticed that the coolant leaks through the expansion cap when driving more than 40 miles or more.

also, if you gradually bring the rev's up to 2500 using the accelerator, the coolant is sucked into the lower pipe until the expansion tank is empty. (this is despite the bottle being full to the maximum mark when cold).

when the liquid returns the air gurgles through the system.

An interesting dilemma.

As the car was brought in from spain and the thermostat had been encrusted with heavy limescale, my thoughts are of is there or could there be a calcium carbonate build up somewhere in the head that is restricting the flow of coolant around the block?

There are no unwanted knocks, piston slap or tappet noises and the oil is good as I flushed the engine with 5 litres of oil before I did the final oil change.

 

Asduming you've changed the thermostat 3 things off the top of my head
For did a recall for the water pump pipes which swapped the flow pipes around on the pump, it might have had a different pump fitted at some point
The fans don't work, spin them both to see if they aren't seized and then power them up from the fan switch on the thermostat housing
The switch may have failed as it's designed to work at 100/110 if it's the grey one
The green one fitted to the diesal version kicks in lower and then the one you want is red and was a Mondeo fitment

 

It sounds like the head gasket has gone. Mixing oil and water only happens when it's leaking between the oil and water connections, but there is only one oil way through the head gasket and there are several water ways. So the chance of having oil and water mix in case of head gasket failure is not really that great.

The pressure relief valve is in the cap of the header tank and apparently it is working as it is sometimes pushing coolant out.

If it's not the head gasket it could still be that there is a lot of air in the cooling system. The DOHC cooling system is not that easy to bleed. There is a hose coming from the heater matrix going above the exhaust manifold, and because the hose runs very high, air can stay inside this hose. If you tie-rap the hose at a lower location the air is able to flow out.

 

See replies highlighted in bold print.

Have you a part number for the mondeo version and where is it situated?

Cheers

 

Interesting information there I'll look into tying the water pipe onto a lower level.

Cheers