Our elderly '94 Mondeo 2.0 petrol is overheating, but not losing water. Seems OK on several longish runs then symptoms reappear. Symptoms are after running for some time or idling for a few minutes; temp gauge creeps towards red, heater goes cold if set to hot. Stopped immediately and checked under bonnet; header tank is full almost up to cap, no signs of leak. After leaving for a few minutes then gently realising presure, water level drops back to 'max' line. Tonight I managed to get home keeping an eye on temp gauge, but motor was really cooking when I stopped and water boiling (?) in system. Header tank cap was realising pressure.
System was pressure checked OK the last time it occurred. Garage suggested may be head gasket on way out. No sign of water in oil; oil level constant.
(Heater has never been very efficient)
Could this be stuck thermostat? Any help appreciated.
Mark (Aberdeen)
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You didnt mention whether the radiator cooling fan comes in?..As temp goes above normal. fan switch should kick in and turn fan on. cooling system down to normal..
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Steve
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The heater going cold suggests an air lock.
I'd get an MOT garage to 'sniff' the header bottle with their gas analyser and see if they can detect any combustion gases - it does sound like the early stages of a head gasket.
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Fan comes on OK, and all hoses and radiator seem hot, suggesting normal flow of coolant. Last garage visit for the problem suggested head gasket with leak into exhaust which may explain clean oil and no (visible) oil in coolant.
Really weird that coolant level stays same for weeks.
Thanks for help guys.
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Would agree with Marlot..
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Steve
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Added approx 1 litre of water to header tank to bring it back up to 'max'. Oil still OK no sign of water. Still no sign of water leak. Did short distance tonight and noticed thermostat opening OK.
If air lock, where is best point to try and bleed system?
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Why not just drain, flush, and re-fill the cooling system? It hardly costs anything and you seem knowledgeable enough to do it easily. While you're at it you could test the thermostat on the hob, and renew if necessary. Simple things first I always reckon.
Once you're satisfied with the state of the cooling system, if the problem persists then it's time to think about the head gasket.
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Make sure the radiator is not partially blocked could give these symptoms - try feeling the front of the rad when the engine is hot - are there cool spots at certain points - if so it is blocked - furred up?
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If air lock, where is best point to try and bleed system?
I don't know this particular motor but I would guess there will be bleed valves somewhere on the heater hoses. Have a look along the hoses for something that looks like a strap round the hose with a wheel/thumbscrew on it.
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As a matter of interest.How are you checking stat opening? best way is to open bonnet.leave engine at idle. then wait for top hose to warm up. If it does so slowly then stat sounds ok..If top hose remains cold for a long time. then suddenly gets hot. it will be the stat staying closed too long.
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Steve
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Had the joy of owning a 93 Mondeo a good few years back - it developed a similar prob after I changed the thermostat. The correct thermostat has a small hole at the top of the outer body, which has a small metal "tag" inserted through it. I replaced it with a motor factors one without the hole and tag, which Ford later told me was a common error and a major no no.
A short time later the head gasket went - Couldn't prove the two were related, but have my suspisions. Pull the thermostat housing apart - on three bolts if I recall correctly at the end of the top hose - you will need a new gasket to seal the housing again and new coolant - may be worth checking esp if you are going to drain down the system anyhow.
Leon
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Leon, thanks for that info. I had the thremostat changed at the last but one major service; sounds remarkably similar.
Latest development confirms my suspicions. Drove to supermarket yesterday, 10 mins, parked up and left ticking over, checked under bonnet but also clocked the amount of steam coming out of exhaust; definately head gasket I would think. More steam than Flying Scotsman now combined with lumpy tickover.
Sad because she still starts and drives OK. Hopefully will get SWMBO to work and back (5 miles) for a few days.
Not worth repairing; trade in from Fords of Winsford was only £200 before the head gasket!! Only 2 owners from new.
Advertise for spares?
Thanks for all help.
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Definitely a headgasket - had the same symptoms on a 92 Sierra 2.0 DOHC. Dump the car or get a cheap engine; I repaired mine twice - waste of time; the replacement engine (£165 + VAT) has worked perfectly for two years and uses no water. Replacing the headgasket would have cost £500 plus.
Cheers
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