Hello,

             My daughter inherited a lovely Fiesta but it overheats (intermittently) no common reason or consistancy so dont think its the head gasket..   I started to have a look and have ended up with the top end stripped as the cam belt looked ropey and it had an oil leak from the rocker cover.

I have changed the thermostat which made no difference and wondered from watching Mr Google whether it has ??   a heater control valve as some of the videos say that this can cause overheating if the bypass to it is blocked.  Well I stripped out the numerous bits of plastic only to find the two matrix element pipes go into the bulkhead and not via this little valve that is on all of the videos.    Does the Mk6 1.25 have one I wonder.

Any help be appreciated.

                                                            Thanks  Col.

Too late now, but it might have been a good idea to do a 'Hydrocarbon gas test' on the cooling system before pulling the head off.

Is the car back together and running now ?

If so get a hydrocarbon test and check the cooling system.

Was the radiator fan coming on ? 

14 hours ago, isetta said:

Was the radiator fan coming on ? 

Hello Thanks for the replies. I am going to get back too it at lunchtime if the rain eases 😞  Yes rad fan comes on and I have flushed the rad too. Its the blooming intermittancy of it that is baffling me     Still cannot find this heater control valve but looking at Mr You tube a chap joined the two heater feed pipes with a bit of copper pipe to bypass it as a tester so can do that 🙂

One chap also said it was critical to bleed any air locks out of the water system but I have never heard of that one.

 

Thanks again,   Col.

If you have air trapped in the system then the car will overheat, I would from cold, have the heater on full hot, the tank cap off and run the car for a while 20 minutes, that should be sufficient to get rid of any trapped air, you will know if there is trapped air as the water in the reservoir will bubble while there is no heat in the system

On 5/6/2022 at 3:09 PM, Neb_engineer said:

If you have air trapped in the system then the car will overheat, I would from cold, have the heater on full hot, the tank cap off and run the car for a while 20 minutes, that should be sufficient to get rid of any trapped air, you will know if there is trapped air as the water in the reservoir will bubble while there is no heat in the system

Hello,

             Thanks all for the comments.  I am ashamed to say that the car has been on my drive since May.   I just have got some time to get back too it. I have all but rebuilt the engine it was in a terrible state the rocker cover gasket leaking oil into the plug tunnels etc etc.

              I have read that there is a heater bypass valve but you know I cannot find one the heater feed pipes go straight through the fire wall into the heater matrix so I guess thats one thing less to check?

             Back to it tomorrow I think just finish the rebuild and see how she goes paying attention to the air locking.

 

                                                                     Thank you,  Col.

It might lack that heather valve. Pipies come straight in to matrix and the heat is blocked by an flap.  It might be a  blocked matrix, pipes. 

Hello Chaps/Chapess's  🙂

Back onto the daughters Fiesta....  My Xtype blew up (injectors)   Then my blooming Transit which was also overheating. Replaced the head (it was cracked) but still exhaust like a kettle only to find it was the EGR cooler.   Done 200 miles so hoorah.

Rebuilt the fiesta and she started first time.    Ran her for an hour at tickover and all ok but then started to blooming overheat.   Will try the air lock trick above in a mo. Looking like the flipping head might try some K seal tomorrow ??

 

Any thought appreciated.                                Thank you   Col.

On 9/28/2022 at 6:10 PM, Colin Kilner said:

Hello,

             Thanks all for the comments.  I am ashamed to say that the car has been on my drive since May.   I just have got some time to get back too it. I have all but rebuilt the engine it was in a terrible state the rocker cover gasket leaking oil into the plug tunnels etc etc.

              I have read that there is a heater bypass valve but you know I cannot find one the heater feed pipes go straight through the fire wall into the heater matrix so I guess thats one thing less to check?

             Back to it tomorrow I think just finish the rebuild and see how she goes paying attention to the air locking.

 

                                                                     Thank you,  Col.

Hello,

               Just trying this and found the top bleed valve thing on the rad.. There was a bit of air bubbling into the resevoir along the skinny pipe from the head but stopped now.     Ticking over beautifully and now at 90 degrees    No steam out of the back no oil in water or water in oil .     Bothe heater matrix pipes hot and all hoses hot apart from the bottom radiator one that is quite cool !!!!!!!??

 

Fingers crossed    

                                                             Col.

Hello,

            Thought that I would update after another day pottering on her 🙂

Bled the radiator and ran it with the cap off. Lots of air coming along that top pipe from the head so much i thought blimey must be a breach but eventually stopped helped by some frantic hose squeezing 🙂 🙂 

I was worried about the lower radiator hose not getting hot but eventually it did just as the fan cut in.

I have treated myself to a fancy diagnostic. The bottom hose gets hot pretty much at the same time as the fan cutting in at 105degrees and fan turns off when its dropped to @99/100 degrees.  My initial thought was that is quite late????    everything is new water pump thermostat/housing but of course they are mass produced.

Thanks for everyones help cheers.    Must be able to find the thermostat spec somewhere 

 

                                                             Col.

18 minutes ago, Colin Kilner said:

Must be able to find the thermostat spec somewhere

Thermostat operates at 106C

Hello all,

                     Thank you so much for the posts/assistance.   My goodness nearly at that reach for the matches point 🙂

Thermostat working ok drives for about 10/20 miles great lots of power no steam out of the exhaust no oil in water /water in oil and then overheats.  Think head gasket/head is ok surely if not it would fail before 15 miles?  I have done a expansion tank test and it says ok 🙂

Changed the radiator now as i flushed it and got calcium stuff out. Thought that I had cracked it and nope after ten miles overheats she goes.

My mechanic friend is also foxed.   Water pump looks new but ive not changed it yet I recon that is tonights job.  Do they ever fail on the shaft like my Transit did years ago???   Only other thoughts is clogged waterways in the block??  or some clown has left something in a waterway (plastic bag bla bla)   Now I am desperate.

 

Any thoughts be appreciated.

 

                                        All the best,   Col.

Edited December 7, 20223 yr by Colin Kilner
Cannot spell.

I have replaced countless radiator caps on these for similar issues, sometimes it can be the most obvious fixes, if you haven't done this already its worth a go. Also the bottles suffer from hairline stress cracks

Thanks for the message,

                                                   My girlfriends son has the same car and we borrowed his cap to try but nope got about 8 miles and up it went limped home.

 

One thing I notice the heater blowers blow hot when you rev it but cool when on tickover. Could that be a circulation problem ??  I dont think the engine cooling on these rely on heater matrix flow ??   Guess I could bypass it 🙂  🙂 

Its a new water pump but i guess they fail. Got all the pulleys off and dont know whether to take it off. Such a pain releasing the timing chain tensioner !!  Someone said that if you take the thermostat housing off and feel inside you can feel/hold the water pump impellers and so if to turn the pully at the same time you can see if its failed on the shaft.So blooming fed up with this one so wanted to let her have it for her birthday peresent 😞 

 

                                    Really appreciate any ideas chaps 

                                                                                                           Col. 

Does it actually boil over or is it just the gauge telling you its over heated.

Whats the live data temp say when it over heats?

Many, many years ago I had a car with the same sort of random overheating problem, which from your description would seem to have been the same. Like you I replaced just about everything, except the actual engine. I even took the cylinder head off. Very sad to say in the 3 years I owned it the problem was never I identified.

I would like to be able to suggest something for you to try, but it does seem that you have covered 95% of the possible causes. You could take it to a garage that has the equipment to vacuum fill the cooling system which should eliminate any possible air locks.

On 12/9/2022 at 1:21 PM, Ecosport2019 said:

Does it actually boil over or is it just the gauge telling you its over heated.

Whats the live data temp say when it over heats?

Hello,

               Thanks for the reply.   Yes she actually overheats hubble bubble etc etc etc 🙂  🙂     Expansion tank makes Beethoven symphony noises so yes I am with you is it a faulty sender etc.   Took water pump off this morning and looks fine not slipping on the shaft.     Got one on its way as read about "lazy" water pumps. Going to swap the stretch belt as well as the chap at Euro said he has known them slip without any noise 😞       Also going to put some rad flush through it in case the head/block waterways are restricted. 

                 I said to my mechanic friend that I was going to take the head off but he/we think its a lot of work and unlikely a problem if that was a problem with this engine it overheats on the drive not after 20 miles     Fair shout i recon?? 

                 Any further thought Id be so grateful it would be lovely to get the daughters car to her for Christmas.

 

                                                         All the best,    Col.

Yeah i agree, the only other thing that i know is a hairline split that appears at the seam of the expansion bottle, it only shows its face at a certain point and then it instantly changes the boiling point as the pressure changes.

I know it's a pain but if i remember  a new bottle and cap was around £30 from ford but that was a few years ago.

You could always swap it from your other car.

21 hours ago, Ecosport2019 said:

Yeah i agree, the only other thing that i know is a hairline split that appears at the seam of the expansion bottle, it only shows its face at a certain point and then it instantly changes the boiling point as the pressure changes.

I know it's a pain but if i remember  a new bottle and cap was around £30 from ford but that was a few years ago.

You could always swap it from your other car.

Happy Sunday,

                                Goodness that is a good point I will check that today when she overheats then you expect a bit of stean from the expansion bottle so it may be masked..

Thanks for the suggestion.

 

                                                                                                   Col.

Hello Chaps,

                        Always like to report back.   New water pump etc etc no great difference.   So started to flush he through the heater matrix.

Got out a good egg cup full of calcium etc.    I recon she is blocked up in the head/engine.

Ran a Euro rad flush through and then drained/refilled.     Been for a test run and gave her some stick.  She still overheats but as it rises if I turn the blowers on full and heater hot it brings it down from melt down and eventually drops to normal. 

Going to flush her to death again tomorrow but I wonder what the strongest system flush us that you can get?      Any experience out there??

I think someone put some sealer in her just before we bought her as the thermostat housing had a split in it which i changed.

 

                                                 Thanks as always,    Col.