Overheating - Suspect Thermostat
#1
Posted 29 March 2015 - 07:36 PM
I only ask because it doesn't look like an easy job so could do with someone agreeing with me before I do it. My local garage told me the housing's tend to crack when you take them off also so best to replace that as well.
#2
Posted 29 March 2015 - 08:36 PM
I have the same issue with the wife's 1.6.
Fan comes on quite often, even when not stuck in traffic etc. Guage never above halfway.
I'll be doing this job soon, I have a new housing and stat ready to fit.
Hardest part of the job is actually getting to it. Alternator needs to come off, which means auxillary belt has to come off, which means OS front wheel needs to come off to access belt tensioner.
From what you say it does look like your thermostat is not opening. The pipe which you say gets hot I suspect is the smaller one which comes from the HCV. Coolant is always free to flow through this loop via the HCV, and it sounds like this is the only cooling your engine is getting.
The thermostat should open to allow coolant to flow through the main radiator 'loop'. I did this diagram to help me understand what is happening, it may help you.
The coolant temperature sensor, which tells the ECU when to turn the fan on and off, is located in the cylinder head between plugs 2 and 3, unlike the 1.7 which is located in the housing under the coil pack.
Paul
This post has been edited by nottadam: 29 March 2015 - 08:42 PM
#3
Posted 29 March 2015 - 08:41 PM
#4
Posted 29 March 2015 - 08:51 PM
Genuine Ford ones are not cheap though, not much change from 40 quid.
Paul
#5
Posted 29 March 2015 - 08:55 PM
#6
Posted 29 March 2015 - 09:01 PM
You could always ask at your local parts desk for a discount, you never know.
I bought one of these
http://www.fordparts...93599_c_994.htm
Bought a few bits from here and never had any problems.
Paul
#7
Posted 03 April 2015 - 04:57 PM
#8
Posted 03 April 2015 - 07:29 PM
#9
Posted 03 April 2015 - 07:36 PM
#10
Posted 03 April 2015 - 09:01 PM
There is probably a proper technical description somewhere.
#11
Posted 03 April 2015 - 09:26 PM
If you can't, then coolant is not flowing as it should.It's difficult getting the air out of this cooling system and there are differing opinions on the best way to do it.
I would normally run the engine up to temperature with the expansion tank cap off and the car parked in such a way that the expansion tank is the highest point.
It does help to keep squeezing the hoses during this time also.
Keep the level in the expansion tank topped up if it goes down.
If possible leave the cap off overnight to allow more air to escape. And keep a check on the level for a week or two afterwards.
Paul
#12
Posted 03 April 2015 - 09:34 PM
#13
Posted 05 April 2015 - 10:35 AM
Can't understand why it's overheating now and all the pipes are warm or hot.
#14
Posted 05 April 2015 - 04:18 PM
Cooling system faults are one of the most difficult things to diagnose and you may have to finish up changing just about everything to fix it.
This is how a normal, healthy system should work, refer to the diagram...
On a cold start up the thermostat is closed so preventing the flow of coolant from the radiator bottom hose back to the head.
Coolant is pumped around the 'small' loop to the right hand inlet of the HCV.
Then, depending on the position of the HCV, it will flow directly back via the left hand pipe or, if heater control is in the 'hot' position, through the heater matrix and then back via the left hand pipe. BUT, if the heater matrix is blocked or is airlocked, this will not happen. BLEED THE SYSTEM WITH HEATER CONTROL SET TO HOT.
With the engine idling, you should feel the right hand hose getting warm before the left one. Eventually, after about 10 mins, both hoses will feel quite hot, the left hand one all the way to the thermostat housing. This is enough to keep the engine at normal operating temperature for quite a while when just idling. You will also feel the radiator top hose (the right hand one) getting warm but this is just heat convection from the outlet at the right hand end of the head.
Eventually the thermostat will start to open and you should feel the top hose getting hotter, then you should feel the radiator getting hot, but due to the efficiency of the radiator the bottom hose may still be cool.
If you look closely at the HCV in the diagram you can see that in the 'hot' position, coolant can only go through the heater matrix, so if it is restricted it will affect the temperature of the coolant which the sensing side of the thermostat sees. This can cause strange symptoms.
I hope this will help with your diagnostics.
Paul
#15
Posted 05 April 2015 - 07:28 PM
#16
Posted 05 April 2015 - 08:01 PM
The described operation of the cooling system may not be perfectly correct, but in the absence of any other descriptions, it is an attempt to clarify the apparent mysteries of the Zetec engine cooling system.
Anyone with any more experience and/or corrections is welcome to add their comments.
Paul
This post has been edited by nottadam: 05 April 2015 - 08:02 PM
#17
Posted 05 April 2015 - 08:04 PM
I've always bled the system with the heater on hot but will try again tomorrow. Do you know of any write-ups on flushing the matrix, I haven't found any yet?
#18
Posted 05 April 2015 - 08:57 PM
The answer to your first question is yes, the gate valve will move to block the flow to the heater matrix, opening the flow back to the thermostat housing.
The answer to your second question is yes and no.
I have seen forum threads where people have been faffing about for ages trying to get air out.
I replaced the stat on our 1.6 last week, I had problems actually getting the coolant in! I had to remove the small hose from the expansion tank (the one which goes to the left side of the radiator) and blow down it to get the air moving and coolant to go from the expansion tank.
When I was happy that I had put back in approximately what I had drained out, I ran it up to temperature with the cap off and left it off overnight. Next day the level had dropped about an inch. Topped up and it seems fine now.
I doubt it will be your heater matrix. The most likely culprit if it doesn't settle down will be the HCV. They can do weird things when they go faulty. Have you any record of it being replaced?
Paul
#19
Posted 05 April 2015 - 09:04 PM
#20
Posted 06 April 2015 - 11:35 AM
Getting desperate but don't know what to try next.