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Overheating - Suspect Thermostat

#1 User is offline   IanClements 

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Posted 29 March 2015 - 07:36 PM

Have been monitoring my engine temp recently with the ODB2 kit and found that my engine (1.6) tends to run hot and have seen temps over 120 degrees when driving normally with the fan kicking in a lot, the guage stays normal though it drives OK. Anyway, so far I've changed the water pump, HCV and expansion tank cap, all of which needed doing but despite three coolant changes I still have the same problem. If I feel the two pipes going into the thermostat housing I find that one is hot and the other cold, does this sound like the thermostat sticking closed? Radiator is stone cold even though the top hose is hot, bottom is cold.

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 User is offline   nottadam 

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Posted 29 March 2015 - 08:36 PM

Hi
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
Posted Image

This post has been edited by nottadam: 29 March 2015 - 08:42 PM

FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#3 User is offline   IanClements 

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Posted 29 March 2015 - 08:41 PM

Great reply and nice diagram. Sounds like I need to order a housing as well then by the sound of things.

#4 User is offline   nottadam 

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Posted 29 March 2015 - 08:51 PM

Yes mate, your local garage mechanic is correct. Also the new housing will come with a sealing gasket, the old one will be compressed and may not seal correctly.
Genuine Ford ones are not cheap though, not much change from 40 quidPosted Image.
Paul
FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#5 User is offline   IanClements 

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Posted 29 March 2015 - 08:55 PM

40 quid's not too bad I guess, there's some dirt cheap ones on ebay I can see, will probably stay genuine unless I can find a decent brand. Do you know if the club has any discount agreement with Ford for a bit off?

#6 User is offline   nottadam 

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Posted 29 March 2015 - 09:01 PM

No discount that I know of through the club.
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
FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#7 User is offline   IanClements 

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Posted 03 April 2015 - 04:57 PM

Fitted the new thermostat and housing today, I tested the old one and it's definately stuck so worth doing. All hoses are now hot but surprisingly the engine temp is still high at around 118 degrees average; there might still be airlocks in the system so just going to drive it for a few days. I noticed that the radiator stays cold but not sure whether that's normal or not to be honest.

#8 User is offline   happy-kat 

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Posted 03 April 2015 - 07:29 PM

Have you carefully squeezed the main fat pipe? When cold engine
searching is fruitful | I'm a sponge not a mechanic | please do try that if stuck with a Puma problem whilst waiting for a reply | For the Puma fan this read 'The Inside Story Book' is very nice to own sometimes still seen for sale

#9 User is offline   IanClements 

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Posted 03 April 2015 - 07:36 PM

I squeezed the hose that goes from the right hand side of the block to the top of the rad, seemed to get some gurgling sounds out of it.

#10 User is offline   happy-kat 

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Posted 03 April 2015 - 09:01 PM

Could be an air lock, we had one in the other car and a good few squeases helped move it and then the coolant level went down we felt we had got rid of it.
There is probably a proper technical description somewhere.
searching is fruitful | I'm a sponge not a mechanic | please do try that if stuck with a Puma problem whilst waiting for a reply | For the Puma fan this read 'The Inside Story Book' is very nice to own sometimes still seen for sale

#11 User is offline   nottadam 

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Posted 03 April 2015 - 09:26 PM

You should be able to feel heat in the radiator and both top and bottom hoses when the engine is up to temperature and the thermostat has opened.
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


FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#12 User is offline   IanClements 

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Posted 03 April 2015 - 09:34 PM

Thanks Paul, have bled the system as best I can using other posts I found on the forum. Think I need to monitor it for a few days and keep checking on the rad.

#13 User is offline   IanClements 

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Posted 05 April 2015 - 10:35 AM

OK, so I went out last night and did a few miles of motorway driving, when I was close to home the gauge moved for the first time and showed it overheating, just managed to park up in time I think. Looking at it now the coolant level hasn't dropped at all so I'm assuming no airlocks left but I noticed that my car seems to have two radiators one behind the other which I assume is for the aircon. Feeling the rear one it's getting warm but it's the front that stays cold so is this OK?

Can't understand why it's overheating now and all the pipes are warm or hot.

#14 User is offline   nottadam 

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Posted 05 April 2015 - 04:18 PM

Yes, the engine coolant radiator is the one on the inside nearest the fan. Did you bleed the system with temperature control set to hot?
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
FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#15 User is offline   happy-kat 

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Posted 05 April 2015 - 07:28 PM

Great post when next on my pc I will (how you don't mind) tack that onto the bleeding guide in the wiki
searching is fruitful | I'm a sponge not a mechanic | please do try that if stuck with a Puma problem whilst waiting for a reply | For the Puma fan this read 'The Inside Story Book' is very nice to own sometimes still seen for sale

#16 User is offline   nottadam 

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Posted 05 April 2015 - 08:01 PM

Thanks Kate.
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

FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#17 User is offline   IanClements 

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Posted 05 April 2015 - 08:04 PM

Thanks Paul, if the heater matrix was blocked would turning the control to cold allow the coolant to flow normally? I tried it but it didn't make a difference. Am I right in assuming that any airlocks in the system should work their way out of the system fairly quickly?

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 User is offline   nottadam 

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Posted 05 April 2015 - 08:57 PM

Hi Ian
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
FRP#008, 2001 1.6 Med Steel Blue, Fiesta 1.5 TDCi Zetec S

#19 User is offline   IanClements 

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Posted 05 April 2015 - 09:04 PM

I replaced the HCV last weekend unfortunately. Going to try your trick of leaving the cap off overnight.

#20 User is offline   IanClements 

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Posted 06 April 2015 - 11:35 AM

Still having problems. Left the cap off overnight and it didn't make a difference so I put the back end up on ramps and tried to bleed it again. It didn't make any difference but I noticed that both hoses to the rad got hot as did the rad itself so I put the air con on for a test (it works!) and the fan cooled the radiator back down. However, the bottom hose was still hot which suggests to me that coolant is just not circulating so there must be a blockage. Looking at the diagram, even if the heater matrix was blocked I would have thought there should still be a flow of coolant through the rad as it's on a separate loop. If I squeeze the top hose the level in the expansion tank rises, does this mean that the rad is OK?

Getting desperate but don't know what to try next.

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