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Thermostat?

6K views 24 replies 7 participants last post by  yeah right 
#1 ·
For the last few days, when I drive the car in the morning when it is cold, after the first few kays, the temp gauge rises almost to the red before the thermostat cuts in and it drops back to normal....the temp never goes this high any other time, only first drive in the morning, when it is at its coldest.
Is this the thermostat that is buggered or what?
Thanks
 
#8 ·
Thanks for the comments guys, I've gone and bought a Trident thermostat, with lower temp the 180deg one after advice from gmdestroya. I'll install it Monday or Tuesday and see how it goes. I believe this is the same reason that i am leaking coolant allthe time, there have been several long pressure tests, no problem found... I believe that during the time the temp goes up to just below the redline that the coolant temp gets so hot and goes out of the overflow. Makes sense to me that it may be the mysterious source of my loss of coolant, lets hope so.
 
#9 ·
gmanEA said:
Thanks for the comments guys, I've gone and bought a Trident thermostat, with lower temp the 180deg one after advice from gmdestroya. I'll install it Monday or Tuesday and see how it goes. I believe this is the same reason that i am leaking coolant allthe time, there have been several long pressure tests, no problem found... I believe that during the time the temp goes up to just below the redline that the coolant temp gets so hot and goes out of the overflow. Makes sense to me that it may be the mysterious source of my loss of coolant, lets hope so.
If the coolant goes out the the overflow when hot, it should get drawn back through the one-way valve in the cap (not the springloaded seat - thats the way OUT of the cooling system) and then back into the engine when it cools. Or it may be leaking past the cap top seal & running down the tank.

Check the tiny cap check-valve to ensure the coolant can get back into the engine and the upper seal on the cap to make sure it's a good tight fight to the neck.
 
#10 ·
yeah right said:
If the coolant goes out the the overflow when hot, it should get drawn back through the one-way valve in the cap (not the springloaded seat - thats the way OUT of the cooling system) and then back into the engine when it cools. Or it may be leaking past the cap top seal & running down the tank.

Check the tiny cap check-valve to ensure the coolant can get back into the engine and the upper seal on the cap to make sure it's a good tight fight to the neck.
I think that it is coming out of the overflow next to the cap in the upper reservoir where you put the coolant in. The tubing for the overflow is about 50cm long and leads down towards the ground where it would go out onto the ground, no way for it to go back into the engine...

I once stopped the car and got out to see a lot of coolant pooring out and it did appear to be coming from around the region where the overflow is, but I did not have the bonnet open to see exactly where.
 
#11 ·
gmanEA said:
I think that it is coming out of the overflow next to the cap in the upper reservoir where you put the coolant in. The tubing for the overflow is about 50cm long and leads down towards the ground where it would go out onto the ground, no way for it to go back into the engine...

I once stopped the car and got out to see a lot of coolant pooring out and it did appear to be coming from around the region where the overflow is, but I did not have the bonnet open to see exactly where.
Ah - forgive me - I'm not overly fammilar with E-series - they don't have a cap on the radiator do they? (checked your pics & the seems to confirm my suspicions!!) So effectively the "overflow" isn't really an overflow - it's more of a buffer with an air pocket accumulator. You haven't overfilled it have you cos that would cause it to flow out onto the ground?

I'd be inclined to check the cap on there as it's performing the same function as a normal radiator cap - just in a different location.
 
#12 ·
yeah right said:
Ah - forgive me - I'm not overly fammilar with E-series - they don't have a cap on the radiator do they? (checked your pics & the seems to confirm my suspicions!!) So effectively the "overflow" isn't really an overflow - it's more of a buffer with an air pocket accumulator. You haven't overfilled it have you cos that would cause it to flow out onto the ground?

I'd be inclined to check the cap on there as it's performing the same function as a normal radiator cap - just in a different location.
Nope, I havn't overfilled it, i have to refill it every few days because after a few days the coolant isn't visible anymore and the "coolant low" light comes back on. The radiator cap is not suspect, I have replaced it to ensure that...
 
#13 ·
Hmmm - I hate to say it - but it sounds like a head gasket or corroded head - how long after you stop a hot engine does the pressure remain - should be about 10-15min max. Any more than that & it's getting compressed air in the system - most likely 180 PSI air from the combustion chamber. I can't see the thermostat being the problem - I mean it would be unusual to the coolant to flash off as steam unless there was low pressure in the cooling system and since the pressure tests have said there are no leaks and the cap is new that rules that out.
 
#14 ·
yeah right said:
Hmmm - I hate to say it - but it sounds like a head gasket or corroded head - how long after you stop a hot engine does the pressure remain - should be about 10-15min max. Any more than that & it's getting compressed air in the system - most likely 180 PSI air from the combustion chamber. I can't see the thermostat being the problem - I mean it would be unusual to the coolant to flash off as steam unless there was low pressure in the cooling system and since the pressure tests have said there are no leaks and the cap is new that rules that out.
Oh boy, I really hope not. There are no typical signs of head gasket problems (exhaust smoke is clear, oil clean and oil cap, coolant stays correct colour etc) but its not something i want to have happen same as rest of us...

How do I check the pressure remaining after stopping a hot engine ??? Im newbie mechanic lol.

Anyhow, on Tuesday I will be putting in the new thermostat, Ill attach a small bottle to the end of the overflow tube and then monitor things from there. If coolant ends up getting in the bottle then we know that its where the coolant is going missing and just have to figure out why, if I stop losing coolant after the thermostat change then lucky me heh. But it has been a real headache indeed.
 
#15 ·
gmanEA said:
Oh boy, I really hope not. There are no typical signs of head gasket problems (exhaust smoke is clear, oil clean and oil cap, coolant stays correct colour etc) but its not something i want to have happen same as rest of us...

How do I check the pressure remaining after stopping a hot engine ??? Im newbie mechanic lol.

Anyhow, on Tuesday I will be putting in the new thermostat, Ill attach a small bottle to the end of the overflow tube and then monitor things from there. If coolant ends up getting in the bottle then we know that its where the coolant is going missing and just have to figure out why, if I stop losing coolant after the thermostat change then lucky me heh. But it has been a real headache indeed.
I hope not too - for your sake - but it's not sounding good. Do the thermostat (sounds like it needs doing anyway) and go from there - but I very much doubt it'll make any difference to the coolant disappearing.

Just squeeze the main hoses to check the pressure - or slowly remove the cap - should only be a small hiss. If it bubbles much there's problems.

Head gaskets don't necessarily show as one of the typical symptoms - I know - 3 months ago I had the exact same thing you are experiencing (except for the temperature spike) and it was the head corroded in the water passage where it contacts the gasket behind no.6 cylinder. The high pressure charge in no.6 was forcing it's way past the gasket into the cooling system. The oil was perfect - no milk - no smoke - coolant was bright green - but it was blown - big time. Even a tee-kay check showed nothing until it got so bad the air was bubbling through the overflow tank when you opened the cap on the radiator up to 1 hour after stopping!! Have a sniff in the overflow - if it has the odour of exhaust gases you'd better start saving!

In mine coolant was disappearing at a phenomenal rate but there was no sign of where too. Sound familliar? lol
 
#16 ·
yeah right said:
I hope not too - for your sake - but it's not sounding good. Do the thermostat (sounds like it needs doing anyway) and go from there - but I very much doubt it'll make any difference to the coolant disappearing.

Just squeeze the main hoses to check the pressure - or slowly remove the cap - should only be a small hiss. If it bubbles much there's problems.

Head gaskets don't necessarily show as one of the typical symptoms - I know - 3 months ago I had the exact same thing you are experiencing (except for the temperature spike) and it was the head corroded in the water passage where it contacts the gasket behind no.6 cylinder. The high pressure charge in no.6 was forcing it's way past the gasket into the cooling system. The oil was perfect - no milk - no smoke - coolant was bright green - but it was blown - big time. Even a tee-kay check showed nothing until it got so bad the air was bubbling through the overflow tank when you opened the cap on the radiator up to 1 hour after stopping!! Have a sniff in the overflow - if it has the odour of exhaust gases you'd better start saving!

In mine coolant was disappearing at a phenomenal rate but there was no sign of where too. Sound familliar? lol
Yep sounds very familiar, I'd definitely call it a phenomenal rate. Im estimating 250-500mL on a normal driving day (to the city and back, maybe a little around home). Im in Bendigo at the moment, what I'll do is this on your advice, after driving home I'll wait for 30 mins and then ill squeeze the hoses, if they are hard ill know theres a fair bit of pressure, ill remove the radiator cap and if its more than a small hiss then we'll know there are problems...

After that I'll report my findings, that will be Monday. I'll be doing the thermostat either Monday or early Tuesday... So late next week should have done a few tests to help determine this problem. Thanks for your help mate.
 
#17 ·
Ok, after my 2hr drive from Bendigo to Melbourne I waited for nearly 45mins and tested the pressure, hoses were fairly tight still and when I took of the radiator cap the coolant came up some out of the overflow and some into the towel that I was opening the radiator cap with, so quite a lot more than a little hiss. I'm yet to replace the thermostat but I bought the thermostat gasket on the way home and I'll do that either today or tomorrow morning.
 
#18 ·
45 mins is a long time - I'd say it's a pretty certain gasket job. What happens is the pressure only rises in the cooling system for 2 reasons - the pump and the water expanding as it heats. When the engine is stopped the water cools quite quickly - it's still hot but in the area around the cylinders which are no longer creating heat the temperature drops rapidly - and as it cools it contracts and the system pressure drops. What it is doing in your case is the pressure is not water pressure - it's air pressure from the leak from the cylinder to the cooling system - and the air being a gas is compressible - and so therefore remains at a pressure equivalent to the cap pressure rating (normally just over 1 bar or 14 psi) which is why the hoses still feel really solid even after the engine cools - the air doesn't contract.

When you do the thermostat gasket be sure to refill with the heater valve open (ie hot air to the cabin - you don't need the fan on or anything - just set it to hot) and use any bleeders it has to get the air clear out of the head. I'm not really familliar with these engines (although a friend of mine just bought a EFII Fairmont here in NZ - I can look to see what the arrangement is there next time I see him) so I can't tell you where the bleeds will be - but they will be near the highest point of the head itself - either in the form of a BSP allen socket plug or a bolt with a nipple on the end within a bolt - perhaps on the thermostat housing like my XF.

It's a pain in the ass having to get a head gasket done. Make sure you get QUOTES not "estimates" if you're not going to do it yourself. A lot of places here in NZ are initially reluctant to give a "quote" because they think you are expecting it for that price no matter what they find once they start. But if you explain to them you want an itemised quote for the cost of the job that they would normally expect to have to perform in that situation with anything unusual as an extra it makes them more comfortable about a quote. I mean they know how long it takes to remove and install - they know the cost of parts that they MUST replace. What they don't know is the condition of the head itself - so get a price for welding, pressure & crack testing etc as a extra (it's most likely corroded so it'sll just be the welding - but it is worth the extra for the crack tests - a bit of peace of mind!)

Good luck - if you want to know anything just PM me or post again here - I check daily anyway.
 
#20 ·
Thanks again for your replies mate.
I have just changed the thermostat to the 180deg one, no problems. I took it for a drive and temp reading is noticably lower, between the A and L in normal, used to be around the M in Normal. Im happy with that, when I floored it the temp did not rise. I wasn't able to notice the temperature rise issue because that is only on a cold start so I'll wait until tonight or tomorrow morning.

Im really hoping its not the head gasket and that this solves it, I'll monitor closely over the next week or so and live in denial until I notice more coolant going or the pressure remaining as you said... If I have to replace the head gasket I'd probably like to do it myself, although it may take some time... I am a newbie mechanic heh and its probably out of my scope but if I take my time with it hopefully could get it done (and get head checked out) and learn some things in the mean time...

I havn't noticed it idling rough immediately after a start, I'll look for that also on my next cold start.
 
#21 ·
I had a nosey at my mates EFII Fairmont today - without taking the guards off I can't see a specific cooling system bleed point - but the thermostat housing appears to be the highest point. It may well be worth getting a workshop manual for it - especially if you're contemplating doing the head gasket yourself if it turns out to be that.
 
#22 ·
I've got a good manual for the car yep but still will have a hard time with it if i have to do it for sure...

Today (yes it was hot) I drove about 30km and the temp guage went up to about half way, I don't think even in the heat it should do this, should stay at the A in normAl shouldn't it ? I have the cooler thermostat also.
 
#24 ·
Ok, I've done a little more testing, havn't had time to get a block test done because of work though. Coolant is still continuing to leak at fairly quick rate (250mL or so per day my estimation), I put more coolant in and attached a coke bottle to the end of the little hose that leaves the coolant reservoir and usually leads to underneath the car (as to allow overflow to leave). To my suprise I havn't found coolant in the coke bottle just yet (I only set this up this morning), coolant is definitely still going missing and pressure tests have found nothing.

Also something to mention was that this morning at 9am I took off the cap on the coolant reservoir to put more coolant in, there still seems to be a bit of pressure as the coolant came up quickly and all over my hand (cold though yes), is this normal ?? The car had not been running since 6pm yesterday.
 
#25 ·
If there is that sort of pressure in the cooling system after that length of time then there's (compressed) air in the system. Sorry to say but I'd hazard an educated guess the air is from the cylinders ie blown head gasket.....

You'd have to do a cooling system leakdown test to show any pressure loss - pressurise the cooling system & note the pressure & come back in a few hours. The pressure should not drop. If it does then start the motor & see if it doesn't run so flash initially (water in the cylinder). Check the spark plugs - a really clean one with the others normal will mean a problem.
 
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