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Engine cooling system question

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Engine cooling system question
11 April 2009, 6:17 PM
JP147
Joined 29 Dec 2007
31 posts

This question is about a 1.8 petrol Ford Focus.

I would like to know from any mechanics about what the possible causes may be for the following symptoms :

1. When starting the car from cold in the morning and during the first journey the temperature guage needle after rising slightly then drops slightly (I sometimes actually see it happen) when for example stopped at traffic lights.

2. Secondly, after switching off the engine and then I turn the ignition such that the engine is off but the temperature guage is functional, the needle usually has dropped quite a bit from the mid position even though I have only just switched the engine off (so it is still hot).

3. Lastly, I feel the needle is never exactly mid way between cold and hot but slightly nearer the cold end. Would this suggest a head gasket problem ?

Would any of these symptoms suggest a problem with the coolant pump, radiator or any related component ?

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Engine cooling system question
11 April 2009, 6:57 PM
bas saph
Joined 20 Dec 2007
2035 posts

not a machanic. but I would put it down to an eletrical fault. cars oftern run with temp gauge just above cold as normal run temp will vary a lot depending of circumstances.


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Engine cooling system question
11 April 2009, 7:28 PM
-  Edited by tommytwotanks 11 April 2009, 7:31 PM
tommytwotanks
Joined 25 Aug 2006
1064 posts

if i was going to change anything it would be the temperature sensor/sender,
if your head gasket was suspect you would have oil in the water/expansion tank, mayonnaise in the rocker cover, and/or the oil in the sump would be milky and gaining height on the dipstick, due to using the water from the expansion tank, if your using water the heater may not work, and the temperature reading may go up and down, due to air locks in the system, you may also have steam or smoke coming from the exhaust, you may not have all of these symptoms, so there is some good news, lol
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Engine cooling system question
11 April 2009, 7:35 PM
Iceni
Joined 9 Apr 2007
146 posts

The cooling system is controlled by a thermostat at the cooling outlet from the engine block.

When the temperature of the coolant at this point is high enough the thermostat opens slightly; coolant then starts to flow.

The hot coolant flowing through the thermostat opens further letting more through.
Simultaneously cold coolant from the radiator flows in the bottom of the engine block.

As it flows through the coolant channels it gets warmed and as a result cools the engine.

When the recently entered slightly warm coolant reaches the thermostat it is not sufficiently hot to keep the thermostat open; so it closes.

So now we have a warm engine surrounded by cold-ish coolant. Consequently the whole engine engine temperature drops (as you see on the gauge).

The whole cycle now repeats, but each time it repeats the engine is slightly warmer until finally it is hot enough to heat the entering coolant to a temperature that when it reaches the thermostat is hot enough to keep it open.

This is why efficiency drops in the winter. The water entering the engine is that much colder it takes the engine much longer to get to its operating temperature.

Ideally there should be thermostatically controlled louvres on the radiator to control air flow and maintain a steady temperature in the radiator as well.

I hope that explains the gauge dropping issue.

Discussion Archived

Engine cooling system question
15 April 2009, 9:10 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

Blimey you know your stuff, do you know anything about lamda sensors?
Ford Escort 1.8si, 97
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Engine cooling system question
16 April 2009, 8:02 PM
carlos
Joined 2 Jun 2007
142 posts

hi what do you want to know and why ie has yours failed emmissions or do you just want to know how they work? regards carlos
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Engine cooling system question
16 April 2009, 8:38 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

Yeah my car just went in for mot and it failed on the lamda test, exhaust emissions, will buying a new sensor cure the problem? some people say it won't make any difference
Discussion Archived

Engine cooling system question
16 April 2009, 9:20 PM
carlos
Joined 2 Jun 2007
142 posts

this really depends on what the readings were fords do seem to suffer with emmissions however unless the co readings were exceptionly high its unlikely to be probe really need to know all readings to hazard a guess
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Engine cooling system question
16 April 2009, 9:47 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

Fast idle test
rpm 2500-3000, CO max limit 0.200, actual value 0.004

HC max limit 200, actual value 16

lambda min limit-0.970 max limit-1.030, actual value 1.002 but the mechanic said he had to rev the b$$$$$$s out of it to get it to that reading.

Does this help, i got it off the mot

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Engine cooling system question
16 April 2009, 10:01 PM
carlos
Joined 2 Jun 2007
142 posts

no this doesnt help those readings should have passed, i can only think its the natural idle that failed look on your test sheet and see which bit says failed please
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Engine cooling system question
16 April 2009, 10:10 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

i told you when it passed mot, what a doughnut lol.
anyway the failure is as follows, CO fine but the lambda test failed with 3 not oks, lambda reading 1.558, rpm 1/min 2500-3000 measured 0
what u reckon?
Discussion Archived

Engine cooling system question
16 April 2009, 10:25 PM
carlos
Joined 2 Jun 2007
142 posts

its a little bit difficult to decipher but if your saying all other readings apart from lamda being high ie 1.558 at idle then id say youve either got an air leak or a boy racer back box fitted
Discussion Archived

Engine cooling system question
16 April 2009, 10:44 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

u mean leak in the exhaust? or the inlet manifold?
Discussion Archived

Engine cooling system question
16 April 2009, 10:47 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

no boy racer back box im 29
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Engine cooling system question
16 April 2009, 10:48 PM
bas saph
Joined 20 Dec 2007
2035 posts

lol im 32 and should see my cars. pmsl


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Engine cooling system question
16 April 2009, 10:54 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

I only have one car, so bk to the sensor then?
Mechanic said change it? what you reckon?
Are they pricey?
I rang fords other day, asked for a price on an o/s anti-roll bar drop link, £42 PLUS VAT,
I said to the bloke, behave yourself, i aint no mug, i'll get it from halfords pmsl
Discussion Archived

Engine cooling system question
17 April 2009, 7:41 AM
carlos
Joined 2 Jun 2007
142 posts

hya ,1.558 seems high even for an air leak.you can get after market probe from motor factors £45 but you have to solder them think main dealers about £90 its to difficult to say this will cure fault as the readings you give dont really make sense, if you had air leak inlet side you wud cetainley have idling issues on exhaust side you should be able to hear it ie,blowing noise from exhaust.
it may be worth taking it 4 a bloody good thrasing and taking back to garage and ask em if they mind checking it again, depends how helpful your garage wants to be hope this helps a little either way u will need to spend some money cars hey great wen there ok pain in the arse wen they go wrong off to work now will look in later bye all

3

Discussion Archived

Engine cooling system question
17 April 2009, 10:10 AM
bas saph
Joined 20 Dec 2007
2035 posts

just a suggestion could it be the air filter condition ?


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Engine cooling system question
17 April 2009, 9:04 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

Ok, well this seems to be a problem.
It failed test, so i was told by the mechanic to boot it, i drove 100mph for 10miles, tryin to avoid the blues and 2s lol joke, anyway, so i done that went bk for test and it passed but that had to rev it up really high to get lamda reading pass.

I do have a problem with idling go up the road and sometimes it nearly cuts out, only now and again, most of the time it idles 750rpm, where would the air leak be?
On the inlet manifold?
Lovely fords innit, the dagenham dustbin lol

You say the after market probe, you have solder it?
it looks to me just like a nut, bit like oil switch

Discussion Archived

Engine cooling system question
17 April 2009, 9:08 PM
FACOM MOTORS
Joined 11 Feb 2009
55 posts

no not the air filter lol
In saying that anyone want a K&N Filter for a ford escort 1.8si, 97?
Discussion Archived

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