More noisy cooling fans...?

Charlie bizarrely · 9th January 2017, 19:13

My 2003 daily-use MG ZT 1.8 turbo has for some time (months or more) been making a lot of noise after a run, a fearsome roar that I presume is the fan running at high speed. Typically carries on a few seconds after switching off the engine. I know this topic's been covered numerous times, recently within the "Radiator cooling fan running all of the time" post but I've not absorbed how the expertise on display might explain exactly what's going on with mine.

Comments I've seen imply I ought to have 2 fan speeds cutting in around 104 & 112 deg. C respectively. I'm only aware of one "noisy" speed so today I set the trip-button diagnostics (press x 19, press x 7) to display engine temp, hoping to see when it cut in. With an 11 mile run in 8 degree C outside temperature, after a few miles engine temp display settled around 96C with the heater on & around 104C with heater off. It never read higher that 106 but pulling up at journey's end on tick-over, I could hear the 'roar' which again carried on a few moments after switching off ignition.

Is it likely the high fan speed is cutting in prematurely? This is winter but it surely can't run any more ferociously if running temp should reach the 112C region! Can I easily check if I have a 2-speed fan? I gather later cars don't. Is it controlled by the resistor / relay circuitry referred - if so is this likely to be faulty? 'Cos something is getting far too excited for the time of year.

Many thanks...

SD1too · 9th January 2017, 19:48

From first impressions Charlie it sounds as if your engine is overheating because your fan resistor has failed. Carry out the famous 'demist' test:

Start the engine from cold.
Press the windscreen demist button.
Get out of the car and walk to the radiator grille.
Is the radiator fan running continuously (not cycling on and off)?

Simon

T-Cut · 9th January 2017, 19:54

All 1.8 engines hav a 2-speed fan system. The later versions have resistor control for slow speed. The earlier one has motor brush control for the two speeds.

You need to determine which type is fitted. The easy way is to check for the resistor. This will be located on the fan frame, behind the blades in the 2 o'clock position. You have to look through the grill. There are lots of photos showing the slim aluminium coloured unit.

The next check is for low speed operation. With the cool engine ticking over, press the Demist button. This invokes the aircon system and switches on the fan at slow speed. Go to the front, lift the bonnet and confirm if the fan is running continuously. It should be.

If it runs in short start-stop bursts at high speed, then the slow speed has failed.

The fix will depend on which motor system you have. Hopfully you'll just need the resistor upgrade. If so, the gold version is available from forum traders, from ebay of from outlets like Maplin, RS Components, etc. There are also HowTos on doing the job.

TC - the slow typer.

Charlie bizarrely · 10th January 2017, 14:00

Thanks SD1too & T-Cut.

Brief reply as I wrote a longer carefully-edited one, then somehow got un-logged from the forum & lost it.

Starting from cold, when pressing the demist button the fan comes on & runs steadily, continuously (but rather vigorously / loud). Is this 'normal', or should it be calm & quiet if this is a low speed test?

Looking through the grille mesh, I can't see any resisitor behind the fan blades (2pm or elsewhere) - perhaps mine is brush-controlled...?

Thanks again.

T-Cut · 10th January 2017, 15:27

Quote:

Originally Posted by Charlie bizarrely

Starting from cold, when pressing the demist button the fan comes on runs steadily & continuously (but rather vigorously / loud). Is this 'normal', or should it be calm & quiet if this is a low speed test?

There's nothing calm and quite about these fans, even at 'slow' speed. It appears to be OK.

Quote:

Looking through the grille mesh, I can't see any resisitor behind the fan blades (2pm or elsewhere) - perhaps mine is brush-controlled...?

It's most likely the earlier system then. A few resistors got fitted out of sight, but that's abnormal and rare. From your Demist test, the fan is running normally. The running temperature is too high. It should run around 90C with or without the heater. It sounds like the heater is working better than the radiator. This points to a thermostat issue. Do you know if it has a PRT? Also, is the coolant level correct? Do you have to top it up very often?

TC

Charlie bizarrely · 10th January 2017, 16:08

Cheers T-cut.
"There's nothing calm and quite about these fans" - lol!

Re. "It should run around 90C with or without the heater"; last night's run with the above temp figures was up twisty lanes & B-roads.

On the run to work this morning (5 degrees C outside) I set the temp diagnostic again & left the heater off the whole 11 mile journey. I took the motorway for about 8 miles, at 70mph it was steady at 92-93 degrees C. The last couple of miles around town (Watford) it rose slightly & settled around 102-103C. I never heard the fan come on at all, but restarted the engine after stopping a few minutes & it came on straight away. (Possibly I may have selected demist, can't remember).

Not sure about the PRT - plumbing has the plastic T-piece just behind the top centre of the rad, if that's a clue? Or how best can I check/confirm?

Coolant is just visible when cap is removed & rarely needs topping but I'm watching if like a hawk.

T-Cut · 10th January 2017, 16:51

Quote:

Originally Posted by Charlie bizarrely

The last couple of miles around town (Watford) it rose slightly & settled around 102-103C.

It's cerainly on the warm side.

Quote:

I never heard the fan come on at all

As you've noted, it will trip on at about 104C.

Quote:

but restarted the engine after stopping a few minutes & it came on straight away.

That's heat soak. This happens quite easily if it's running warm anyway.

Quote:

Not sure about the PRT - plumbing has the plastic T-piece just behind the top centre of the rad

Yes, it has a PRT.

Is this warm running a new thing or is there a history you're aware of?

TC

Charlie bizarrely · 27th January 2017, 21:18

"Is this warm running a new thing or is there a history you're aware of?"

It's been behaving like this as long as I can recall, for years I think. But late November it had a ghastly overheating episode during high speed motorway driving which led to much replacement of parts including PRT thermostat, waterpump etc. This made me somewhat nervous (hence this post) concerning it's 'normal behaviour' which is not discernably any different, following fitting of the new parts, coolant flush etc.

It suffers has the 'cold passenger footwell syndrome' which I gather means the heater matrix needs flushing out, this fault has persisted quite some time too - could that be contributing to a high running temperature?

Apologies for delayed responses, I only have occasional access to the forum / internet.

T-Cut · 27th January 2017, 23:10

There's a problem dubbed double thermostat jeopardy (Google search term DTJ), that results when a 1.8/1.8T with a PRT is fitted with a standard thermostat in the upper housing. This happens following HGF, where a garage finds the usual stat housing 'empty' and fit a new one. These engines suffer rapid and consistent overheating as a result. Of course DTJ isn't the only cause of overheating, but it's surprisingly common and not well known. It's something to check out if you believe the engine has suffered HGF before you got it.

DTJ Google search:https://cse.google.co.uk/cse?hl=en&c...ab=0&gsc.q=DTJ

TC

9th January 2017, 19:13	#1
Charlie bizarrely Regular poster MG ZT Join Date: Nov 2012 Location: Leverstock Green Posts: 64 Thanks: 6 Thanked 4 Times in 4 Posts	More noisy cooling fans...? My 2003 daily-use MG ZT 1.8 turbo has for some time (months or more) been making a lot of noise after a run, a fearsome roar that I presume is the fan running at high speed. Typically carries on a few seconds after switching off the engine. I know this topic's been covered numerous times, recently within the "Radiator cooling fan running all of the time" post but I've not absorbed how the expertise on display might explain exactly what's going on with mine. Comments I've seen imply I ought to have 2 fan speeds cutting in around 104 & 112 deg. C respectively. I'm only aware of one "noisy" speed so today I set the trip-button diagnostics (press x 19, press x 7) to display engine temp, hoping to see when it cut in. With an 11 mile run in 8 degree C outside temperature, after a few miles engine temp display settled around 96C with the heater on & around 104C with heater off. It never read higher that 106 but pulling up at journey's end on tick-over, I could hear the 'roar' which again carried on a few moments after switching off ignition. Is it likely the high fan speed is cutting in prematurely? This is winter but it surely can't run any more ferociously if running temp should reach the 112C region! Can I easily check if I have a 2-speed fan? I gather later cars don't. Is it controlled by the resistor / relay circuitry referred - if so is this likely to be faulty? 'Cos something is getting far too excited for the time of year. Many thanks... __________________ [SIGPIC][/SIGPIC] Cheers, C.B.

9th January 2017, 19:48	#2
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,637 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	From first impressions Charlie it sounds as if your engine is overheating because your fan resistor has failed. Carry out the famous 'demist' test: Start the engine from cold. Press the windscreen demist button. Get out of the car and walk to the radiator grille. Is the radiator fan running continuously (not cycling on and off)? Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

10th January 2017, 14:00	#4
Charlie bizarrely Regular poster MG ZT Join Date: Nov 2012 Location: Leverstock Green Posts: 64 Thanks: 6 Thanked 4 Times in 4 Posts	More noisy cooling fans...? Thanks SD1too & T-Cut. Brief reply as I wrote a longer carefully-edited one, then somehow got un-logged from the forum & lost it. Starting from cold, when pressing the demist button the fan comes on & runs steadily, continuously (but rather vigorously / loud). Is this 'normal', or should it be calm & quiet if this is a low speed test? Looking through the grille mesh, I can't see any resisitor behind the fan blades (2pm or elsewhere) - perhaps mine is brush-controlled...? Thanks again. __________________ [SIGPIC][/SIGPIC] Cheers, C.B.

10th January 2017, 16:08	#6
Charlie bizarrely Regular poster MG ZT Join Date: Nov 2012 Location: Leverstock Green Posts: 64 Thanks: 6 Thanked 4 Times in 4 Posts	More noisy cooling fans...? Cheers T-cut. "There's nothing calm and quite about these fans" - lol! Re. "It should run around 90C with or without the heater"; last night's run with the above temp figures was up twisty lanes & B-roads. On the run to work this morning (5 degrees C outside) I set the temp diagnostic again & left the heater off the whole 11 mile journey. I took the motorway for about 8 miles, at 70mph it was steady at 92-93 degrees C. The last couple of miles around town (Watford) it rose slightly & settled around 102-103C. I never heard the fan come on at all, but restarted the engine after stopping a few minutes & it came on straight away. (Possibly I may have selected demist, can't remember). Not sure about the PRT - plumbing has the plastic T-piece just behind the top centre of the rad, if that's a clue? Or how best can I check/confirm? Coolant is just visible when cap is removed & rarely needs topping but I'm watching if like a hawk. __________________ [SIGPIC][/SIGPIC] Cheers, C.B.

27th January 2017, 21:18	#8
Charlie bizarrely Regular poster MG ZT Join Date: Nov 2012 Location: Leverstock Green Posts: 64 Thanks: 6 Thanked 4 Times in 4 Posts	More noisy cooling fans... "Is this warm running a new thing or is there a history you're aware of?" It's been behaving like this as long as I can recall, for years I think. But late November it had a ghastly overheating episode during high speed motorway driving which led to much replacement of parts including PRT thermostat, waterpump etc. This made me somewhat nervous (hence this post) concerning it's 'normal behaviour' which is not discernably any different, following fitting of the new parts, coolant flush etc. It suffers has the 'cold passenger footwell syndrome' which I gather means the heater matrix needs flushing out, this fault has persisted quite some time too - could that be contributing to a high running temperature? Apologies for delayed responses, I only have occasional access to the forum / internet. __________________ [SIGPIC][/SIGPIC] Cheers, C.B.

9th January 2017, 19:54	#3
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,754 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	All 1.8 engines hav a 2-speed fan system. The later versions have resistor control for slow speed. The earlier one has motor brush control for the two speeds. You need to determine which type is fitted. The easy way is to check for the resistor. This will be located on the fan frame, behind the blades in the 2 o'clock position. You have to look through the grill. There are lots of photos showing the slim aluminium coloured unit. The next check is for low speed operation. With the cool engine ticking over, press the Demist button. This invokes the aircon system and switches on the fan at slow speed. Go to the front, lift the bonnet and confirm if the fan is running continuously. It should be. If it runs in short start-stop bursts at high speed, then the slow speed has failed. The fix will depend on which motor system you have. Hopfully you'll just need the resistor upgrade. If so, the gold version is available from forum traders, from ebay of from outlets like Maplin, RS Components, etc. There are also HowTos on doing the job. TC - the slow typer.

27th January 2017, 23:10	#9
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,754 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	There's a problem dubbed double thermostat jeopardy (Google search term DTJ), that results when a 1.8/1.8T with a PRT is fitted with a standard thermostat in the upper housing. This happens following HGF, where a garage finds the usual stat housing 'empty' and fit a new one. These engines suffer rapid and consistent overheating as a result. Of course DTJ isn't the only cause of overheating, but it's surprisingly common and not well known. It's something to check out if you believe the engine has suffered HGF before you got it. DTJ Google search:https://cse.google.co.uk/cse?hl=en&c...ab=0&gsc.q=DTJ TC Last edited by T-Cut; 27th January 2017 at 23:12..