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Old 31st October 2019, 08:21   #1
TOMPARKER44
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Default MG ZTT CDti - heater hot air problem

Hello all,

I have had my car for 9 years now and it's done 180k. 2 years ago had problems with muck in coolant, coolant loss and excess smoke from exhaust. The heater also didn't blow hot air. After taking it to a garage ended up having the head gasket replaced and new injector O rings. That fixed those problems....apart from the heating, still blowing cold. Had the air-con filled up and all ok there now. Now it's Winter windscreen gets very wet and freezes inside and heater only kicks in when I accelerate over 2400 rpm and it's not that hot even then.

I have read about thermostat, heat exchanger, air in coolant system etc....but before I do anything can anyone guide me to what checks I should do in which order to fix this please? I don't want to waste my time taking the heat exchanger out and cleaning if it's the thermostat etc..
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Old 31st October 2019, 10:18   #2
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Originally Posted by TOMPARKER44 View Post
Hello all,

I have had my car for 9 years now and it's done 180k. 2 years ago had problems with muck in coolant, coolant loss and excess smoke from exhaust. The heater also didn't blow hot air. After taking it to a garage ended up having the head gasket replaced and new injector O rings. That fixed those problems....apart from the heating, still blowing cold. Had the air-con filled up and all ok there now. Now it's Winter windscreen gets very wet and freezes inside and heater only kicks in when I accelerate over 2400 rpm and it's not that hot even then.

I have read about thermostat, heat exchanger, air in coolant system etc....but before I do anything can anyone guide me to what checks I should do in which order to fix this please? I don't want to waste my time taking the heat exchanger out and cleaning if it's the thermostat etc..
First thing I would do is check the heater matrix,,Get the car warm turn the temp up on the ATC and feel pasenger side and driverside vents for hot air.If you find the passenger side cooler than the drivers side it could mean the matrix needs flushing out.As they tend to fill up with silt. You have already said you have had muck in the coolant
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Old 31st October 2019, 10:53   #3
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very interested in this!!!!!!

my cdt just drinks coolant. there is supposed to be a leak somewhere but I cant seem to find it. Every time I fill the bottle up its empty by the next time I look in it. the temp doesn't over heat. The heater / AC sometimes gets warm but normally i just blows cold.
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Old 31st October 2019, 11:26   #4
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very interested in this!!!!!!

my cdt just drinks coolant. there is supposed to be a leak somewhere but I cant seem to find it. Every time I fill the bottle up its empty by the next time I look in it. the temp doesn't over heat. The heater / AC sometimes gets warm but normally i just blows cold.
Check your coolant cap O-rings, also how much coolant are you putting it and to what level.

1

2

You can see that these O-rings are starting to chamfer slightly not completely dome shape.
3

As opposed to these ones.
4

5

The cap also as to be tight ie turn it until its hard to move, if to mush coolant in the tank and the cap is not fully down combined with poor O-rings you will lose coolant through the cap.

PS regarding heat from blower your stat could be opening too soon, most of them on diesels go that way in the end so an inline stat is added.
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Old 31st October 2019, 11:37   #5
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As a diesel, it may well be suffering the widespread problem of the underperforming thermostat. It's very common and has filled reams of forum space over the years. Of course, you won't get any heating if the coolant's not hot enough, so I'd suggest you first check the actual running temperaure. Don't rely on the temperature gauge to tell to anything. The pointer at 'normal' means very little. If it runs below the 'normal' point, you know it's below 75C, which is pretty poor for everything, heating, fuel economy and engine wear. So, run the Trip Screen Diagnostic test while driving normally and tell us the result. You want it near 90C.


HowTo (see section 7): https://www.the75andztclub.co.uk/for...ad.php?t=55585


Diesel owners with the low temperature running issue typically fit the in-line thermostat modification with good results. Choose the stat carefully though using advice on here.


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Old 31st October 2019, 11:42   #6
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Originally Posted by TOMPARKER44 View Post
... windscreen gets very wet and freezes inside ...
It looks as though you have rainwater ingress somewhere or a defective seal allowing damp air in.
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... and heater only kicks in when I accelerate over 2400 rpm and it's not that hot even then.
I'd suspect air in the cooling system Tom. Here's the MG Rover bleeding procedure for the diesel.
This is the easiest thing to try first. You'll need to follow the stages exactly; no missing bits out or starting the engine with the bleed screw removed!

Simon
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Old 31st October 2019, 13:10   #7
Briodyjl01
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Quote:
Originally Posted by Arctic View Post
Check your coolant cap O-rings, also how much coolant are you putting it and to what level.

1

2

You can see that these O-rings are starting to chamfer slightly not completely dome shape.
3

As opposed to these ones.
4

5

The cap also as to be tight ie turn it until its hard to move, if to mush coolant in the tank and the cap is not fully down combined with poor O-rings you will lose coolant through the cap.

PS regarding heat from blower your stat could be opening too soon, most of them on diesels go that way in the end so an inline stat is added.

I actually replaced the 0 rinfs not too long ago as I thought it could be this. the car has done 240,000 miles so I accept little issues. I have been looking at the in line stat fix.
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Old 31st October 2019, 15:42   #8
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thanks all for the help

Number 6 - will give that a go (this evening) and see what happens, although my car never reaches temp (9 o'clock)

T-cut - will try (this evening) and get that to work but don't have a trip computer on my car, would be useful to see engine temp though!

SD1too - will do yours too over the weekend
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Old 31st October 2019, 15:44   #9
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....just started to read your how to T-Cut so ignore the bit about not having a trip computer!
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Old 31st October 2019, 16:55   #10
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... my car never reaches temp (9 o'clock)
Your thermostat is definitely faulty then. That needs sorting out first because your coolant isn't even reaching 75 degrees C!

Simon
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