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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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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https://i.imgur.com/FNwNhjBl.jpg1 https://i.imgur.com/pvCdIGCl.jpg2 You can see that these O-rings are starting to chamfer slightly not completely dome shape. https://i.imgur.com/zRe2Bpdl.jpg3 As opposed to these ones. https://i.imgur.com/CAuuqnUl.jpg4 https://i.imgur.com/tRUZWnOl.jpg5 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. |
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. TC |
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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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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. |
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 |
....just started to read your how to T-Cut so ignore the bit about not having a trip computer!
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Simon |
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EDIT: Ah, I see you've twigged it. TC |
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I have done the coolant temp check and it is reading high 80s to high 90s but fluctuating up and down a lot between them number. But the heater is still freezing and like the original poster said about 2500 RPM it starts to get warm then drops cold again when you slow down |
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The other possibility is an air lock particularly if work has been carried out and the proper refilling/bleeding procedure not followed. Simon |
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When I bleed it I do it the same way I do my metros, open the bleed screw next to the battery and put a funnel n the coolant bottle and fill that with coolant to force the air out. I know that works on them. |
someone said earlier on in the post about 2500 rpm and it gets warm. this is what mines doing as well.
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You have an airlock Josh, I would remove the hoses that go to the matrix and back flush them, then refill and bleed correctly and see what happens.
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And here is the correct method of refilling/bleeding a 75/ZT diesel Josh.
To increase your chances of success at the first attempt, I would follow MG Rover's recommendation that the system is first fully drained (after which you can back-flush the heater matrix as Trikey suggests) including the cylinder block drain plug. I don't have a diesel, I have a petrol 75, but by following the MGR procedure for my engine exactly, I have never had an air lock, overheating or poor heater performance. Let us know how you get on. :} Simon |
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