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Old 1st November 2019, 00:12   #11
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Originally Posted by TOMPARKER44 View Post
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!
The trip mileage reset button is what you use. All 75/ZTs have one and all can run in Diagnostic Mode. Read the HowTo and you can't go wrong.

EDIT: Ah, I see you've twigged it.


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Old 1st November 2019, 01:42   #12
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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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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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Old 1st November 2019, 10:04   #13
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... my cdt just drinks coolant. there is supposed to be a leak somewhere but I cant seem to find it.
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... it is reading high 80s to high 90s but fluctuating up and down a lot ... But the heater is still freezing ... about 2500 RPM it starts to get warm then drops cold again when you slow down
Josh; the most likely reason for this is that your cooling system isn't pressurising probably due to an ineffective seal between two components or, for example, a tiny defect in the radiator. These can be very hard to find and won't necessarily result in a stream of visible coolant.

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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Old 1st November 2019, 10:06   #14
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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 oil level!!! Is it going up?
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Old 1st November 2019, 11:15   #15
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Josh; the most likely reason for this is that your cooling system isn't pressurising probably due to an ineffective seal between two components or, for example, a tiny defect in the radiator. These can be very hard to find and won't necessarily result in a stream of visible coolant.

The other possibility is an air lock particularly if work has been carried out and the proper refilling/bleeding procedure not followed.

Simon

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.
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Old 1st November 2019, 11:16   #16
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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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Old 1st November 2019, 12:10   #17
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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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Old 1st November 2019, 12:21   #18
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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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