75ZT Community

I have had the misfortune recently to find that my thermostat is leaking into the V of the engine.

I have recently found a leak from the thermostat on my MG ZT 190 V6.

I check the car once a week for all hose leaks etc, all fluids levels be it oil or water, so as per usual on 9th March Sunday I did all the relative checks and everything was fine.

In the mean time I took delivery of a new coolant cap which I had purchased from a vender to see it's quality for the price that is another story, anyways on the 12th March coolant cap arrived the very next day 13th March i thought i will change the cap and see how it looks and works with regards to the original.

Once i took the original cap of the header tank i could see that the level of coolant had drop from the max mark to a fraction below the minimum mark only checked three days ago all was well and have only driven the car 30 miles in those three days, so i take of the engine cover look into the V and there is the problem looking me right in the face coolant loss from the thermostat albeit only a little but never the less a leak.
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As you can see this is very fresh coolant as it is as red as blood, now my MG ZT 190 was fitted with a new thermostat on the 21/01/12 and as only covered approx 3,700 miles since it was fitted. Fig 2
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I was surprised to find this in the mean time i have not driven the car and ordered a new thermostat which arrived 18/3/14. Fig 3
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Well I finally got round to finding enough time to change the thermostat Saturday 29th March, first I decide I will take of the engine cover and check to see if the leak as got any worse, the answer was no Fig 4/5/6 below.
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I will post how I removed the thermostat and refitted over the next few days keep looking in Arctic

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On the 13th March I discovered I had a leak from the thermostat on my MG ZT 190 I noticed this as the coolant in the header tank was low, so I checked in the V of the engine and sure enough I could see the red coolant not much but enough to have to remove and replace the thermostat.

Below is how I removed and fitted the thermostat I hope this helps some other members if they have to do the same job, remover the under tray before starting the task,the thermostat I removed had only been fitted for 2 years with limited mileage of about 3.700miles.

First remove the engine cover two 8mm bolts Fig 1
1

Remove the cover and put it in a safe place with the bolts Fig 2
2

Using a torch and shinning it through the gap in the manifold I can see the leak Fig 3
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The next step is to remove the air filter box from the engine bay, loosen the hose clip on the throttle body inlet hose Fig 4

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Pull off the small air induct hose pipe Fig 5/6
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6

Next you can pull up the air box it may be stiff as it sits in the holes and is held in by the lugs under the box Fig 7/8
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8

You now need to release the Shannon tube from the air box Fig 9/10
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10

Air box removed put it safe with the engine cover in the boot of the car out of arms way Fig 11
11

You may see a little oil in the air induct hose this is normal and can be cleaned out before re-fitting Fig 12
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There may also be a little oil in the throttle body again do not worry Fig 13
13

You can now see the three hoses that are connected to the thermostat and the bleed screw Fig 14
14

Later you will also need to remove the bottom hose that is the reason for removing the under tray before starting the task. Fig 15
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The next parts to remove are the breather hoses, the first one is the one connected to the vis motor & throttle body and the front Fig 16/17/18/19
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These hoses are removed by depressing the red locking collars Fig 20/21
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You will have to use a screw driver to depress the locking collar connected to the vis motor Fig 22/23
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The last locking collar on the top breather pipe is connected to the top of the throttle body and is black an again a screwdriver may be used Fig 24/25
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You can now pull back the engine bracket and feed the hose past it Fig 26/27
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With the hose removed again put it in the boot for safety Fig 28
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You can now remove the second breather hose Fig 29
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Start at the front cylinder head again depress the collar Fig 30/31
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31

Them move to the collar on the manifold Fig 32/33
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33

The last part of this hose to be removed is the T piece, this is held in by a white collar Fig 34
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This white collar needs to be pressed in at both ends and twisted to release the hose Fig 35
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Once remove inspect it and make sure it is in good order no cracks or splits and put it in the boot Fig 36
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Next step disconnect the vacuum hose from the idle control valve Fig 37
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Place this hose to one side for now Fig 38
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You can now unplug wiring plug from the throttle body Fig 39/40
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unclip the next plug underneath by depressing the metal spring clip Fig 41/42/43
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With the two wiring plugs removed set them out of the way Fig 44
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Next we turn our attention to the throttle cable Fig 45
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lift the throttle lever and remove the cable 46/47
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We now need to remove the throttle body it's self which is secured to the manifold by four torx 30mm bolts two above and two below Fig 48/49/50
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You will need to use a long reach socket and ratchet with 30mm torx start with left top bolt Fig 51
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Next bottom left Fig 52
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Bottom right Fig 53
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Last top right Fig 54
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Once removed inspect and clean up with a bit of WD 40 and in the boot with it Fig 55
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You can now put a container under the bottom radiator hose and remove it to let out the coolant Fig 56/57
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This hose with the bleed screw in it will be removed once the coolant as be drained off Fig 58
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To Be Continued

Continued from part 1.
I then tied back the breather hose so it would not be in my way later Fig 59
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The next step is to remove part of the thin header tank hose again for more access later Fig 60
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To help get to the hose above better remove the lead of spark plug 61
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With the lead removed you can use some grips to open the hose clip and set it back Fig 62
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You can now pull out the T junction as here fig 63

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We now need to remove the right hand side of the header tank hose from the T joint Fig 64
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As before release the hose clip with some long nose grips or mole grips and remove the hose Fig 65
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The hose can now be moved to the front of the engine out of the way Fig 66
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The other part of the hose can be tied back with the breather pipe with the white collar from before Fig 67
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Now that the thin header tank hose is out of the way you will see there is some wiring also that will need to be lifted later, but as you can see another breather hose is lying over the top of it this will also have to be removed Fig 68
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To remove this last breather pipe again as before press the red collar and it will release Fig 69/70
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Breather pipe pulled out Fig 71
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Removed from the engine put it safe in the boot with the others Fig 72
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Now with most of the items out of the way we can see the thermostat and the hoses connected to it Fig 73
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You can now check the header tank it should be empty Fig 74
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Also check at the bottom hose & rad to see if the coolant as stopped coming out Fig 75
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We are now ready to remove the large hose with the bleed screw attached to it again use long nose grip if you have some if not mole grips will do or pliers Fig 76
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Once removed from the car put it safe Fig 77
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With the first hose removed we can then turn our attention to the other two Fig 78/79
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Now release the clip from the next large hose and pull it backward Fig 80/81/82
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This hose is connected to the top of the radiator Fig 83
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With the clip released you can now pull off the hose expect a little more coolant to drain out Fig 84
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You can now tie this hose out of the way Fig 85
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Before you carry on mop or soak up the split coolant, this can be avoided if you remove the block tap Fig86/87
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We are now ready to remove the last hose from the middle the smaller of the hoses Fig 88/89
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Now that the middle hose as been removed and tied back to the other one, we can turn our attention to removing the 10mm bolt which holds the thermostat in place to the engine block, you will need a thin long reach socket with a knuckle on the end to do this through alloy manifold Fig 90
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Pass the socket through the gap in the manifold as here Fig 91
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Once you have the socket through make sure it is seated on the bolts head properly Fig 92
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Get a good grip and turn the ratchet socket slowly to break the joint on the bolts and it will then release quite easy Fig 93/94
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Once you have the bolt to the end of its thread and still sitting in the elbow joint you will need a telescopic magnet to remove it if not you will be fishing for it later in the V of the engine Fig 95/96/97
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You are now ready to prise out the thermostat housing first try twisting and lifting the elbow bend,the thermostat housing's bolt fixing sits underneath that of the curved pipe, making removal difficult if no joy prise the housing up it's self as here Fig 98
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You will now get some more coolant flow into the V of the engine this can be cleaned up later when all the hosing as been removed and before re-fitting the new housing.
If you are still finding it difficult to remove the housing use the long nosed grips to help as here Fig 99
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remove if you are going to re-use the housing maybe because only the seals have given way then set to one side safe Fig 100
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With the main thermostat housing body remove it will leave the straight piece and the elbow bend in place you can now remove these Fig 101/102
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Those should remove easy now you can clean up inside the V of the engine Fig 103/104
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I also hoovered some coolant out of the openings which the thermostat fits into so it did not over flow when replacing later.Fig 105
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Part three to be continued

Part Three refitting the new thermostat.

With all the thermostat parts in front of you the straight piece, housing, and the bend start by fitting the straight piece into the housing.
Straight piece with Fig 106
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The bend Fig 107
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The thermostat housing with the straight piece fitted into it, this you need to do first before you offer and fit the housing and straight piece back into the engine Fig 108
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Now you have the housing and straight piece together feed them into the V of the engine you can and should smear the ends of the straight piece and the hosing with a lubricant Vaseline etc, make sure you push home the straight pipe and then push the thermostat housing down and in Fig 109
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Double check the straight piece by looking through the manifold holes into the V with a touch as here Fig 110
[IMG]http://i57.tinypic.com/m8chfr.jpg[/IMG110

And also at the housing end as here Fig 111
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Next check the housing it's self is pushed home and seated right, this housing as lugs and only allows the housing to be pushed home as much as it should be Fig 112
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The next step is to fit the bend again making sure the end is lubricated to help it being pushed home with ease Fig 113
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Look through the holes in the manifold again with a torch and make sure you have lined up the adjoining holes in the housing and the bend then offer the bolt to it carefully through the hole in the manifold using the socket and ratchet you remove it with Fig 114
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After fitting the bolt which holds the bend and housing in place double check the straight piece is still in place Fig 115
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Now you are satisfied that the thermostat is fitted correct you can start adding the hoses to the housing pipe work, do the small middle one first Fig 116/117
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Next fit the large one which fits on to the bend Fig 118/119
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You can now fit the hose with the bleed screw in it to the main thermostat housing Fig 120
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And fit the hose also to the bottom of the radiator Fig 121
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With all hose fitted and jubilee clips tightened up make sure the bleed screw is hand tight as you will need to undo this at a later date when bleeding the system. Fig 122
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Fit all the wiring and throttle body with breather pipes back into place Fig 123
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Making sure you fit the throttle cable Fig 124
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If you are working on your own as I was you need to find something to raise the header tank up as far as it will go to refill it slowly, as you can see here I used a short plank of wood Fig 125
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I rested the locating pegs on to the rad housing as here Fig 126/127
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I filled the header tank slowly at the same time I undid the bleed screw and carried on filling until the water came out of the bleed screw then I screwed in back in making sure the coolant never dropped below the minimum level when filling, thus trying my best to avoid an air lock Fig 128
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Once happy i ran the engine with the header tank still raised and kept my eye on the coolant once I saw is rising I added the coolant cap and let the car get up to temperature 91 turned the engine off and let it cool a bit, at this time I again checked in the V to see all was ok and not leaking Fig 129
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I then checked the level in the header tank all seemed ok ran the engine again this time up to 101 and waited for the fan to kick in and bring the temp down to 95 I did this a few times and turned the engine off, I cleaned up all my tools and put them away, I went and ate my tea by the time I had finished an hour had passed and I again checked into the V for leaks etc it was bone dry Fig 130/131
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Also checked at the housing connections Fig 132
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The next morning I again checked the coolant in the header tank and it was spot on with the max mark Fig 133
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I checked again a week later for any leaks etc, nearly 12 months and i will check again and report back Arctic
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