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Old 03-04-2008, 09:07   #1
howard-moore
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2.5 V6 - How to bleed the coolant system

Hi,

This is a question rather than a walkthrough I'm afraid. I have read lots of posts about water gurgling on revving etc., and whilst the heater matrix may be something to do with it, most seem to recommend getting the air out of the system too.

What I would like to know is, for the complete novice, how to bleed the air out of the coolant system. I can't believe that the only way is to run the car with the filler cap off?

I know it's a big ask, but could someone perhaps put a photo of the engine bay of a V6 and point out what valves do what, and what we should do to bleed the system?

Many thanks in advance.
Neil
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Old 03-04-2008, 09:29   #2
courier118
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The only way to rid the coolant system of any air is to have to system vacuum filled.........you really should not refill the coolant system any other way.Do a search on vacuum refill mate
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Old 03-04-2008, 09:45   #3
howard-moore
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I've searched for 'VACUUM REFILL', but I can't seem to find anywhere that describes actually how to do it - only that it has to be done.

Can anyone tell me where there is a 'how to' on how to vacuum fill (or put one here?
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Old 03-04-2008, 11:09   #4
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The kit you require can be bought but is quite expensive.......i think sykes pickivant do one.........go to any reputable garage but preferably an ex MG dealer,they will have the kit to do it for you.......and alot less expensive than going out and buying the kit which if i remember rightly was about 250,maybe be a little bit less than that now
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Old 03-04-2008, 14:14   #5
eumjmorris
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Cooling System filling on 1.8/1.8T.

Guys, can you please confirm, is such a vacuum-fill palaver required on the 1.8 4-cylinder engines too, in the R75/ZT installation. (I've never needed any special procedures on 400/45s, petrol or diesel, not my R75T diesel). Rgds, M.
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Old 03-04-2008, 15:08   #6
1955diesel
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No, it's not "required" on any of the models, but it can make life a lot easier on some.

Any small quantities of air left trapped in the system following manual filling are expelled once the engine is run up to full temperature and the thermostat has been open for a while. The system then needs to cool down before being topped up.

Obviously, if you don't fill and bleed properly, or one of the vents is blocked, you can run into trouble with air locks and lack of circulation leading to boiling.

Garages like to vacuum fill because it takes all the uncertainty out of the procedure.
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Old 03-04-2008, 15:11   #7
howard-moore
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I notice that on the left of the engine (KV6 2.5) there are two metal pipes with valves on them. One valve has 'H' on it, the other has 'L'.

Does anyone know what these are for, and are they anything to do with bleeding the system?
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Old 03-04-2008, 15:14   #8
1955diesel
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High and Low pressure air con pipes? Just follow them and see where they go.
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Old 03-04-2008, 15:28   #9
howard-moore
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That makes sense - but I did note that they got pretty hot, so presumed that they might be part of the heating system. I also touched the 'H' valve a tiny bit to see what happened and high-pressure hiss came out (which I hoped was air trapped in the coolant system). I will however, lay off doing this any more unless someone tells me that they are not air-con pipes!!

I don't suppose anyone has a diagram or a photo of a KV6 engine? It would be a really useful resource to have up on the Forum.
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Old 03-04-2008, 15:47   #10
zedler
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as long as your topping up and there is a steady stream of coolant coming out of the bleed valve then i dont se ethe reason to use vacum filling, i did it on mine and it seems fine,easy to do aswell
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Old 03-04-2008, 15:54   #11
howard-moore
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Quote:
Originally Posted by zedler View Post
as long as your topping up and there is a steady stream of coolant coming out of the bleed valve then i dont se ethe reason to use vacum filling, i did it on mine and it seems fine,easy to do aswell

That's great, thanks. What I would really like to know is where I can find the bleed valve. Hope you can help!

Thanks,
Neil
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Old 03-04-2008, 15:59   #12
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i'll be honest with you mate im not too clued up on the v6 but if you follow your coolant pipe on the metal peice there should be a hexagonal screw thats about the best i can say ,thats what it was on the kseries 1.4 anyway, maybe pm a member with a v6 with alot of reps, they will help you,try empsburna or ashy
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Old 03-04-2008, 16:18   #13
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The 1.8 engines contain barely over 6 litres of coolant. The V6s have 7.5 and the diesel over 8 litres. The 1.8's capacity doesn't leave any margin for air bubbles. The engines are already vulnerable to overheating due in part to this small volume. Air bubbles left in the heater matrix for example will soon make themselves known. If you don't use vacuum refilling, always check the air bleed valve when filling up, then check it again after a short run. Check the level every day for a few days to be absolutely sure it's free of air.

TC
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Old 03-04-2008, 16:22   #14
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Quote:
Originally Posted by howard-moore View Post
- - - but I did note that they got pretty hot, so presumed that they might be part of the heating system. I also touched the 'H' valve a tiny bit to see what happened and high-pressure hiss came out (which I hoped was air trapped in the coolant system). I will however, lay off doing this any more unless someone tells me that they are not air-con pipes!!
The 'H' and 'L' valves are on the refrigerant plumbing for the air conditioning. Don't touch these valves at any time or you'll lose some gas. The refrigerant does get hot due to the way it works. Noticed how warm a fridge gets at the rear? Same thing.

TC
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Old 03-04-2008, 16:23   #15
howard-moore
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Quote:
Originally Posted by T-Cut View Post
The 1.8 engines contain barely over 6 litres of coolant. The V6s have 7.5 and the diesel over 8 litres. The 1.8's capacity doesn't leave any margin for air bubbles. The engines are already vulnerable to overheating due in part to this small volume. Air bubbles left in the heater matrix for example will soon make themselves known. If you don't use vacuum refilling, always check the air bleed valve when filling up, then check it again after a short run. Check the level every day for a few days to be absolutely sure it's free of air.

TC
I hear so much about this fabled 'Air bleed valve' but I have yet to find anyone who can tell me definitively where it is. Do you?

Ta, Neil.
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Old 03-04-2008, 16:44   #16
1955diesel
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The 4 cylinder engines generally have two (MGF has 3). One is in the heater feed pipe before it goes through the bulkhead. The other in in the metal coolant rail that runs over the top of the flywheel housing.

They look like small screws located in the top surfaces of the pipes.

I'm not very familiar with the V6 installation in cars (spent years playing with them on test beds ) so I cant tell you where to look for yours. However, there are not too many feet of coolant pipe under the bonnet so it should not be too difficult to track them down.
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Old 03-04-2008, 16:50   #17
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One is on the return pipe after the oil cooler on the KV6 (don't know of another)

Shroon
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Old 03-04-2008, 17:21   #18
Isis
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It is all well documented in the Haynes manual and at about 20 is quite a bit cheaper than the vacuum kit. Just telling you where the bleed valve is wouldn't be helpful, the procedure isn't as simple as opening a bleed valve and pouring coolant in.

The "other things" you were playing with are for the air-con. I really would recommend getting the Haynes manual, it may not be completely accurate or even completely thorough, but it could save you some money big time or keep you safe in the event of some tinkering going t1t5 up.
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Old 03-04-2008, 17:41   #19
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Agreed, the manual method for the v6, as described in Haynes works just fine, and is sooooooooo straightforward.

I did a thermostat change on my 190 last week and refilled using Haynes method.
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Old 03-04-2008, 18:20   #20
1955diesel
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Quote:
Originally Posted by ZTalker View Post
Agreed, the manual method for the v6, as described in Haynes works just fine, and is sooooooooo straightforward.

I did a thermostat change on my 190 last week and refilled using Haynes method.
Can you briefly describe it? I'm interested.
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