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MG MG Y Type - Water use

After a year and a re-built engine I do not appear to be any closer to the solution to the water consumption in my YA. Before the re-build it was 1 litre per 10 miles and it is now 1 litre per 30 miles.(excuse the mixed units but I use litre milk bottles and the odometer is in miles)

The mechanics have tried some additive that makes leaks fluoresce and found nothing. The water just seems to boil away. Is this normal?

Is the engine running too hot?

Appreciate the collective wisdom, thanks in advance.


An steam present in the exhaust? Could be a cracked valve seat in the cylinder head.
Scott Barrow

Besides any steam in the exhaust, another few possibilities are:
* leaking core of radiator - a small pin hole will cause loss of water at fairly rapid rates!
* check the connections of all the hoses - if they are just on the metal of the pipes when tightened up with the clamps you may get steam escapes.
* under your radiator cap (which should be tightened down snuggly with one of the nice Radiator Cap spanners now available from Regalia Sales at there should be an 'O' ring. If this is not there, or is ineffectual, again you will get loss
* check the radiator drain cock tap and also the one on the block for leaks
* when the engine was overhauled, were the core plugs all replaced? A badly fitted new one (and they are pretty nastily sized now) or a corroded old one will also cause loss.
* Have you had the cylinder head re-torqued after the rebuild? If will need re-torquing after about 350-500 miles.

It took me about 7 months to trace a small leak on my MG MGB engine that was steaming water all over my distributor!

Happy hunting.

Paul Barrow

I think that this system is not a pressurized one. I would put a small catch tank on the radiator overflow and see the amount you collect. I once had a TD that would seek it's own water level . This appeared too low and I was constantly adding coolant. I found after a run it was spurting out the overflow. I put a new O-ring under the cap and a permanent catch bottle in place. As the motor cooled it would draw the coolant back into the system.
This solved my problem.
conrad sanders

There are details of a catch tank as mentioned by Sandy on this website. Go to Technical Centre - Hints & Tips - Radiator Expansion Tank, and all will be revealed.
I fitted this system to my Y a couple of years ago, and it works very well.
Bill Bennett


When do you fill up? If you measure cold and fill up to the brim, you will always think you lost fluid.

After panicking everytime I checked cold, I listened to Neil Cairns' advise (I sometimes do) to check when warm, and when you can SEE fluid, you are all right. Now I only fill up for a long trip, just to be sure. I know most of it will be pushed out, but when cool I can always see fluid, so no shortage there!

The big tank on top of the radiator IS your expansion / catch tank. If you fill the expansion tank when cold, the expanding hot fluid will push out the surplus.

With the open system we have sealing is less critical then the pressurized systems commencing from the TF XPAG.

Do check the steam from the exhaust and tightening of the headbolt tips etc, but also try to "let it find it's own level" as Conrads says. My Y5888 found it, too.

Willem van der Veer

Murray - I suspect that what several responders have stated is what you are experiencing. See the article, Expansion Tanks, Cooling (should be Coolant) Recovery Systems and How The Cooling System Works under the Other Tech Articles section of my web site at: In that article I cover the cause of loss of coolant (as has been stated above) and how to install a recovery system. Note, the pictures of the pressure cap applies only to the TF and later MGs. The Y types have a non pressurized system so adding extra sealing capability to the filler cap will not do you any good other than making sure that any expanded coolant is forced out through the overflow tube and not around the cap. Cheers - Dave
David DuBois


As a 100 to 1 shot could be a nasty situation.Maybe a tiny leak through one of the cylinder bores via corrosion? Have seen this on a TF which was bored out only 40 thou.


Just to bring this thread to a happy conclusion; this water consumption problem appears to be solved. The water pump bearings were shot so the pump was replaced and the water consumption is now down to 1 litre per 200 miles.

Thanks for all the helpful suggestions.


Thanks for the feedback and congratulations with the result. I guess you should now try to let it find it's own level? One litre per 200 miles still seems a bit much?

Just curious why the mechanic failed to spot an apparently obvious leak and fluor additive?
Willem van der Veer

I would suspect that a check of your mechanic's wallet would indicate where the dye check went. With the volume of water you were loosing it should have glowed all around that area.
Still with a coolant loss of a litre per 200 miles you still have a situation . Try a coolant recovery system . Does it bubble and regurgitate on shut down after a decent run? This can indicate that it is trying to settle it's level.
conrad sanders

In defence of the mechanic, who is a thoroughly decent guy (and I have an invoice totalling 0.00 for work done, to prove it) I think the issue was that the wear in the pump bearing meant that the water was not circulating properly and was simply boiling away - not leaking anywhere.

I may still be over filling as I establish its level - I may have to make a longer radiator dip-stick or, as suggested, measure when hot to find if it is actually using water. It was venting via the overflow when I checked at one point on the run home.

I guess I am still in the paranoid-about-running-out-of-water phase, so tending to be over cautious.


This thread was discussed between 29/06/2008 and 21/07/2008

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