MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MG Y Type - Overheating problem

This is probably a very simple problem, but one which, as a novice, I would welcome some help with. I took my YA out for a spin up the Dales this afternoon. After about 45 miles and a fairly steep hill there was a sudden loss of power and the engine cut out. I looked under the bonnet, but could see no obvious problem and the car had been running well up to that point. I left it to cool down and after 30 mins or so it started and I continued my journey. After about 7 or 8 miles the same thing happened. I waited for a short time for it to cool slightly and set off again, this time only managing a few hundred yards before it ground to a halt. As the traffic was building up I decided to call out the breakdown service. I always check things like the water and oil level, fan-belt etc before setting off, but that's about as far as my mechanical knowledge goes. I use the car most weekends and have covered many miles without any problems. The car will start and run after being left, and when running the engine sounds fine. The breakdown man couldn't offer any suggestions, but it seems to be some sort of overheating problem. I took it out on much hotter days than this last summer without any problems. It doesn't have a heat shield and I had just topped up with leaded petrol from a non-local garage. Any ideas folks?
Andrew Adamson

I had the same problem with Y5710 I thort it was fuel evaporation so I put a heat shield on the manifold but this didn't help much so I went throw all sorts before I got it down to the spark plug caps it had "L" shaped ones with suppresses in I changed them to striate throw ones with out the suppresses and it's been fine since.
John
John

Thanks John. Would the spark plug caps be affected by heat?
Andrew Adamson

Well I didn't think so but it worked.Has yours got the "L" caps? It may all so be the coil over heating.
John

Andrew,

Do you have a heat shield behind your carburettor? If not, I would guess that you have vapourising fuel.

Solution is easy - get a copy of Fitting a Heat Shield from Regalia Sales and get someone to fabricate you one up! They are invaluable.

Regards

Paul
Paul Barrow

I suspected fuel vapourising, as the carburettor was very hot, as was the fuel pump. I should have mentioned that when I restarted the engine (after allowing things to cool down a bit) the fuel pump ticked away very noisily for a while, whereas normally you barely notice it. I ran the engine for about 20 mins this evening and the problem didn't recur. However, I'm reluctant to take it out on the road again as it can be very dangerous when the engine cuts out without any warning. (Especially when I can't even put the hazzard lights on!) What I find strange is that this never happened last summer when it would often spend long periods in traffic jams on very hot days. I'll look into getting a heat shield fitted, but in the meantime any further advice or comments would be gratefully received.
Andrew Adamson

Was the petrol pump ticking fast when it stopped?if it was it is probably evaporation
My spark plug Cap problem got worse over several years until it wouldn't run at all.
John

I didn't notice the fuel pump ticking over when it stopped, although it might have been. When I ran the engine tonight it didn't get really hot, but if you put your hand on the fuel pump you could feel it splutter a bit every so often, although this may have been because the engine was just idling. I revved it up a few times. I wondered if there may have been some contamination in the fuel, since I'd filled up (with leaded) at a garage I've never used before, but again, I wouldn't have thought this would be a heat-related problem. (and I'm assuming it is heat-related)
Andrew Adamson

It may be the petrol I got some on the A19 (BP Garage)and it ran terrible I think it had water in it.
John

I had a similar problem with my YA, all of the symptoms of fuel vapourisation in our hot summers and rather poor quality fuel. On the advice of a friend who had the same problems wirth his YA (and, in turn, the advice to him from an "expert") I fitted a new coil (even the cheap ones from the "spares outlets" are incredibly more efficient than the original one that was, in my case, still fitted) and completely overcame the problem. I have never had it fully explained to me but
somehow the the much more robust sparks must overcome the potential problems caused by fuel vapourisation.
Barry Bahnisch

I believe that overheating of the carburettor was not uncommon on early BMC A series engines and an insulated gasket was available - basically a thicker block of asbestos sandwiched between two composition gaskets to act as a heatshield between the carb. and manifold. Part number was BMC 2A152 I believe. Presumably this stopped heat travelling across the manifold - carb. joint. Not sure what the current gasket for the XPAG is like.
A heat shield is also a good idea too.
David Mullen

David is correct. The Data sheet Fitting a Heat shield describes how some cars will benefit from merely having an aluminium shiels, other an insulation block, and others both. The block you need is the one for the BMC Mini, however, you will need another 2 gaskets too, possibly even to renew all of them.

If you go for the block and heat shield, as I have, you will need slightly longer bolts from the air cleaner body to the back of the carburettor.

A heat shield is also available for the YT we believe from Brown and Gammons - it is the same as on a TD search on their website using "Heat Shield" and not "Heatshield".
Paul Barrow

Many thanks for all your suggestions. I think my initial thoughts of fitting a heat shield seem to be confirmed, but it is useful to have a few alternative suggestions in case the problem remains. I've now received a copy of the leaflet on fitting a heat shield, but it doesn't really look like a DIY job for those with little mechanical knowledge. I know there are people here who can rebuild their gearbox at the side of the road using only matchsticks and rubber bands, but unfortunately I ain't one of them. The leaflet doesn't actually show how the heat shield should be attached and I wondered if anybody could maybe send a photo of the heat shield in situ, and/or mention any problems likely to arise during fitting. I'll probably have to have it fitted at a local garage, so I'd like to keep head-scratching time down to a minimum.
Andrew Adamson

Hi Andrew

If you look at the drawing you will see that there are drill location markers for three holes, centres aligned vertically with two smaller holes and one larger hole.

Fitting is simply unbolting the carburettor from the inlet manifold (you will have firts removed the air filter and the body). I would also suggest having a pair of new carburettor gaskets to hand (they are the same size as the ones on a BMC A series Mini engine).

Ensure the face of the inlet manifold is totally cleaned off from any old gasket material and also the face of the carburettor body, and that they are both flat. One gasket against the inlet manifold and the heat sheild, one against the other side of the heat shield and the carburettor body and then simply bolt the lot back together. As Haynes manuals would say "assembly is the reverse procedure of removal".

If you are fitting an isolation block too, this requies an additional gasket, and a longer set of bolts. This is all covered in the leaflet I believe from memory. My copy is enroute to me as are the digital masters and my car! If I am wrong, which I doubt, I am sure I will be corrected, but I believe you will find the above to be correct.

The hardest part for me was making the heat shield, so I cheated and had it made by our toolmaker at the place I was then employed. He made a craftsmans job of it and it looks lovely. More to the point, it is very efficient too in curing the vapourisation problem. Like I said though, I also use anisolation block.

Paul
Paul Barrow

One further thought (and sorry for asking so many questions), will the heat shield also keep the fuel pump cool? I notice that mine seems to get to the same temperature as the carb (whether that be hot or cold), even though it's mounted in the normal position, ie not near the manifold.
Andrew Adamson

Assuming by "mounted in the normal position, ie not near the manifold" you mean on the side of the battery box, the answer is No it wont. The heat shield is designed to merely cause the heat from the manifold to be disipated rather than being absorbed into the inlet manifold causing the vaporisation of the fuel before it enters into the inlet manifold.

When you say it "gets to the same temperature as the carb" which end do you mean? If you mean the outer end, you may be feeling the effect of the contact breaker - I must admit I have never noticed this before myself so I cannot comment. If you mean the end where the fuel enters and is pumped over to the float chamber, I would suggest that you should use a heat shieled petrol pipe from the pump to the carb. It probably was not one of the cleverest designs to bring the fuel up in a copper pipe directly behind the engine, but provided the pipes and unions are all in good condition, I do not think you have much to worry about here.

Fit the heat shield first, then if you still have problems use an isolation block too. I would suggest that when you do this, you have the carburettor set up by a mechanic who understands SU carbs and what he is doing, to get the correct idle speeds and mixture settings. While he is doing this he should also check to ensure that you are using the correct needles (see Technical Data Sheets from the Technical Centre section) and he should also examine the other parts of your carburettor and float chamber/valve set up for wear and fit, replacing where necessary.

Paul
Paul Barrow

Andrew, you have received a lot of good advice above but I would be more suspicious of the SU Fuel Pump. The insulation on the windings of these now very old pumps breaks down and is worse when they get hot and they simply stop until they cool down. Your best bet is to fit a modern electric pump down the back of the car, leave the old SU connected for originality but disconnect the power lead and the new pump will pump cool fuel through the old SU and up top reducing vapourization problems. Also make sure you fit a good fuel filter between the tank and the new pump. I have done this to our TD and YT and never have any dramas and no heat shields, on days when it is 40C in the water bag.
Cheers Richo YT3208.
Richard Prior

Hi Richard, good call. Andrew also consider sending your pump to Burlen as they do run an exchange & rebuild scheme - so you can have the best of both worlds - a new pump and an original in one. They are in Salisbury Wiltshire, UK so you are ideally placed to take advantage of them - compared to me now (I used only to be 15 miles from them!).

Paul
Paul Barrow

Again, many thanks for all your help. The car is currently having a heat shield fitted (along with new rear brakes and a general service), although I haven't opted for insulation pads, due to the extra work involved in lengthening/shortening cables, hoses, etc. It was even suggested that the problem may be the radiator core, which appears to be the original one, or at least a very old one. Being from Yorkshire, I'm reluctant to replace expensive bits unless I am reasonably sure that they'll cure the problem, so for now it's a case of keeping my fingers well and truly crossed. Thanks again.
Andrew Adamson

After collecting my car from the garage, where it had just had a neat-looking heat-shield fitted it broke down yet again, just a few hundred yards from home. As it was a busy, narrow road, I could only pull into a cul de sac. This time, the carbs were only cool, but the fuel pump very hot. Whilst waiting for it to cool down I looked through the workshop manual and found, in section H4, that a blocked fuel pump filter would produce the symptoms described. The remedy was of course to clean the filter. However, my fuel pump seems to have no filter. After disconnecting the inlet pipe and blowing through it, and reconnecting, the engine started and ran much, much smoother than it has done for a while. I believe it's possible to add a filter in the fuel pipe. Has anybody tried this and are there any particular problems associated with it? Would it be better to try and find a fuel pump with inbuilt filter? I can't help thinking that the last tank of fuel I bought may have been contaminated in some way.
Andrew Adamson

Andrew

Great news that the carbs /inlet was cool.

It is fairly easy to fit an in line fuel filter - after the fuel pump, but it is better to do it before!

Doing it after the pump will stop stuff clogging up the needles and valves in the carb & float chamber. Before will protect the pump!

Doing it after - go to Halfords and get one for a mini, and a short length of petroflex hose (of the right diameter) and 2 clips. One end on the output of the pump & clip it, one to one end of the filter & clip it, existing pipe on the other end of the filter and clip it. Do not shorten or cut the existing pipe as you may want to take the filter off when you get the pump sorted out.

Take care which way round you fit the filters - some are directional!

Doing it before will be more difficult because of the brass pipe and couplings.

Going totally from memory though, I think, if you have the proper standard SU fuel pump (thoroughly reliable normally) there is a built in one - it should be underneath the union where this enters the body of the pump.

Best bet - ask Jack Murray (registrar@mgytypes.org) as I know he has dismantled loads of these!!

Paul
Paul Barrow

A similar problem occurred to me and was caused by strips at the bottom of the regulator touching and causing a temporary short. With heat, they bend and touch each other. When the car cools, they get back in their original position and the short is gone, hence the car starts. You may not have that, but it costs little to check.

As to carburettor shields, I don't think they help. In my TD I have installed temperature gauges on both carburettors and the front is always warmer than the back one, because it gets the heat from the radiator. However, those insulators between carb and manifold prevent gas boiling, which I never have in Lugano, which I believe is considerably hotter than Yorkshire!

Denis
Denis L. Baggi

Andrew

Sorry to arrive later on in your saga of the hot spots of the Dales...

I have some spare pumps with filters and a (partially decrepit but working) heat shield on the YA. If you fancy a test run up to Ripon, give me a call and we can compare failure points!!

Andrew
Andrew Coulson

Thanks Andrew, much appreciated. I don't think I'll be able to get to Ripon during the next couple of weeks, but I'll hopefully see you at Clotherholme Farm on the 11th July, so we'll be able to compare notes then.
Andrew Adamson

This thread was discussed between 16/05/2004 and 19/06/2004

MG MG Y Type index

This thread is from the archives. Join the live MG MG Y Type BBS now