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MG MGB Technical - Mini Disaster

Hi guys!!

This is not specifically an MG thread, but i need your assistance!!

I am currently on my hols in South Africa, i have an old mini of estimated 67-70 vintage, judging by the similarities of certain things with my own BGT.

The thing overheated twice the other day, in v high temps, with the water boiling in the radiator (sounded like a kettle!!). After the first time, we cooled it completely and we refilled the radiator. Then drove it soon after the refill - again it boiled over, but we limped the further ten minutes to our destination.

Upon refilling the rad there is now (almost inevitably) a leak! The engine is a BMC, looks to be a 998cc A series, from memory. The system has an expansion type reservoir, which fills into the radiator, and then into the thermostat housing which is of the same design as the BGT thermostat housing.

I have pretty much traced the leak to either the block side of, or underneath of, the thermostat housing, but from the rear - i.e. firewall side of the engine bay. I dont think it is the main head gasket, as the water seems to be leaking before it reaches the head.

The mini belongs to a travelling companions family member. The strength of the sterling against the raand means that a hefty repair bill would be better brunted by us, but if we can determine the prob before having to find a garage, it would be apreciated. I suspect the gasket around the thermo housing at present, but have not been able to get a good look due to space under the bonnet (hood). Also i am reluctant to get the tools out as i am not very familiar with this engine model and we have no manuals.

Any guidance or hints to prob and solution apreciated.

I will be away until wednesday evening, so cannot reply until then, but thanks in advance

~PHIL

Phil

If it has expansion/overflow tanks I would have thought it later than 70. You say 'boiling over', but then talk about leaks. If the water leaks out the engine will eventually overheat and you may well hear what is left bubbling by listening at the rad cap, but that is overheating caused by water loss, not water loss caused by overheating. That might sound pernickity but you have to establish which. If it is water loss causing overheating that should be relatively easy to diagnose - where is it dripping from or steaming from?
Paul Hunt

Phil


It's a long time since I had a Mini, but from your description it sounds as if it might be the bypass hose.

Can't remember it's exact location, but thick it' on the R/H side looking from the front of the car, kust infront of the bulkhead. Connects the head to the block.

The pucka BMC part is a very rigid convoluted pipe and you may have to take the head off to fit it. Aftermarket hose used to be available, which was more compliant, could be squashed up between the studs from the head and the block.


Hope this is of help.

Steve
Steve Williams

The bypass hose goes between the head and block. You can find more information at <a href="http://www.minimania.com">www.minimania.com</a>.
Steve Nightingale

Put some kind of soap in with the water which acts as a water wetter and will help it cope with the heat better before boiling over. Check the rad cap works ok and for leaks like the others suggested.
Daniel Thirteen-Twelve

Hey guys!!

I have had a more studied look at the mini today, as we have been away these last few days. I may have got myself confused with the expansion tank. It may just be a header?? It is a small plastic tank fastened to the bulkhead, slightly above teh height of the radiator filler neck. It has an overflow pipe here, and a second pipe which fills into rad itself. Both rad and tank have filler necks. Its very hard to fill the small tank due to its position (the neck fouls teh rain channel at back of bonnet) and much easier to fill at the rad, i assumed therefore that as teh overflow came from this pipe it must be someform of expansion tank to minimise loss out of the overflow tube. It looks much more like a remote filler to be honest, but its position seems almost daft to me (detrimental to its function). The car definitely does not 'look' younger than 1970....

Anyway, back to the problem. I have been out again this morning. Looking down the engine from the thermostat i can see a small black 'corrugated' tube, below this is the larger diameter tube that goes to the bottom the rad. There appears to be four bolts arranged in a square around the fan shaft at this point, which appear to hold the cooling fan assembly in place - am i right in thinking the water pump is here?

The water when poured from the rad filler neck, is exiting from the underside of the larger hose that goes to the bottom of the rad, at the location where it meets the fan assembly bolts and the small vertical tube (bypass hose??). At least this is my best guess as i can see the water trickling, but only feel where it is coming from. Space is obviously tight, but if i squeeze the bottom of the hose i appear to disrupt the leakage flow, so most likely (to me at least) the water is coming either from this bolt/fan assembly or from the rad hose.

Hope this is making it a bit more clear.

As to the point of whether the water loss caused overheating or vice versa i am unsure. When we took the mini, we were assured that the water, oil, fuel etc was all full. We never checked it - so i have no idea what level it was at really. All i can say is that previously the temp stayed very constant until the day it overheated, so i dont know if any water loss occured in this time. The bubbling sound was the first we knew of the overheating really, although we had monitored the rising temp needle. I can see how the water loss through a worn hose could cause this effect and that perhaps the hose was the cause of the problem?!?

Thanks a lot for your help. I look forward to hearing your continued thoughts...

~PHIL
Phil

Hi Phil

I have a '72 midget which has the 'A' series engine like a Mini. I've just had to replace the bypass hose and it is a pig of a job (no skin left on knuckles). I also have a corrugated hose and this is described in Moss as a 'tempory replacement' part - it is impossible to get a non-corrugated hose on without removing the head or (maybe) the water pump. Once I had the hose off, I could see that it was molded in two halfs lengh-ways and had split along the seam, I'd guess that yours has done the same. As to whether this was caused by, or the cause of, the over-heating I can't say.

I'd think that filling a Mini is the same as filling Midget - you fill the rad to the top of the rad filler plug, and then half fill the expansion tank.

Good luck.

Jon

P.S. althought the help here is good, you may get better A-series help on the Midget pages as they use that emgine. (no offence folks)
Jon Wright

Seeing as you now say you have a water leak - assuming that when you say "The water when poured from the rad filler neck" you really mean "The water when poured *into* the rad filler neck" - it seems a fair bet that the overheating is caused by water loss and not vice-versa!

As to which hose, well, you are on your own. Try and put some kind of barrier between the two. If you use a cloth and it gets wet then the implication is that it is from above i.e. the bypass hose. Any hose usually leaks from somewhere *between* its clamps, but I'm sure someone somewhere had experienced something else.
Paul Hunt

Phil

whichever hose it is you will find it easiest to remove the radiator

this is not as difficult as the books say -

unscrew top hose clips and rmove hose
unscrew the top clip of the bottom hose
and also the heater spur which comes off it if you have a heater, and ease these pipes off the spigots to which they attach
unbolt the radiator top mounting plate
loosen and if necessary remove the 4 bolts which secure the shroud to the rad
using a long socket unscrew the rad bottom mounting bolt - this is difficult to see but is about 4 inches long running from front to rear of the car at the base of the rad
fiddle the radiator and shroud past the fan and out forward and upwards - you need to be patient and you MAY need to remove the shroud first

you will then be able to inspect the bottom hose attached to the rad and change it if necessary

you will also be able to inspect and at least get at the transfer hose

check also the water pump gland for leaks

Good luck and happy christmas

Christopher Storey
chris

Funny, it sounds very much like a plugged radiator I had once on a 61 Pontiac. The car had spent its entire life in southern California and in the 60s, not everyone ran antifreeze coolant - many opted for plain water - but usually tap water with everything else that came with it. Over time, this Pontiac's coolant system became pretty heavily scaled and the tubes in the raditor, having the smallest openings, clogged first.

I am not about to say that what you are experiencing is due to the same problem, but if the car's history seems to be similar to what I just described, you might consider this as a possible reason that your coolant not only overheats but also escapes as steam by blowing out of any available hose leak, crack, or past the radiator cap. I had to refill that system just as often as you describe.

Bob Muenchausen

Hi Phil.

As a seasoned mini owner, let me try to shed some light on the problem. From the sound of most likely the bypass hose has failed, or the main hose from the waterpump to the radiator has failed or is loose.

If the bypass hose is a corrigated one then it's the "easy fit" type which have a limited lifespan of a couple of years. The advantage of the corrigated type is they can be fitted without removing the cylinder head or water pump. The best way to replace the bypass hose is to remove the cylinder head, and take the oportunity to decoke and re-lap the valves, or to remove the waterpump. Either way replace the corrigated hose with decent 1/2 inch heater hose and new clamps. This type of hose is good for upwards of 5 years. This would require either a cylinder head gasket set or a new water pump gasket and about a days work.

The header tank sounds like either something specific to the SA minis or a period mod to try to get more volume into the system. For the simplest and most cost effective repair I would : remove the rad, check for damage and back-flush. Replace the bottom hose and clamps, they don't cost much and it's piece of mind. Remove the water pump, check and replace if necessary. Replace the bypass hose as described. Re assemble everything, refill with water, demineralised if possible, use the minimum antifreeze/corrosion inhibiter. Then look into something like "RedLine Water-Wetter" to improve the cooling capacity.

If you have time take the head gasket route. If you have money to spend get a special 2 core rad from Minispares/Minimania, the Kevlar reinforced hoses, a new thermostat and rad cap, get a head gasket set and do the bypass hose when you have the head off.
Phil Hill

This thread was discussed between 16/12/2002 and 23/12/2002

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