Irish Mini Owners Club

So I bring her down to go fonthill for the test. The car is at the first stage and during the emissions test, the tester is alerted to a water leak. On foot of this, the car is reversed from the lane and the test aborted. I get called to the desk and am told that when carrying out the emissions test, the engine developed a leak near or at the expansion bottle.
She appeared to lose a fair amount, from what I saw. I asked for the bottle to be topped up and went on my way. On the short journey home, I heard strange noises from the engine and steam would appear whenever the car was stopped. Also, cold air began to come through the heater. The temperature gauge read normal all the while. When I returned home the expansion bottle was still full, but steam was coming from the block and through the oil filler. After an hour, the expansion bottle was empty with no sign of a leak anywhere. I checked the oil and the level is normal, with no sign of water contamination. All of the pipe work appears ok. Anyone experienced similar, or have any ideas?

Could be a head gaskit or stuck thermostat or a blocked rad.top it back up and leave it run for a while with the bonnet open keeping an eye out for leaks

yea, if the water is leaving the bottle an not hitting the ground its either in the engine or steaming out to the air.. neither is good, both are fixable.

Just ran a pressure test on the engine which revealed a loose top hose. It now appears leak free, but the temperature gauge is reading very high.

it could also be that the impeller on the water pump has stopped working and isn't circulating the water around the engine

Steam from block and oil filler would sound like head gasket. When you say you "filled " the expansion tank do you mean to the brim or to the MAX.

It looks as though there is a blockage somewhere in the system, which caused a probably already slightly loose top hose to loosen further under high pressure during the test, thus causing the leak. Having tightened the hose, the blockage has remained, causing poor coolant flow, resulting in the high gauge reading. Something else I noticed, was the top hose was hot, but the bottom hose not nearly as hot. I just hope it's not the head gasket!

the top hose will be hotter, heat rises! if the water pump is gone it'l be just like a blockage
compression test to check the head gasket
take the belt off the water pump pully and turn it by hand to see if theres anything amiss

woody wrote:Steam from block and oil filler would sound like head gasket. When you say you "filled " the expansion tank do you mean to the brim or to the MAX.

It was topped to the max, then pressure tested. Some fluid was lost through the top hose and when removing the pressure tester. The expansion bottle had emptied after this, was filled again to the max, ran engine and still overheated although the level did not drop. I haven't checked today on account of the weather, but car is off the road for the moment in case gasket is gone.

daniel garry wrote:the top hose will be hotter, heat rises! if the water pump is gone it'l be just like a blockage
compression test to check the head gasket
take the belt off the water pump pully and turn it by hand to see if theres anything amiss

The engine did make an unusual noise, which lasted between 5 and 10 seconds on the drive home. This could have been the pump giving up I suppose. Something else was a gurgling sound from the expansion bottle after switching off the engine? I'll see about getting a compression tester and go from there. Thanks for the feedback.

Just ran a compression test. I'm getting a steady reading of 175 p.s.I. (12 bar) across all four cylinders.
The head gasket would appear to be sound. I'll check the thermostat when it stops raining.

Thermostat functioning.
The finger of suspicion points to the pump. When I had the belt off, the pulley would rotate with small resistance felt, no noise. I think I'll whip it off all the Same and check the impeller.

It's an mpi right?
The expansion bottle cap does give up sometimes leading to your symptoms so start with replacing that. When you top up you only need to fill half way up the expansion bottle and make sure you're doing so with a 50/50 mix of water & coolant. The mpi runs hotter than the previous minis and pure water doesn't cut it.

It's a multi point car, yes. Are those caps available from a motor factors? I'm going to flush the engine when I get a chance, I'll then re-fill the system 50/50. It would probably be good practice to replace the thermostat either way, so I'll do that too.

Should be able to get them at the motor factors as they were a common mg/rover part, make sure the thermostat you get is a 92°C item.

Today I discovered the overflow pipe stub on the thermostat housing had been blocked causing the expansion bottle to fill right up, which explains what the nct tester described as coolant escaping from the expansion bottle cap. I had already flushed the system in both directions, ran a cleaner through and fitted the new thermostat, and with the overflow clear again I have good warm circulation throughout, greatly improved cabin heat and most importantly, the temperature gauge is sitting bang in the mid-range. Problem solved.
(Hopefully, it is a mini after all!!)

Well done, good to see a result