I found coolant on the floor under the water pump this morning when I went to bleed the clutch fluid. Today was supposed to be back on the road day...

Took off the wheel arch lining and started to fumble with the pulley bolts and noticed a water transfer pipe O ring sitting on top of the trailing arm.

So I swapped ends and got the thermostat and inlet manifold out again. Pulled the water pipe and the O ring was snug in its groove. So the one I found was from the old broken pipe (that wasn't leaking but came apart when i pulled it out of the engine).

I've now got the engine mount, water pump pulley and drive wheel off, but can't see any obvious sign of the water pump not being seated correctly on the block. It's a new pump and gasket. Do you think I should take the pump off and put it back on, or is there somewhere else the leak could have come from?

 

When I got the pump pulley and friction wheel off the pump looked to be seated well and there was no sign of coolant around so I didn't take it off.

I put the engine back together apart from the wheel arch liner to see if I could see the leak with it running.

Saw a tiny drip coming out of where the water cross pipe goes into the back of the pump. Will take the thermostat / inlet manifold off again tomorrow and try the new O ring I got in my head head gasket kit. The pipe is new and came with an O ring, but maybe it’s slightly too small.

 

Two hours later and and not a single drop had dripped. Ran the car for 5 another mins to warm it up and then with the water pump going for a minute and no drips. So I'm pleased but not any wiser. Have torqued the engine mounts again. Will move onto clutch bleeding tomorrow and hopefully a test drive (which was today's plan).

 

Left it overnight and now there's a few drops under the engine and on the water transfer pipe where it goes into the back of the water pump. Will ignore for now and get back on the road to see how it goes. Will find a weekend in a month or two to swap the o-ring.

 

I hope all your work will soon pay off. Way to keep persevering Craney

 

Just back from a test drive.

Overall I think I did it.

It drove really nicely but idled very badly.

It’s very unhappy about having a faulty oxygen sensor, but there’s new ones arriving this week so that will sort that out (the sensor really didn’t like being sprayed with fuel when the engine was misfiring...)

 

There’s a bit of coolant leaking from the water pipe. Any idea why a new one would leak?

I’ve got a spare o ring from the head gasket kit I bought, so will try that when I have a spare weekend. Will watch coolant level until then...

 

It seems like you know what you're doing so I hesitate to ask this. Did you lube the o-ring before installing the new water pipe? There have been posts here about o-rings getting pinched and leaking when not properly lubed.

 

I put some rubber grease on it. I've been wondering if that's what caused the problem? There was no trouble installing it.

 

Another problem is small bits of plastic that break off of the old pipe when it is removed. Of course, this shouldn't be an issue if the water pump was replaced at the same time as the water pipe.

 

I think I solved my water transfer pipe leak. Just noticed a single drop hanging under the back of the engine in line with the thermostat.



I felt around under where the thermostat meets the water pipe, and it is wet with coolant. So the leak is at the top end of the pipe and (mostly) running down towards the water pump before heading to the ground.



The O ring at the top end of the pipe is on the thermostat, not the pipe itself. So it is the original o ring. Will change that for a new one tomorrow.

 

Glad you got it figured out.

 

Got it done in three hours but it's the wrong O ring (fractionally small I guess). Will go to MINI here tomorrow to get one of these: https://www.ecstuning.com/b-genuine.../o-ring/11518613804/