2007 Coolant leak/Using water

Good morning everyone, first post , I'm Luke and have had my Jimny for three months.

Apologies for the long ramble. Hoping someone has experienced this before and can advise how bad the repair is ! 

I brought it as a non runner and advertised as having low compression. After a few days trying to get it to start, I bit the bullet and fitted a used engine. As there was signs of head gasket failure, in the expansion bottle, I kept the thermostat, fan, hoses and water pump off the donor engine. Washed the radiator out . Initially didn't use any water, temp gauge moved and sat just below the symbol on the gauge. 

Currently using plain water in the system as wanted to do a few flushes to make sure any emulsion was removed . 

However now I've started using it daily the water level is dropping, I've topped up the radiator twice and the bottle is empty in a few days. There are no visible leaks from the engine bay, hoses , radiator all good. 

This morning I've used the heater for the first time  and I've got water running down the gearbox and pooling on the floor . 

I'm suspecting the heater pipes or matrix underneath the dashboard have failed. Has any one experienced water dripping in this area and then found a similar fault ? 

The only thing I can think off because I'm using plain water , the coolant could be evaporatoring slightly during use and we have had a very hot May, but this is the first leak I've seen and wondering how bad it is to strip the dashboard out ?

I've heard some people say it's a good 12 hrs work. I'd be happy to do it myself, have changed the engine, clutch etc myself so do have some mechanical ability ,but wonder if it will go back
together nicely and spoil an otherwise nice car ?

Realistically the car has 5 months MOT, will need a bit of welding and wondering whether to cut my losses or treat this as part of the Jimny adventure. 

Thank you reading. 



 

you could test the coolant for exhaust gas, could tell if there is a internal leak. Most likely head gasket or head leak.

Sold my nicely working m13 engine to a friend with coolant issues so it is a known problem.

I would without a doubt swap to a liana or other m16 engine if there was any indication that my m13 had a problem as the car is so much more usable with the extra power.

If the heater matrix is leaking as much as you say it is most likely what your problem is.
It can be swapped without removing the dash, from the underside cant it? 
there is no hoses inside the car for this, you can see the matrix flanges/hoses on the firewall engine side..
Not sure if there is an AC it might be more troublesome, i havent done this myself in a gen3 jimny so sorry if my opinions here is of no help..

as you say there could be other external leaks as well but they should be visible if so when they get big enough. Or maybe if the coolant gets into the cylinders but that should give some smoke.

The pipes into the matrix are just crimp fitted and won't do with being disturbed, I found this after an engine out job. Proper big job to get at as everything has to come out. Worth persistence though.

Thank you so much for everyone's help so far, really appreciate it. 

I've been out during work and there's no mega puddle underneath ,radiator is still full and the bottle was empty. I'm certain I've found the leak ! One of the hoses on the rear of the cylinder head has a slight crack in, I know these were a pain to fit during the engine swap, one of them has been disturbed before as the spring clip has been replaced by a jubilee clip. 

Hopefully a new pipe will cure it and I've got away without any interior work.