Hi Gang,
I've been driving with a slow coolant leak for some time, but haven't been able to see where it's coming from.
Today, I put it on jackstands to install a wideband O2 sensor, and saw coolant dripping from the rear of the engine.
Anyone have an idea where this is originating? I can't seem to trace it.

(see huge/detailed version of pic here: http://www.kkoop.com/RX7 )

 

either coming from the hose off the rear iron(under the throttle body) to the thermowax or off the thermowax to the BAC valve.

 

Thanks! I'm doing some disassembly on top as well, so I'll check there. Much appreciated!

 

I believe there are freeze plugs in the rear housing and one of them could be leaking coolant into the bell housing. If you don't find a leak in the hoses that Karack suggests, you might have to drop the tranny and check the freeze plugs.

 

Can't tell if it is a Turbo or NA. If it is a turbo, it could also be leaking from your coolant line to the turbo, but if you can't see it, it may be leaking from between the block and the intake.

 

I vote for rear thermowax hose. Happen to me and i thought i had a outer coolant seal let go. Thankfully i found the leak right before i was about to order a entire gasket kit. Or its a freeze plug. You should pressurize the system then look around.

 

If it's not the bac, or thermowax hoses, check the heater core hose/inlet into the fire wall. It is a brass fitting the hose attaches to and it's easily bent or damaged.

 

Oops. just realized I forgot to update with my findings.

Anyway, got a radiator pressurizer kit and under pressure, I could see a puddle of coolant appear just below the block outlet which goes to the UIM - the bitch-to-reinstall hose - in between the primary injectors. Still, I had the outlet plugged and clamped tight so, WTF

Next, I dried up all the puddles, climbed on a stepstool so I could look at the top of the engine while adding pressure. This time I could see it oozing up between the LIM and the housing. So, I disassembled the LIM and found two tattered rubber O-rings. I think the original installer muffed it up.

Now, I have new O-rings in and am re-assembling. Will report back when I pressurize it again.

- k -

 

So, here's the final update. I'll write this as inspiration for those frustrated by chasing leaks.

It CAN be done!

First, after assembly with new O-rings 'tween the LIM and block, I filled and pressurized system...almost immediately, there was a steady drizzle off the passenger motor mount.

RATS! Spent another hour disassembling the top end (just UIM and stuff), plugged the BAC water hose and the block UIM outlet. Filled and pressed again...SAME. I thought it might be the trouble-hose, or my installation of the O-rings, but nope.

Now, while it's drizzling, I search all around with flashlight trying to pin where it's coming from. Nothing on top the engine. Turns out to be the hose connecting the water pump to the Turbo water feed. So, replaced that and put Fuel Injection hose clamps on it for good measure.

Fill, pressure...a lot less, but still dripping...(aw, c'mon man)

More searching found a drip from the top radiator hose at the coolant filler neck. This one was deceptive, because it dripped onto the air pump mount, ran down to the oil pan, ran toward the back of the engine (it's up on high jack-stands) onto the motor mount and down to drip off. Kept me looking at the back of the engine till I got under with paper towels and spent 20 min or so doing a wipe-and-wait trace to the source. So, New Clamp there and try again.

This time, it's still dripping (arrrggghhh), same place, but very very slowly - about a drop a minute. Not that much, really, but now I'm on a mission.

More searching with flashlight and a Ryobi goose-neck camera and I found a drop under the Turbo water tube banjo fitting. Leaking both sides, about once a minute. The water took a different route to arrive at the same place to drip to the ground. Anyway, I tightened it and got the drip to once in 2 minutes, but still leaking.

Fr' cryin' out loud! I ain't givin' up...

Took the bolt off and thought the crush washers looked odd. Closer examination I realized that the past mechanic(s) had not put in copper crush washers, but bronze thrust bearings! ANOTHER WTF moment (of which there has been a constant flow).

Now, put on real crush washers, filled, pressurized and waited. After four hours at 12.5psi, there was no pressure loss and not a drop of coolant under the car.

YAYYYYY!!!!!

Next up, put it ALL back together and begin final tuning of the LTX12, then Off to Emissions Test!

Thanks to everybody, as always, for your help and input!

- k -