Chasing coolant loss

[ChrisP98]

Hiya, apologies if this is a repost of a common issue, but I'm after some advice regarding a coolant leak that I can't seem to find.

I have a 1998 1.9 (M44) Z3 with 130k miles that isn't a big fan of keeping its coolant inside the cooling system. Thus far I have replaced the rad, hoses to and from the thermostat, the thermostat itself, and the water pump. This, temporarily, cured the coolant leak, but it returned today. The new leak appears to be towards the rear of the engine bay. I have got the awkwardly-placed plastic coolant flange part ready to be installed at the weekend, however I'm not certain that this is the source of the leak. I was hoping someone could advise me of other aspects of the system that are prone to leakage/should be replaced as preventative maintenance, and any handy tips or tricks would be much appreciated!

I'm learning to work on my car as I go along, and improving with every new job I tackle!

Cheers,
Chris

 

[colb]

If the leak is at the back of the engine it would most like;y be the plastic pipe at the rear of the block, the O ring probbably gone hard or cracked, age related as its deteriated through heat cycles and age. Since you have already dealt with the front of the engine it only leaves the rear end of the engine being suspect.

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[IainP]

Agree, that little connector is prone to all sorts of problems.
If it’s not the O ring as Colb suggests, it’s likely a crack in it. I’ve seen cracks at the O ring groove itself, the underside of the body and where the hose clip is fitted.
Be Very Careful when removing it. If it is cracked it can break up, particularly if the crack is at the O ring groove. You then have the lovely job of trying to remove a bit of plastic you can’t see, with no access for a decent screwdriver. I ended up heating and bending one into a sort of right angled pry tool.
Make sure there’s no bits left in the hose too.

 

[IainP]

This is what one of my sons 1.8’s looked like, this was a bit older than yours.

 

[Pingu]

Get yourself a coolant pressure tester.

Google

 

[Alin S]

This is what one of my sons 1.8’s looked like, this was a bit older than yours.
View attachment 210007

Mine looked exactly the same. If the leak is at the rear of the engine, that’s the most probable culprit.

let us know how it goes!

 

[Alin S]

It was a bit of a pain to get to through. You basically have to rest on the engine to be able to get access…