Weird coolant problem, or not?

[ClassyCrusader]

Hey everyone! Glad to join here. Owned a lot of 80's beamers and figured z3's are e30's with the m50 swap already done (albeit a little heavier).
Aaaaanyways ill mention all that in the introductory but for now i need a little help, or maybe I don't?
Let me explain. So had the car for a few weeks now and its been great, no issues what so ever. But I'm sitting last night in my parking spot on the phone while my car's on and bam, steam everywhere all of a sudden. Look at the heat gauge and its not where it should be, was at right (too dark to see how far in the red it was but definitely close if not in it).
So now i think, "Oh great lost a lot of coolant and need to replace a hose now. I'll wait until morning to see clearer"
Morning arrives and i turn my engine on to see if I can find the leak, nothing.
So I wait until its at operating temperature figuring the thermostat hasnt kicked in, nothing.
It idles at op temperature and doesnt budge. I figured maybe the burst last night made me run out of coolant when nothing showed up before but then why does it stay stuck at operating temp? Even drove it around my complex a little to instigate something new but no it was happy where it sat. When this happened to my e28 535 I couldnt get out of the parking lot before it got too hot. At this point im just going to drive down to the store and get coolant, why not? Even getting the coolant at this point seems just like a safety measure.
Anyways looking to you guys for help, anyone know something I don't? Do these hoses magically go back together when cold? Or did I not let it get hot enough? Or what? Hoping someone with a similar problem can shime in

 

[ClassyCrusader]

Update: dilled it up with some coolant, drove down to the gas station and everything seemed fine. Checked the fluids while i was there and the oil was bone dry, found what caused the overheating.
Got some more oil and drove home with the most load I could put on it to make sure all was well and right when I pulled into my spot, it began to overheat.
Good, I thought, now i can see where the leak is. Popped the hood and turns out there's a crack in the radiator. Its visible and easy to get to so I'm going to jb weld it in hopes that I dont have to replace the whole radiator. Anyone done this before or would advise against it? Dont have a whole lot of money right now so figured its worth a 20 dollar try.

 

[colb]

As good a reputation JBWeld has I wouldn't use it for this repair, just too risky, if it fails you dont want head gasket problems to add to the repair costs. If the radiator is to be replaced then it would be prudent to change the water pump and the thermostat, more money but worth doing when the radiator is out. Don't forget the plastic filler, expansion tank thqat sits at the side of the radiator, these have a reputation of splitting, so replace that with the radiator.

 

[ClassyCrusader]

Well the jb weld held and refilled the tank but its still overheating. Maybe the water pump or thermostat?
Its running fine So dont think its a head gasket.
Any ideas?
Its bone dry under the car when I check

 

[colb]

Sounds like its time to change out the waterpump and thermostat if its still overheating, with new parts you will be starting on a level playing field, nothing else left to change after that, only the radiator, are all these parts the originals, any evidence of them being changed before?

 

[ClassyCrusader]

Its funny im actually sitting in front of the car now with a new thermostat hoping for the same thing. The water pump is leaking a bit but still working. I only just realized I need a bigger wrench to take off the fan clutch, seems nearly impossible otherwise = p

 

[Palmetto]

32mm if I recall. Don't forget it's a reverse thread too.

 

[Vince]

It’s so cheap for a complete cooling system on a E36/Z3 it really isn’t worth blocking up your waterways with a load of gunk.

I bought a Nissens radiator and nice new red hoses plus a premium quality water pump and thermostat for my Z3 and with discount codes and eBay auctions and I got the lot for under £100.

But I have an E36 also and changed the cooling system on that one and still lost fluid and it was only the expansion cap but buy genuine for that part as the fake eBay ones don’t hold pressure.

 

[Palmetto]

But I have an E36 also and changed the cooling system on that one and still lost fluid and it was only the expansion cap but buy genuine for that part as the fake eBay ones don’t hold pressure.

I have the same problem on my E36 318i. The rad, cap, thermostat & pump have been been replaced but its still losing coolant. There are no leaks that i can see. I’ll try putting the original cap back on and see how it goes.

 

[Vince]

A good way to tell is if looking underneath the cap the fake will be orange and the genuine item will be black.
Also the new genuine BMW caps have a warning diagrams in yellow on top.

 

[ClassyCrusader]

Update:
It was indeed the thermostat, back up and running. When I get some more money in I'll be redoing the whole cooling system. Thanks for your advice guys! And 32mm was right, thanks Palmetto!