M52 cooling problems

[L8 apexr]

Hi guys,broke the upper rad outlet off the plastic rad a couple of weeks ago so I gathered an ebay aluminum e36 rad,metal impeller pump,IE electric fan,temp switch,thermostat,hoses and tensioners.
Have everything swapped in and had some problems today with the car overheating just in the garage.I think I have all the air out or at least close,the heater core is nice and hot and the car stopped taking coolant.When idling the temp will slowly rise despite the fan being on(not wired yet,get to that in a minute)and continue up until I shut it down just before the red.If I rev and hold about 2500rpm the temp seems to stay at approx. 3/4 on the gauge,if I let it idle back down it will start to climb again.I noticed there's a big temp difference between the lower and upper rad hoses,how normal is that?.
The IE fan is only 12"(I thought it was a 14 when I ordered it),research prior to picking parts seems to indicate others have used this fan and the stock aux fan only with no problems(I didn't reinstall my clutch fan as I think it was part of the problem why it overheated and then the rad failed).Before I order a new clutch and blade I'd like to know if I have something else going on the 12" fan is fine once whatever else is going is sorted.
The previous owner did the swap and completely removed ALL A/C parts and some of the wiring isn't the best and I completely suck with wiring so I took some pics of the possible wiring connectors I have remaining.Yes I've read all the fan wiring threads but need some help still,sorry in advance for my lack of electrical ability.:oops:

[Link]

I am not fully sure what you are asking, but I am running a 16 in SPAL fan and once I got my coolant fully bled I have not over heated. I do get a little warm sitting at an idle in traffic or creeping at 5 mph. I think 12in sounds to small.

Wiring, read the official fan wiring thread in this sub forum.

[L8 apexr]

To try and decide if the fan was too small or something else is going on I just took it for a spin,driving 40+mph in 4th the temp went to the 3/4 mark and stayed there.The fan wasn't wired yet and slowing for an intersection(route had no stop lights on purpose)saw the temps rise even further.
I don't think the fan is the real problem(it still may be too small)as the moving car should've kept the temps normal.There's no smell of coolant out the exhaust nor white smoke,I'm hoping no damage to the head gasket.With the old rad and clutch fan the car stayed right around the halfway mark creeping up to nearly the 3/4 mark when stopped in traffic for awhile and cooled right back to the halfway once moving.It overheated(in grid at an autox event) before the rad failed,I'd chalked that up to the clutch fan failing but....
I really need some help/guidance here,summer is short up here in Canada and I'd like to drive this thing before its time to put it away for the winter.

[butters]

Might be worth pulling out the thermostat to verify that it's functional or just swap in another new part. Is it the correct thermostat? Even with an M42 radiator my 24v runs just below the middle mark while driving.

The t-stat allows flow into the radiator based on temperature. The only other thing that comes to mind is of course whether there is air in the system somewhere. Try bleeding with the car on an incline or the front end on ramps/jack stands.

It overheated(in grid at an autox event) before the rad failed

Have you checked compression or looked for signs of HG issues (oil and coolant visually)? After overheating at autox and now going to or beyond 3/4 on the temp gauge multiple times, unfortunately I would be highly suspicious of the integrity of your HG / head sealing surface.

[L8 apexr]

I did all parts changing,coolant refilling and subsequent engine running and coolant bleeding with the front of the car on stands.No more bubbles in the coolant being released,no signs of oil/coolant cross contamination,no coolant out the exhaust and I just pulled and changed all spark plugs.All were nice and tan coloured with no signs of coolant steam cleaning.
Car has only made 1 autox run in 3 yrs so the abuse is minimal(barely driven it more than a couple thousand miles in 3 yrs total actually).

Looking back I've smelt coolant when warmed up at the front of the car but could never find a leak,was planning on the coolant system getting an overall shortly anyways.I did add a small amount of coolant before the event which I was blaming on the leak I couldn't find.
Btw I don't have any heat in the cabin now,pretty sure it worked before but I've not had it off full cold in a couple of yrs so I'm second guessing that part.For sure no heat combined with overheating is a clue to an air lock but the heater core is hot and I can't seem to get any more air out.Plus the previous owner was a tard so its possible the heater core isn't even hooked up to the vents.
I just ran it again after completely cooling from this morning and the rad gets hot on the upper drivers side but for sure the t-stat isn't opening and sending coolant thru to warm the rad/lower hose until its getting close to the 3/4 mark.The 71 degree stat sounds too cold for street use but should I swap it back in??.Not crazy about draining coolant and adding air back into the system but....I'm getting desperate.
I booked it at an import shop next week to be pressure tested to rule out/confirm a HG issue or otherwise.

[L8 apexr]

Swapped in the 71 degree stat today and all seems well now,ran it with no fan until a little over half on the gauge and the fan cooled it back down to a little over 1/4.Once I get the 80 degree fan switch wired it should stay good.
That's the good news,the bad news is one the throttle is given a healthy blip I'm getting oil smoke on the overrun which its never done before.I'm thinking cracked head with vacuum pulling oil into the chamber as I still see no indication oil/coolant cross contamination

Thoughts??

[Slovik]

How do you know it's oil smoke, with a 71 degree thermostat you might be running very rich if the car is actually running too cool. If the car is OBD2 there are a lot of diagnostic programs dirt cheap that you can run off your laptop. If it's OBD1 your options are limited but Carsoft 6.5V is also cheap and you can get real time running data including engine temperature. Also these cars are pretty hard to bleed thoroughly, that still might be your problem, try drilling a small hole 1/16" in the edge of your thermostat at 12 O'clock and then try bleeding the car nose up, you should be able to get all the air out. I run an all aluminum e36 rad on my s52 and in South Carolina heat w/ a 88 degree stat it runs just under half, about 190 degrees. Good luck.

[L8 apexr]

Smoke is blue and for sure oil being burned,also only after a throttle blip and not during like a rich condition.Did all filling of coolant with nose up,drilled the 71 degree stat prior to reinstalling it.Did seem to be much easier to acheive steady coolant no bubbles.

[Slovik]

Possible crankcase vent valve / Oil separator. oil gets sucked into the intake when the valve goes bad. Other then worn valves, rings and valve stems if the engine is high mileage or was abused this is a good possibility. Unrelated but 71 degree is too cool for street use, almost all modern engines run somewhere between 190 - 220 degrees f just over 1/4 on your gauge is about 135.

[L8 apexr]

Didn't smoke at all prior to the overheat and the head was rebuilt before I bought it,bottom end I'm not 100% sure on mileage but like I said no smoke before.
The 71 degree stat has been in there(unknown to me)since I got it and its always run right at halfway on the gauge.I'll leave it in there until this is sorted and I can obtain a higher rated stat,I'd ordered it from IE along with all the rest of the parts but like 2 out of the 3 times I've ordered from them they forget something.This time was both the fan and the stat.I live in a little town in Canada so oem only,by chance is they an oem application to get the stat I want??.

[Slovik]

The thermostat is a very common type not unique to BMW however, my recollection is that 92c is what came stock and 88c was the warm weather option, all the auto parts stores will carry it. Hope you figure out you smoking issue and that it's not too expensive to put right.

[butters]

The 71 degree stat has been in there(unknown to me)since I got it and its always run right at halfway on the gauge.

Hmm... you might consider whether your temp output is accurate?