M50B30(NV) Overheating issues

[MrSnake]

Hi All,

I'm having some issues with my M50b30(NV) overheating. Just a bit of background I bought the engine in a running E36 that drove all the way home and then I stripped it to do the rotating assembly swap and drop it into my e30.


The head has been skimmed and tested along with a new head gasket.
New water pump
New thermostat x2
New Rad
The only thing that is out of the ordinary is the deletion of the heater matrix. Here is how I have everything plumbed up:




The car is running a standalone so I can see the exact engine temps. I also know the ECU is calibrated accurately, I've tested the sensors resistance at various temps from 80°C to -10°C and it matches up.

If I have the thermostat installed the car climbs to temp and starts to overheat even with the electric fan on. The fan really is moving lots of air as its very windy in the engine bay and you can feel the hot air blowing out the back of the rad.

With the thermostat removed it will idle at 93°C. The fan kicks in and cools it back down to 89/90 °C and it will sit like that without issue. So! I decided to take it for a drive and heat soak it a bit. Unfortunately, even with the added wind from driving along it just gets hotter and hotter = 100+ until I had to kill the engine.

With the stat out, the rad is hot on both sides and I’ve blead the system countless times using the blead nipple on the rad so I highly doubt it is air in the system.

So i guess my question is where do i start!? I have even put the thermostats in the oven to make sure they open at 90 and they do so it's not a faulty stat. Sorry for such a long post i just wanted to be very clear so i don't end up going round in circles.

[Northern]

So just to be clear, mid 90's up to 100 is normal with the stock tstat after the whole system is saturated. On cooler days I'll hover around 96 and on hotter days I'll see 100.
I assume you're above 100 from what you said though.

This engine/chassis combo is notoriously hard to bleed, which is why so many people say to drill a 1/8" hole at the top of the tstat.
If the car doesn't have the front end raised, the rad is not the highest point of the system.

[ForcedFirebird]

Don't be concerned with the heater hoses, we block them off completely in the race cars and just send the port on the back of the timing cover to expansion tanks.

The radiator is not the highest point in the system, the expansion tank cap is - unless you are using an m42 radiator. I have had nothing but issues with m42 rads in swapped cars, and any of them that we work on get converted back to the m20 rad. When using m42, the cap is actually lower than the highest cooling passage in the engine, so it will always spit coolant until the level meets the cap, and an air pocket will be created. This seems to work ok for light street duty.

As Northern said, they naturally run at 96-100° - in fact the e30 aux fan thermal switch is 99° for high speed. Anything over 104° is cause for alarm. We've had a couple cars over the years that reached ~120° for a few laps after a hose/rad failure, brought it in and cooled, then went out and finished 14hr races (e36's with s50/2's). Now, I wouldn't recommend letting it get that high, just sharing experience.

[MrSnake]

Ah cool ok,

Well i'm running a standard E36 rad and tbh i just started to panic when it got to 95/100 so i was just shutting it down.

For now i will leave the stat out, get the front end up in the air and double check the system is blead. Then i'll drive it around some more and see how warm it starts to get now i know what the expected parameters are.

Give me a few days and i'll come back with my findings. Its a track build that's going for paint on tuesday so it's got no windows lol so i have to wait for it to stop raining.

Thanks for your help.

[MrSnake]

So i've been trying to remember where the hell i posted this thread and i've only just found it.

Got the thermostat back in and the car idles at 103 / 104 degs

[128keaton]

So i've been trying to remember where the hell i posted this thread and i've only just found it.

Got the thermostat back in and the car idles at 103 / 104 degs

Congratulations. I had to replace the t-stat twice (breaking TWO bolts in the head in the process) to get it to finally open and stop overheating. Glad yours was rectified