Overheating exhausted all avenues m20 2.5

[Nickerz]

Recently had head rebuilt pressure tested and refitted. Having trouble with gauge creating up to red. Have tried bleeding with front jacked up heater on new thermostat new water pump. Bottom hose on rad always stays cold but when massarging evently gets warm. Have tried this process multiple times. Vents get hot no air coming out of bleed. Nut checked on back of cluster to rule false temp reading. Gauge just won’t sit at half way. Running out of ideas

[mark_i]

what engine do you have...? M40 have an additional bleed screw on the stat housing

[mark_i]

oops! just seen title, its an M20.
Have you checked the cap on the expansion bottle? should have a yellow insert

[Nickerz]

Will check insert but I’ve bedn running it up with cap

[Nickerz]

Will check insert but I’ve bedn running it up with cap

[Steve]

Have you changed the rad? Had the same problem did water pump etc.. but kept getting hot, rad looked good but really wasn’t.

[Nickerz]

Should of said new rad

[mark_i]

also check that the 10mm diameter tubing from expansion tank to top of radiator is clear

[arrisbmw]

if the bottom hose is cold , points to water not circulating through the whole system .
could be an air lock. brian moore got a post on here on how to bleed sys.

or try removing the thermostat completely. then the two main hoses top and bottom should be about the same temp with the engine running, it won,t get up to temperature at all, won,t be stable, its not a long time fix as the car won,t get up to normal operating temp as its designed to,
i think the stats on these cars need to be original fitment. not a patent part. someone oh here will know better
than me with more experience.

[Brianmoooore]

i think the stats on these cars need to be original fitment. not a patent part. someone oh here will know better
than me with more experience.

There was actually a design weakness with the OE stats. fitted to E30s by BMW, and to many later models. This may have been addressed by now, but I (and my wallet) prefer a good quality aftermarket item.

The airlock that plagues E30 M20 cooling systems after a refill, is best sorted by filling the coolant bottle to the brim, then removing the top heater hose from the matrix stub pipe at the engine bulkhead, and refitting it while coolant is flowing from both the stub and the hose.
Flow can be encouraged by pulling in the overflow hose from the inner wing, placing the end of it in your mouth, placing your hand flat over the top of the bottle neck, and blowing.
mark_i 's post about the 10mm rad. to bottle hose is important as well, including checking the stub pipe into the bottle.