engine and drivetrain help! radiator problem...feedback needed!

[Hugh]

So, after my engine mounts went soft and my engine fan chewed up my stock radiator, I brought the whole works into the shop to get fixed. I got a new 320i radiator (more on this later), new motor mounts, and a new ELECTRIC engine fan.

Never before has the temp gauge read above center....has always sat perfectly horizontal...now with all of this new cooling gear, the thing reads above center, and at idle, after a few minutes, climbs up into the RED....crap...I pulled over and let it cool down but it took forever...the fan IS working and pushing major air through the radiator. (I put my hand down there and felt it.)

The deal is this, the new radiator that they put in is quite a bit TALLER than the stock 02 radiator...is this normal? Also, there is no provision in this (PLASTIC) radiator for a thermo switch so currently, the fan is wired to be on all the time (ignition on obviously).

They did a beautiful install...clean and nice hardware, relay for the fan.

What can be wrong? incorrect radiator? (maybe true but wouldn't seem to make it overheat to me). bad thermostat?

help please! Thank you!!!!!

[mikem]

Or, is the fan blowing the correct direction?

[Hugh]

The fan is in front of the radiator and is blowing the air from the front, backward, through the radiator into the engine compartment...I believe this is correct?

[Napes]

There was a reason the German engineers put the fan between the rad. and the engine. This gives totally uninterupted air flow over the engine, not a flow blocked by the rad. I would suspect the rad is getting sufficient cooling, but you'd be better off with more uninterupted air flow over the engine itself. Just my thoughts. I run a NOS OEM 2002 rad, BMW coolent, 71ºC thermostat, stock 5-blade fan w/ shroud, and my car doesn't overheat in 105º-110º southern AZ summers.

Bob Napier

This w/ the A/C full on, also.

[Arizona02]

circulate thru pushing any air out. Having the front end of the car up on jack stands can help get the air to bleed out of the engine. Use a piece of paper to verify direction of air flow from rad fan.

[TobyB]

Well, the fan only matters in traffic-

I vote for the air bubbles in the heater circuit, as the

back of the head needs to 'burp' too...

I run the 320 rad in the race car, and it stays cool (ish) at 2500' and 100f exterior...

The quick test- is the rad getting really hot at the bottom?

It will at the top, but should get cooler as you work your way down.

One random bit- depending on how you wire the fan, the return

(ground) can induce error in the metering circuit. My car runs 'hotter' with the headlights and fan on, for example- it's just mediocre grounding, really, but if I'm not paying attention it can freak me out...

fwiw,

t

[Hugh]

yes...the radiator definitely gets cooler toward the bottom.

I am going to check the air in the system as this seems to be what everyone thinks. Interesting about the possible grounding issue with the sender. Thanks!

[DanOKC]

My vote is for bad thermostat.

[jwnors]

Why would the radiator stay cool at the bottom? Wouldn't that heat up when the thermostat opens and mixes with the engine water? I am having a problem where I don't believe my new thermostat is opening. It's installed correctly and I've tested it in a pan on the stove. The lower radiatior never gets warm and the lower hose on the thermostat is always cool telling me it is not opening. any ideas?

[robspeed]

So, after my engine mounts went soft and my engine fan chewed up my stock radiator, I brought the whole works into the shop to get fixed. I got a new 320i radiator (more on this later), new motor mounts, and a new ELECTRIC engine fan.

Never before has the temp gauge read above center....has always sat perfectly horizontal...now with all of this new cooling gear, the thing reads above center, and at idle, after a few minutes, climbs up into the RED....crap...I pulled over and let it cool down but it took forever...the fan IS working and pushing major air through the radiator. (I put my hand down there and felt it.)

The deal is this, the new radiator that they put in is quite a bit TALLER than the stock 02 radiator...is this normal? Also, there is no provision in this (PLASTIC) radiator for a thermo switch so currently, the fan is wired to be on all the time (ignition on obviously).

They did a beautiful install...clean and nice hardware, relay for the fan.

What can be wrong? incorrect radiator? (maybe true but wouldn't seem to make it overheat to me). bad thermostat?

help please! Thank you!!!!!

I agree with the air in the system diagnosis. you must BLEED the air out!!! open the heater valve, open the radiator, warm it up until HOT air comes out of the heater ducts, THEN rev the motor to blow out all the air. top off the rad, put cap on, live life...

[ingraham]

Check for trapped air as noted earlier.

If the coolant overheated earlier, that could have damaged the thermostat. Try another if you have it. Also, you could have cracked the head or the head gasket; that can account for the overheating.

If it overheats on the highway, you can assume the electric fan is not the problem.

If your radiator is new, it is not the problem.

Any chance the new radiator got clogged with junk dislodged from the cooling system during the repairs?

An E21 320i radiator is the same height as a 2002 radiator,about two inches wider, and uses the same bayonet cap.

An E30 318i radiator is about the same width as a 2002 radiator, about 3/4 inch taller, and has a threaded cap. Maybe that's what you have.