318 cooling system questions

[snaponbob]

FIRST time to fool with an E36 4 cylinder. This is a 1996 M44 318.

Not at all confident I understand the cooling system. The 6 cylinders I have down pat as I have been working on and rebuild dozens and dozens of them over the past 7-8 years. Here is what I have seen -- the engine will warm up to what appears to be normal temps based on the temp gauge and monitoring coolant temp by looking at the data stream on a Snap-On scanner. The engine will warm up to about 190 degrees and hold that temp. The top hose is getting real hot (as it should) but the return hose stays at ambient temps (cold). The heating system is blowing hot into the passenger compartment at idle. The radiator appears to NOT be clogged.

The thermostat is 95c (203f) which is the only available choice. Given that, at 190f coolant temps, it won't open. When the engine is revved up, coolant flows into the reservoir from the orifice in its neck.

If the t-stat isn't opening and the return hose is remaining cold, how in the world can this engine NOT overheating ?!?!?!?

[Eric93se]

How about when you drive it, how are the temps, real data not the gauge?

[MadRomeo]

FIRST time to fool with an E36 4 cylinder. This is a 1996 M44 318.

Not at all confident I understand the cooling system. The 6 cylinders I have down pat as I have been working on and rebuild dozens and dozens of them over the past 7-8 years. Here is what I have seen -- the engine will warm up to what appears to be normal temps based on the temp gauge and monitoring coolant temp by looking at the data stream on a Snap-On scanner. The engine will warm up to about 190 degrees and hold that temp. The top hose is getting real hot (as it should) but the return hose stays at ambient temps (cold). The heating system is blowing hot into the passenger compartment at idle. The radiator appears to NOT be clogged.

The thermostat is 95c (203f) which is the only available choice. Given that, at 190f coolant temps, it won't open. When the engine is revved up, coolant flows into the reservoir from the orifice in its neck.

If the t-stat isn't opening and the return hose is remaining cold, how in the world can this engine NOT overheating ?!?!?!?

Your thermostat should have a bleeder on it to allow a little flow before it opens (not much though). That being said, are you positive you still have the 203 degree thermostat? Many people change theirs to lower temp ones. And it's my understanding that the thermostat should be fully open at 203 degrees. That would mean it starts opening before that. Regardless, your thermostat is opening because the upper hose gets hot. The other sign is the recirculation of coolant back to the reservoir. I imagine the M44 doesn't put out a whole lot of heat, it might not need the thermostat to open all the way to maintain operating temperature.

[snaponbob]

Going to find out. BUT, no tags!!!

[Eric93se]

Wedge a piece of wood on the gas peddle, put it at 1500rpm and see how it handles it.

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That bleeder on the thermostat is negligible, just for air. But the thermostat may be a crap brand and may open very little and slowly.

[snaponbob]

Wedge a piece of wood on the gas peddle, put it at 1500rpm and see how it handles it.

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That bleeder on the thermostat is negligible, just for air. But the thermostat may be a crap brand and may open very little and slowly.

The existing t-stat was not opening. Got a new Mahle, and all is okay. WEIRD system. A 93c t-stat, and the electric fan is programmed to start at 217 degrees !!!​ And it shuts off at 206.

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