M20 over heating issue

[Shahriar35]

Hello all,

I need some advice. For a while now my temp had been increasing and or staying at around the 3 quarter mark when I'm cruising, never really over the 3 quarter mark though. So based on other's advise, I replaced the thermostat yesterday and did not flush out the coolant, rather I just let the amount that pours out normally when the thermostat is removed release. I replaced the thermostat and poured in water to see how the car would react. After it warmed up, I bled the system and now it just shoots up the red unless I hit the gas, at which point it comes back down.

So today I called Castro's to get an idea. And they believe it is NOT the water pump and it is something else. So they would have to see the vehicle to diagnose the issue.

What do you guys think it could be? The cap? A clogged radiator? Clutch fan?

Thanks
Shah

[vert_this]

is the upper and lower hoses hot when this occurs?

[Shahriar35]

is the upper and lower hoses hot when this occurs?

I didnt touch them, I can attempt to warm up the car again and go from there when I get home.

[jlevie]

At this point I'd suspect a clogged radiator first.

[Shahriar35]

At this point I'd suspect a clogged radiator first.

Is that because you think when i hit the gas, its pushing the fluids through?

[jlevie]

I think that primarily because you say that the engine runs hot "when cruising" and that you have a new thermostat. Which I take to mean at speeds above 45mph. That would mean that air flow through the radiator or the thermostat isn't the problem.

Oh yeah, when you change the radiator also replace the expansion tank, cap, fan clutch, water pump, and all hoses. They are almost certainly well past their scheduled replacement interval of 10yr/100k.

[Shahriar35]

Now where is a good place to buy a radiator from?

I usually buy it from 1800 Radiator, they tend to have good prices.

Thanks again

[roushman90]

bleed the coolant system properly.

[Shahriar35]

I have replaced my radiator ad thermostat, and bled the system. It is still over heating, whats next? I didnt drive it around, just let it sit and it would eventually go into the red.

[e30partsguy]

Check your auxiliary fan, spin it by hand to see if it turn freely, then test your fan switch, if your switch is good and fan doesn't work, replace the auxiliary fan resistor.

[Shahriar35]

ok I spun the fan, it spins by hand but stops quickly after I spin it by hand. Now how do i test the fan switch?

I also put the car in the ON position and hit the AC switch and the fan kicked on.

[fatsooo]

For greatest safety, cooling fan and thermo-switch tests should be performed with the air conditioner off, and preferably with the engine cold. The tests below simulate a warm engine by electrically bypassing the thermo-switch with a jumper wire.
Switching temperatures are given in Table c. [ATTACHED]

Remember that the radiator thermo-switch will only turn on the electric cooling fan when the coolant temperature is high enough to close the switch. If a faulty thermostat is not allowing the coolant to bypass the radiator and warm up to the switching temperature, the thermo-switch will not close and the cooling fan will not run.

NOTE-
A temperature gauge which is not indicating normal operating temperature may be an indication of a faulty (stuck open) thermostat.

In addition, the fan will not run and the engine will overheat
if a faulty thermostat or a plugged radiator will not allow hot
coolant to reach the switch. To quickly check that the thermostat is opening and that coolant is circulating through the radiator, allow a cold engine to reach operating temperature (temperature gauge needle approximately centered) and then
feel the upper radiator hose. If the hose is hot to the touch, the coolant is circulating. If the hose is not hot, either the radiator is plugged or the thermostat is not opening.
If the coolant is circulating at normal operating temperature and the auxiliary cooling fan does not run, test the fan as described below. Disconnect the radiator thermo-switch connectors and use a jumper wire with an in-line switch to bypass the thermo-switch and simulate a switch closed by warm coolant temperature. Test the fan with the ignition on.

CAUTION-
Connect and disconnect all test leads with the ignition off.

TABLE D ATTACHED on next post


WARNING-
Always keep hands and wires clear of the fan blades. The cooling fan may run at any time the ignition is on.

NOTE-
On 318i models, the thermo-switches are located on the lower left-hand (driver's side) corner of the radiator as shown in Fig. 4-21. [ATTACHED] On 325 and 325e(es) models, the thermo-switches are located on the upper left-hand side of the radiator. 325i(is) models use a single thermo-switch combining both switch functions in one housing, also located on the upper left-hand side of the radiator. See Fig. 4-22. [ATTACHED]

If the fan runs only when powered directly by the jumpered connector, the radiator thermo-switch should be replaced. Torque a new thermo-switch to a maximum torque of 15 Nm
(11 ft. lb.). Inspect the thermo-switch gasket ring whenever the switch is removed. The gasket should be replaced if it is crushed or otherwise damaged.

If the fan does not run when powered by the jumpered connector, check for voltage at the connectors. Measuring between the green/black wire and ground, there should be battery voltage (approx. 12 VDC) whenever the ignition is on. If not, check fuse no. 19 (7.5 amp) in the fuse/relay panel. If battery voltage is reaching the connector, check the high speed relay fuse no.
18 (30 amp), and the low speed relay fuse no. 3 (15 amp).

If the fan runs only at low speed, check the high-speed fan relay (position K6). If the fan runs only at high speed, check the low speed fan relay (position K1) and the low speed resistor. The resistor is mounted to the auxiliary fan housing, behind the center of the front bumper. See Fig. 4-23. [ATTACHED] Test the resistor by removing its electrical connectors and measuring its resistance. If the resistance is not approximately 6 ohms, the resistor is faulty and should be replaced.

quoted from bentley

[fatsooo]

table d

p.s.

disclaimer - I assume no responsibility if anything happens to you or your car. I'm just posting what source I'm going to be using to test my aux fan and switch and shared my resource.

[E30Gus]

You need to double check that your fan clutch is pulling enough air to cool down the rad. With a new radiator and thermostat you are only left with the pump, clutch fan, and air in the system.

[Shahriar35]

So tonight I ran the car in a sitting position only. After she warmed up, she kept rising, the fan did not activate at all. I started up the ac, which stabilized the temp. But if I turned off the ac the fan would shut down. I do not think there is any more air in the system. so its either the switch or the water pump, I really hope its not the pump....