Help with Radiator / Water Pump

[cory58]

I've been having a cooling problem since buying my E12 in 2016. It doesn't overheat quickly, but eventually does. I realized the aux cooling fan does not coming on when the temp gets high, but it does come on with the A/C. Replaced the temp switch and that didn't fix it. Jumped the switch leads and the fan came on, so I was stumped. Mike W. gave his opinion that the radiator might be partially clogged and not flowing enough water to trigger the switch.

So, I removed the radiator today and plan to take it a radiator shop for testing. I also checked my paperwork for the last thermostat, fan clutch and water pump replacement. Thermostat was done in 2015, water pump is over 20 years old and I could not find a receipt for the fan clutch. Since I'm planning to drive the car to Octoberfest in Pittsburg, I decided to replace the water pump and fan clutch "while I'm in there."

I've already run into some challenges and I'm hoping the E12 experts here can help.

1. The radiator was a big PITA to get out. Both the Haynes manual and BMW shop manual made it sound easy, but it didn't just "pull out" after the hoses, shroud and bracket were removed. I definitely messed up some fins on the radiator and AC condenser, hopefully nothing worse. For re-installation, could I unbolt the condenser and move it forward a little bit to get more room for the radiator? Any other hints?

2. Is the bolt circled in red on this picture the bottom bolt for the alternator? If so, is there also a nut behind it that I need to get to for loosening? I couldn't get a socket on that bold from above (PS pump pulley is in the way), so I'm guessing I need to get at it from the bottom, correct?

alternator mount 1-1 by cory58f5, on Flickr

3. The allen-head bolts holding the clutch flange on the water pump are almost stripped and I could not get any of them loose with the amount of torque I thought safe. Short of making sure the allen socket is as good as possible, any other advice for breaking them loose without stripping the heads? Would it be safe to heat them with a torch?

4. Any opinions on a Beck-Arnley water pump? It's the only one I've found with a metal impeller.

5. Any suggestions for an aftermarket OEM quality fan clutch? I hope to not pay $270 for a BMW part, but am only finding aftermarket versions from companies that I don't consider OE quality (MTC, Hamburg-Technic).

Thanks for taking the time to read this long post. I appreciate all advice!

Thanks, Cory

[Mike W.]

Personally if the fan clutch feels good, smooth but with resistance, I'd reuse it. That said, there is something to be said for replacing parts that may be 40 years old. I can find it somewhat cheaper, but not what I'd call a reasonable price. Another option is to use the newer fan clutch since you're already replacing the water pump. It's much less expensive, but you would need a new fan pulley, it's got a different bolt pattern, and it's not cheap, but the package price is still far under the early fan clutch and used ones may be available especially since they were used on several different BMWs into the 90's. One possible downside is you may have to figure out what belt you need, it may or may not be the same. To go with the later style you would need the pump, pulley and fan clutch.

Beck Arnley parts are usually ok, but they're just a distributor, not a manufacturer so it's a little bit of a crap shoot on their stuff. Graf, among others, does still make a metal impeller pump, they're out there you might just have to search a bit. I was a huge fan of GMB pumps but they're changed their design. I suspect they're still a good brand, but not the great pump they used to make. On any of them just make sure which one you're getting, a lot of sites show the late parts for earlier cars.

On the socket head bolts, sometimes a good whack with a hammer on the allen drive socket will help loosen them up a bit. And if it's marginal do use a socket, not one of the folding sets and make sure you stay straight on it, not at an angle.

Radiators. The recores I've seen are as good or better than new ones, but were getting awfully expensive the last I knew with fewer shops doing them between lead issues and inexpensive plastic/aluminum radiators. Another possible option if that is the case is the all aluminum one from Amazon. https://www.amazon.com/Aluminum-2-Row-D ... bmw%3A528i I haven't used it so I can't say how well it works or fits but I think Eric Q from here did put one in a car. You might ping him if you're thinking about it and see what he says.

[cory58]

Mike,

Thank you for the great info, as always. One of my usual online parts sources (maybe AutohausAZ) has a Graf water pump. I'll verify that it has a metal impeller.

I took the radiator to a local shop at lunch. After describing the symptoms, the owner was almost sure the problem is not the radiator, but he's testing it anyway. Even though the thermostat is also new, I think I should replace it too, just to be sure. Assuming the radiator is fine and knowing the new fan switch is good (I tested it in boiling water last night), could a faulty relay be causing the fan not to come on unless I jump the wires? I'm also wondering if the temp sensors on the engine might be bad and causing a false high reading on the dash, but I think that's unlikely since the needle is right in the center when driving on the highway.

Any thoughts on unbolting the AC condenser to provide more clearance to re-install the radiator?

Thanks, Cory

[Mike W.]

E12s with the A/C on are marginal when things are in good condition, so it doesn't take much if there's a problem. One more thing I should have mentioned is does your car still have the thermo reactors on it? Those add a huge additional heat load.

More info please, does it overheat at speed or in town or when? Have you ever had it boil over or how high is the gauge? Grounds can be tricky, I had an E24 I thought was always borderline on overheating. Then I ran an extra ground, #12 wire IIRC, between the body and the engine. Suddenly it settled down just a bit left of center and rarely moved. Something to look at on that is if the gauge moves any with the wipers on or turn signals, heater blower etc. If you do see movement, you have a ground issue. I'm not sure how they switched the fan off the temp switch, it may not go thru a relay at all, but it probably does for the A/C operation. You might even consider getting one of those infared temp guns to check temps, they're pretty inexpensive these days, below $15 and you can look at temps going in and coming out of the radiator as well as checking for cold spots.

Loosening the A/C condenser to remove the radiator? I guess you could, but I've always found the radiators to come out fairly easily, excepting of course the angle my back is at while leaning over. That is one more thing about the new style fan clutch, it's easy to remove the fan with the radiator in place giving you more room to pull the radiator. But you shouldn't have to very often either.

[cory58]

Mike,

Here are the symptoms: Car eventually gets hot when idling or in heavy stop/go traffic. I've never let it boil over. Revving the engine cools it down. Once it's hot, driving it in a lower gear, so the RPMs are higher, will cool it down faster and keep it at a lower temp. Temp is fine driving on the highway. Thermal reactors are long gone. The headers on the car look 40 years old.

Regardless of the water temp, the aux fan will not turn on. I replaced the temp switch in the radiator and that did not fix it. If I jump the two wires to the switch, the fan comes on. The fan also runs when the AC is on. I tested the new temp switch by putting it in a pot of water on the stove and hooking it up to a 12v battery and multi-meter. As the water heated up, I could see when the switch closed and when it opened back up as the water cooled back down. When the aux fan is running with the AC, it doesn't seem to make a difference on the water temp. Maybe the extra load from the AC cancels out the extra cooling from the aux fan.

Regarding the overheating, the radiator shop said that the radiator is fine if the car is cool on the highway and the water pump is working if the heater blows hot (it does). They thought the problem might be the thermostat or fan clutch. Since I'd already removed the radiator and brought it to them, they are checking it out.

Thanks, Cory

[cory58]

Update: Picked up the radiator from the radiator shop today. They cleaned a lot of grass out of the fins but the flow test was fine, so the car may run a little cooler but no help regarding why the aux fan will not come on when the temp gets hot.

Cory

[528i-1981]

Wow - this is a surprise to me, so I can only imagine how you're feeling! The aux temp sensor is below the outlet of the rad - is it at all possible that there is an occlusion just above the sensor? That wouldn't show up on a flow test. Can you shine a flashlight in the sensor hole and see light through the outlet, or vice versa? Is there a baffle in between the two that could have gotten gunked up? This is just a WAG.

[cory58]

Wow - this is a surprise to me, so I can only imagine how you're feeling! The aux temp sensor is below the outlet of the rad - is it at all possible that there is an occlusion just above the sensor? That wouldn't show up on a flow test. Can you shine a flashlight in the sensor hole and see light through the outlet, or vice versa? Is there a baffle in between the two that could have gotten gunked up? This is just a WAG.

Thanks for the response! I've drained the radiator from the sensor hole, so it's not totally clogged. I will take a closer look to see if there are any partial obstructions.

Cory

[Joe Boston]

the relay to the aux fan is at the fuse box, in the photo below it's the pink colored is stage 1 of the AUx fan.



the orange is for the Stage 2 (highspeed) aux fan. you can test it from here to jump the connection...
Sound like your radiator is good shape...
You might want to install a lower temperature thermostat, if you feel that he car runs on the high temp side..

[cory58]

Thank you Joe! My earlier E12 only has a single stage fan. When I jump the wires at the temp switch, the fan comes on. Could there still be a problem with the relay? I also tested the new switch in a pot of water on the stove, to make sure it works (it does).

Good idea regarding the thermostat. My plan is to get a 71 deg C or 75 deg C.

Cory

[PatinaBeforePolish]

Now I’m curious- do cars without A/C have an auxiliary fan? I thought it was for cars with A/C and only came on when using the air.

Also, have you bled and re- bled the system? The symptom of the temp dropping at higher revs sounds like a circulation issue. Or, is the motor modified beyond the headers? Maybe you just need more capacity. Adding a third row to the radiator will help, if you can find a shop to do it.

[cory58]

Now I’m curious- do cars without A/C have an auxiliary fan? I thought it was for cars with A/C and only came on when using the air.

Also, have you bled and re- bled the system? The symptom of the temp dropping at higher revs sounds like a circulation issue. Or, is the motor modified beyond the headers? Maybe you just need more capacity. Adding a third row to the radiator will help, if you can find a shop to do it.

Thank you for the response. I think all E12s have aux fans, but have never looked at one without A/C. Mine has A/C, and correct operation of the aux fan is that it turns for either of two reasons: (1) A/C on, or (2) water temp exceeds a certain threshold.

The bleed screw is corroded to the point where I could not bleed the system when I refilled after replacing the aux fan temp switch, but I did run the car and continue to top off the coolant until it stopped taking more coolant. I've also kept an eye on the coolant level since, and it has not changed. I'm replacing the thermostat cover in order to have a functioning bleed screw.

I agree that the hot running symptoms seem like a flow problem. The radiator has a clean bill of health, and I'm also replacing the water pump, thermostat and fan clutch, so hopefully that will fix the it. I think the fan not coming on exacerbates the problem, but I don't think it's the root cause. All that being said, I think there may be a different problem keeping the aux fan from coming on.

I'm definitely not an expert at this, so any advice and/or contrary opinions from the group are welcome

Cory

[528i-1981]

While we're at it - how did you test your sensor switch? Did you suspend it so just the threads were in water, or was the sensor face contacting the pan? If the latter, you might be measuring the temperature of the pan, and the sensor could switch only at a much higher temperature than spec., so in operation it never trips.

[cory58]

While we're at it - how did you test your sensor switch? Did you suspend it so just the threads were in water, or was the sensor face contacting the pan? If the latter, you might be measuring the temperature of the pan, and the sensor could switch only at a much higher temperature than spec., so in operation it never trips.

Thanks for the response! I suspended it in the water, connected to a 12v battery and multimeter. It was not touching the bottom of the pot. Good point about it working but being out of spec. I did not have a thermometer in the pot, but it was boiling pretty good before the switch closed. I should probably test it again with a thermometer in the pot.

Cory

[Joe Boston]

Cory, this is your problem..

"The bleed screw is corroded to the point where I could not bleed the system when I refilled after replacing the aux fan temp switch, but I did run the car and continue to top off the coolant until it stopped taking more coolant."

if your bleeder screw is corrected than you would have to replace the thermostat cap, and purchase new type bleeder screw. because the Bmw's create a Air pocket in the system if not blead correctly.
One you replace the cap fill your system with 50/50 mix then turn your heater on to the max heat and then turn on engine allow the circulation to begin and occasion bleed the system until no bubble..
hope this helps..