Re: K75 Temp Light Always On

[Steveboot]

In previous posts I recounted my testing and final repair of the problem (thanks for all the help) but I hadn't gotten the opportunity to really test it. When at last I got a good ride in the temp light stayed off, until I was home sitting in the garage and decided to let her run for a bit with no cooling from the wind. Short story long, the light started flickering and I could not hear the fan.

Since that ride I have been in the process of moving homes and between getting the old house ready for sale and the new house habitable, the K has just been sitting. However, I figured the problem was most likely either the fan or the thermostat so I ordered both from Holland. With them now in hand, and my to do list for the house not so long, I figured I'd put down the paint brush and replace them both. It would be more educational to replace one at a time, but I don't want to dump the coolant twice.

The big question now is how to make this job easier? If I remember correctly removing the radiator was hindered by the tight space. Anyone have some guidance on how to do this in a straight forward manner? I was thinking pulling the fender and front wheel off first would solve the tight space issue but may be overkill. 

[Edward]

I did the same thing a few months ago. I removed the fan for a thorough cleaning, followed by a 12V spin test. Nothing about the removal process stands out in my mind as being particularly difficult.

At the time, Samco hoses were installed, but the side rubber shock mounts arrived late. Replacing those was a huge PITA with the radiator still in place after servicing the fan. I replaced all the rubber components. The thermostat was replaced after a thorough cleaning and flush. I also replaced the radiator cap, since mine was from 1987; that prompted me to address the cooling system in its entirety.

I use Engine Ice. So, as I said, it was a straightforward and easy job. Fender removal is simple. Keep in mind that it may have been easier for me because I like removing the fairing pieces. With the Samco upgrade from the original hoses, removing them was necessary.Just get into the process once you’ve ordered and gathered all the parts for a one-and-done job, rather than the two-part process I went through. Oh yeah, I also cleaned the reservoir and added the Samco overflow hose, trimmed to size.

[Laitch]

Post a photo of your Brick, Steve, and put its model in your Signature, too, so we know what you're up against.

Replacing the fan was a nut and bolt operation with the radiator removed on my naked K. Coolant drained into a clean pan for reuse, cowl removed, water hoses disconnected, fan disconnected, radiator out, and Bob's your uncle. It could get slightly tedious with a full fairing.

Is it a coolant temperature sensor, or is it a thermostat you're installing?

[Steveboot]

I previously replaced the temperature sensor, which I remember was tough to get to. This time I'm replacing the fan and the thermostat.

After thinking it over I am going to do it in steps. First I'll replace the fan and see if it does the job. Then, if it doesn't I'll move on to the thermostat.

[Edward]

What you are about to do is very simple. Thermostats are inexpensive, so replace yours even if you think it is working properly. They do not last forever. The radiator cap is another key part of the system that is affected by age. Replace that while you are at it.

[Laitch]

Thermostats are inexpensive . . .

. . . unless they are Brick thermostats. They run from 70 to 100 USD. The thermostat is a durable part of a Brick's system. Mine has almost 100K miles because the coolant is changed regularly and the Brick is ridden often. If it's working, leave it alone. If it is a suspect for overheating, test it by placing it in a pan with water coming to a boil when it is closed and verify it has the correct opening temperature. If you remove it for testing, don't damage the perimeter gasket; replacement gaskets aren't common. If it's damage, you'll need to roll your own.

If Edward has a cheaper thermostat that has been working for him, perhaps he'll post the make and model of it in this thread.

Your Brick's fan is likely to have a corroded fan shaft, failed fan motor or corroded connector. Please keep us updated.

[Edward]

Thermostat716EDL   Radiator Thermostat - BMW K Bikes; 17 11 1 460 716 / EnDuraLast 1   $39.99
TEMPSENS-K197   Water & Coolant Temperature Sensor - BMW K75, K100; 61 31 1 459 197 / FAE 1   $39.99
TH-ORing718   Thermostat ORing - BMW K Bike; 17 11 1 460 718 / EnDuraLast 1  $4.00
 
    Subtotal:   $83.98
    Tax:   $0.00
    Shipping & Handling Cost:   $8.26
    Grand Total:   $92.24


pushing 200,000 miles.

[Laitch]

pushing 200,000 miles.

pushing that on the thermostat, the sensor or both?

For anybody who is interested, Edward's Thermostat716EDL is available at Euro Motoelectrics. The o-ring on the thermostat cover is included by EME at no charge right now

[Edward]

The thermostat crapped out on the way home from the MOA Vermont rally. I changed the sensor while everything was torn apart. The radiator cap needed to be replaced as well. There’s nothing like having hot engine coolant soak your leg while stuck in New York traffic.

[Laitch]

There’s nothing like having hot engine coolant soak your leg while stuck in New York traffic.

Medieval!

[Steveboot]

Getting everything apart was straightforward. Replacing the thermostat and fan was straight forward. Reinstalling the radiator is another story.

The Spal fan motor body contacts the air intake so that I can't get the mounting screw anywhere near where it needs to be. The rubbers are intact and the little hooked feet of the radiator slot onto them but the radiator/fan assembly can't rotate into place.

I hadn't read that this was a problem with Spal replacement, and this new one comes with the correct mounting plate so that it bolts right up. As a matter of fact, I'm pretty sure some folks commented that the Spal fan took up less room so installation should be easier. Comparing it to my Bosch fan it looks like the motor casing is deeper, but it is also a much shorter diameter. I think the Bosch would have just cleared the intake where the Spal being wider bumps into it.

Most things like this, for me, tend to be operator error; hoping that is the case now.

Edit: Decided it was easy enough to test the theory by removing the SPAL and reinstalling the Bosch. Voila, the Bosch slots in like it was made to! So either there is some trick to installing the radiator with the SPAL or it just doesn't fit.

Anyone run into this or have an idea on where I'm going wrong?

[Laitch]

Maybe you should flip the mounting plate then mount the fan on the other side, if that is possible.

Other approaches can be found on this informative page created by forum member frankenduck.

[Steveboot]

Good writeup. I'd read that before and I believe it was the first I'd read about the SPAL fan. The fan I have looks similar and came with the mounting bracket installed, but the fan has a different part number.

I'm not sure I understand what you mean by flipping the bracket and mounting it on the other side. If that means mounting it to the front it would be pulling air the wrong way and (probably) it would interfere with the cowling.

Whatever solution is it will be constrained by the existing radiator mounting points and the hoses.

I've e-mailed K Parts Holland hoping that since this was their design and it has been working they can politely tell me what an idiot I am and how to fix it (the fan, not the idiot part).

[Laitch]

I'm not sure I understand what you mean by flipping the bracket and mounting it on the other side. If that means mounting it to the front it would be pulling air the wrong way and (probably) it would interfere with the cowling.

That isn't what I meant. I meant like this. ↓

[Steveboot]

I should have realized it just by looking at your photo, but I removed the bracket and traced it both in the normal configuration and reversed. The result is about a half an inch offset. that doesn't look like it would help. However, that offset would mean the top bolt holes wouldn't line up anymore.

K Parts Holland got back to me and said they'll research it.

Oh, and I boiled the old thermostat and it opened, very slowly. So slowly that I couldn't tell at what point it started. But at 212 degs it was fully open.

And, I noticed a small rubber gasket (not the cover plate gasket) that was flat on one side. Not sure if that could have been interfering with the correct operation.

[Laitch]

Photos would be likely to clarify your description. This is an OEM Brick thermostat.

[Laitch]

I should have realized it just by looking at your photo, but I removed the bracket and traced it both in the normal configuration and reversed. The result is about a half an inch offset. that doesn't look like it would help. However, that offset would mean the top bolt holes wouldn't line up anymore..

KpartsHolland website photo.


The mounting plate flopped.


What a typical plate/fan installation looks like before it's mounted on the radiator.

[Laitch]

Here's an almost useful photo of Kpart's set up. Just turn it over then bolt it on.  The electrical cord and connection is on the engine side of the assembly, not the radiator side.

[Steveboot]

Well, a success and a failure.

I was finally able to get the new fan/radiator installed. The fan housing is hard against the intake, but it is in there.

However, when I was bringing the bike up to temperature (in the garage) I developed a coolant leak. It didn't occur until I pretty much was at running temperature, but once it started it got worse. It is coming from the thermostat cover (and maybe from the lower hose, but that may also be the dripping from the thermostat). Tried to tighten the bolts just a bit and it got a little worse (but the temperature/pressure was also getting higher). Loosened them a bit and it went back to a steady drip. And if I loosened a bit more it became a stream.

Not sure what the torque spec is for those cover bolts because the manual doesn't say. I'd used 9 NM similar to the drain plug, but I probably should have used 7 NM like the water pump housing. It doesn't sound like much of a difference, but it may be enough. I'll get another gasket and find out what the actual torque should be and give it another go.

BTW, I couldn't tell if the fan was running or not. The thermometer dipstick was at 80 degs C, and while I know that is not the crankcase temperature, I'm hoping it is a relative proxy. When I was riding before, that gauge read about 80 when it was warmed up, and the temperature light started flickering around 85 or so.

[Steveboot]

K75 thermostat.jpg (768.78 kB . 571x428 - viewed 18 times)

This picture came from an old post on this site. To my eyes it seems to show the gasket up against the posts and not stretched into the groove around the edge of the cap. I'm not sure how my old one was installed, but the manual made it sound like it should be in the groove, which is how I did it.

[Laitch]

It's clear the cap bolts have been over-torqued. The torque spec for the cap-to-housing bolts is 3.0±0.45Nm.

Part of the installation problem also could involve O-ring rubber type and sometimes, the finesse involved when inserting the thermostat. Here is a relevant post with one rider's experience. These and many other torque specs for the 2V Bricks are found in the abridged BMW K75/K100 shop manual downloadable from the Technical Directory here.

The relevant temperature activation numbers can also be found there, and the ones relevant to this thread are below.