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K1100RS overhets and "everything" is new/changed o
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
Posts: 26
Location: Norway

PostPosted: Sun Sep 03, 2023 10:59 am    Post subject: K1100RS overhets and "everything" is new/changed o Reply with quote

I bought a nice looking clean original low milage -96 RS some time a go. Got it cheap because it was overheating.

Symtoms:
Temp raises stedy up towards red on temp instrument, no fan kicks in. Happens both standing still or driving in cold weather. Did som small tests check temp sensor, boiling termostat, check that water pump was operating etc and measurements without finding it out. Also tok a compression test of both cylinders and bottom/top and CO2 test of the coolant with nothing wrong.

The engine was going in for a full tune anyway so I was thinking that best would be to just get the block/engine up and running perfect and find the fault after when I knew the short block was 100%. Told the engine builder about the problem so he could give it an extra scrutiny regarding cracks or pressure problems.
Got it back and everything was averhault or changed and looking good. No issues found on the engine.
Reassembled and problems was still there...

Now I and a few other twist our heads to try and figure out what the problem are.
This is what is tested and changed again after the rebuild:

-New air filter
-Pressure test cylinders: Ok
-combustion leak check bottom part: OK
-combustion leak check top: OK
-CO2 testing coolant again: OK
-Changed fan sensor switch located on engine under radiator: No change, fan still not turns on.
-IR sensor different parts of engine to confirm that it do overheat and not just a gauge problem: Yes the overtemp is real. 115degrees on radiator and no fan turns on and overheat.
-Short the sensor under the radiator: Fan starts
-Remove fan rele and test it with power supply/multimeter: All OK.
-short fan rele base and fan turns on.
-Changed to new injectors: No change
-Changed termostat with new one: No change.
-Removed termostat: No change. Used longer time to heat up, but still overheats even when driving (some say removing the termostat the brick engines will never overheat...
-Change ECU: No change (it was flodding the engine and did not start after engine rebuild. Reasen was tha ECU somehow had let out the smoke during the build and needed to be changed.
-Opened in to colant impeller to check that the new impeller (new metal) was tighten correctly: OK
-Checked again and expelled all air in colant using vacum.
-Radiator starts to be hot in the top first and spread downwards and whole is getting hotter. When radiator was out I flow tested it and showed no evidence of restrictions.

We kind of exhausted all options.
Still can not figure why fan do not turn on when it overhats. But it should not come to that point anyway. Så the main problem we don't think is related to the fan but the fact that the system overhets somhow. But also still strange that the fan works but do not turn on Confused Crying or Very sad
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
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Location: Norway

PostPosted: Sun Sep 03, 2023 11:02 am    Post subject: Reply with quote

And to test more regarding the fan and gauge:
Where do I find how the temperature gauge is connected?
I can not find it in any wiring diagrams?

Where is it connected to?
I guess it is the smalest sensor with blue cap that is located on the coolent pump housing...
Any tips to disconnect on the sensor side and manipulate to see if the instrument gives input? (I did think a variable resistor 190-2000ohm between chasis and disconnected wire would work, but no luck making the gauge move during testing).
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Grunter
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Joined: 30 Sep 2015
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PostPosted: Sun Sep 03, 2023 11:42 am    Post subject: Reply with quote

For the increase in capacity and power I have always found the K1100 to have too small a radiator it is little large than a K75. My previous K11 used to overheat at the slightest excuse until I found the thermostat had failed, BMW thermostats fail 'shut' whereas most fail wide open.

Try running it without the thermostat in place and see if the result is the same. If so you should try elsewhere with the possibility that there is a blockage somewhere in the coolant circuit.

The radiator has the narrowest passages and a couple of them blocked will affect the cooling very quickly

Try reverse flushing to see if this clears out and lumps or just plain sludge. There is an outside chance that one of the coolant hoses has partially collapsed so it may be worth-while in the long run to remove them all and if need be clean them out manually
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
Posts: 26
Location: Norway

PostPosted: Sun Sep 03, 2023 3:07 pm    Post subject: Reply with quote

thermostats are both boiled and checked. New one fitted and tested and run also with no termostat. All resulting in overheat.

Flushed all hoses with guarden hose and looked OK. But that was after they have been laying on the shelf and dried up while the engine was at rebuild. Maybe innerline has loosened and swelled up by the coolant in place. I did order the silicone hose set along with other components from BSKspeed. Maybe fit that as next step. Thanks.

I did consider also new radiator. But with the BSK at €550 my thought was to run my original since I flushed it and water was gushing trough. It gets even hot downwoards as normal also when it heats up. Think it is a smal chanse that this is the issue for the current problem. But for sure is on the buy list when the engine is run in and see how it runs on the temperature…
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Grunter
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PostPosted: Sun Sep 03, 2023 4:11 pm    Post subject: Used radiator Reply with quote

If you have done all those things I think it will be down to some blockage in the radiator. If you can get a good one on loan and do a comparison.

If there does appear to be a fault in the radiator, there is a company in UK that sell used radiators which are guaranteed for 6 months and if there is a problem they will either replace with another or refund your money. The price asked is £130 or £108 less UK Tax. ( Aprox 1,456 Norwegian Krone). Contact Motorworks on Telephone (UK) (0044) 1484 353600.

Look at their website. https://motorworks.co.uk
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
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Location: Norway

PostPosted: Wed Sep 06, 2023 8:19 pm    Post subject: Reply with quote

Motorworks has been my go-to supplier for several years Very Happy

Did some more today:

-Checked all hoses, and they look good - no collapsed inside or restrictions. But did change them with a new silicon set I had.
-Discovered that the fan did not work every time when the cable out of the sensor switch was in its natural direction. Changed the sensor and now working every time blowing it with hot air.
-Temp sensor removed and heated with airgun and IR checked temp agains indicated. And it works/indicates as it should.
-Boroscoped radiator and flush tested it-looks normal and nothing found. But borrowed the radiator from my K100 and fitted that one.
-Boroscoped as much as I could in to the openings that was exposed during hoses, waterpump front plate and temp switch fixture was removed.

AND: Yes, still same overheat problem Confused

I have checked most things the Clymer suggests:
-Low coolant level: Nope
-Faulty water pump or thermostat: Nope
-Improper spark plug heat range: Most likely not, new originals fitted after rebuild.
-Engine oil level low: Nope, straight on the spot/mid glass when on center stand.
-Improper ignition timing (faulty components in system) - maybe, but eng runs fine and strong.


Only things I can think of now:
-Maybe improper ignition: I can try to fit a wide band sensor/instrument I have and measure where the mixture sits.
-There is some blockage internal of the engine: But there is no external hot spots when meassure with a IR sensor different places on the block/engine. And why would it raise since it flows OK trough the radiator and should therefor be cooled of Question
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Flying Duck
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Joined: 27 Jan 2005
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Location: Bumf***, WA

PostPosted: Wed Sep 06, 2023 10:38 pm    Post subject: Reply with quote

The temp sensor on the bottom of the water pump does not impact operation AT ALL. It only feeds the temp gauge.

The Motronic ECU reads the temp of the coolant coming off of the cylinder head's exit pipe behind the left lower corner of the radiator. That's the temp sensor that matters the most. (There's also an air intake temp sensor but the coolant temp matters more.)

Based upon the exit coolant temp (engine temp) the Motronic controls ignition, mixture, etc...

The Motronic also turns on the radiator fan by grounding the fan relay (blue/yellow wire) when the coolant temp gets to 105C (221F.)

Here's the ohms for various temps on a 94+ K1100:


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Last edited by Flying Duck on Wed Sep 06, 2023 10:57 pm; edited 2 times in total
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Flying Duck
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PostPosted: Wed Sep 06, 2023 10:52 pm    Post subject: Reply with quote

Here are the BMW wiring diagrams for a 94+ K1100 with English notation that I added:

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/kwiring/K1100RS.94on/K1100RS.94on.Wiring.SLP.V2.5.pdf
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
Posts: 26
Location: Norway

PostPosted: Fri Sep 08, 2023 5:14 pm    Post subject: Reply with quote

Thx, did have the other version of this spread sheet.

And it was the ECU temp sensor that was faulty at times. And is now changed with a good one. But still overheats.

Since fan now work as it should I'm moving forward to the main issue.

Engine needs to be propper run in as it should instead of just search for the fault with heat cycles. And since fan now is 100% it was time to som run in passes.

It was 18C air temp and if I run over 30km/h the speed was enough to keep temp at normal. Driving under 30km/h the fan was turning on and run all the time to keep temp at normal.
And at stand still the fan would run and temp go one bar up over normal. Don't have the meassurments her, but think that was about 95+degrees C.

For now I guess I just would fit the braud lambda and instrument to make sure its not running lean, maybe fit the new tuning injectors if it is marginal. And then do the run in period of 20 mil before I do any more investigation...
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Grunter
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Joined: 30 Sep 2015
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PostPosted: Fri Sep 08, 2023 6:45 pm    Post subject: Reply with quote

As I understand it, Norway has the most vigorous speed restrictions of all the countries in Europe with the max allowed anywhere is 60 on dual carriageway roads separated by a central barrier and I don't think there are many of those. A K1100 is a bike that like lots of high speed miles which sort of restricts you ability.
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
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Location: Norway

PostPosted: Tue Sep 12, 2023 6:02 pm    Post subject: Reply with quote

Many Interstates has 70 miles/hr. But they are booooring. Norway have one of the most beautiful and curvy roads almost everywhere outside the Interstates If I may say so.

Making a tuned K1100 one of the realy nice rides to use for a 2-4 hour late trip to wind down after work Wink

Maybe a GS would be better, but not for that price. And old cheap reliable riding bikes is scarce her. Only one I feel beats the K1100 on that part is the K100, and I have a RT and LT of that also Cool Making this K1100 more towards lokal use and nice looking ride Very Happy
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Scott_Anderson
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PostPosted: Fri Sep 15, 2023 3:28 am    Post subject: Reply with quote

When you say you installed a radiator off of a k100, by chance did you notice how thick it was.
The standard k1100 radiator has only 2 cross cores. Some k100 radiators had 3 cross cores for more heat rejection.
The 3 core radiator will fit the k1100, however you have to modify the stock cooling fan a little bit, or change it out for the "Spal" style fan that fits much better.
Check out Drake's link:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fans/fans.htm

Another thought, when you swapped the k100 radiator, did you use the thermostat that was in it?

You say you tested and replaced the thermostat, did you get BMW oem or something else. Reason I ask, the stock t-stat has a close off flange that closes the radiator bypass line when the t-stat opens for water flow through the radiator. Not all thermostats have that extra flange for the bypass close off function.
Maybe a previous owner changed the thermostat and didn't get the correct one installed. That could lead to an overheat condition as not all water would flow through the radiator for cooling. Even with the thermostat totally removed you will flow water through the bypass(path of least resistance) and the engine will get hot and possibly overheat.
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1995 K1100LT 0302044
1997 R1100RT ZC62149
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Jan E-28
Brick Rider


Joined: 18 Jun 2018
Posts: 26
Location: Norway

PostPosted: Sun Sep 17, 2023 2:52 pm    Post subject: Reply with quote

Have to check if it was the 2 or 3 core. Believe it was 3 core, since the K1100 had the noticeable thinner core then the side pods. Where on the K100 the core was just about as thick as the side pods.
Fan was not fitted since normally there would be no need for the fan at all when everything os OK.
It was the Motorworks one:
https://www.motorworks.co.uk/coolant-thermostat-coa60716-1.html

The old removed looked alike the new. But looked a bit different then the picture in the link. It was exposed two springs and looked like this:
[img]https://photos.app.goo.gl/o5kPBv5RBvSCzCWC8[/img]
https://photos.app.goo.gl/o5kPBv5RBvSCzCWC8

And did notice that when installed I thought it was odd that it was quite an opening to flow trought the radiator also when it was cold. But about 99% sure it had a design that would close of the cold bleed opening/hose when hot. But I'll check again. Thanks.
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Scott_Anderson
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PostPosted: Sun Sep 17, 2023 4:51 pm    Post subject: Reply with quote

Unless BMW changed the thermostat design, which I doubt, this is what mine look like. 17 11 1 460 716

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1995 K1100LT 0302044
1997 R1100RT ZC62149
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
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Grunter
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Joined: 30 Sep 2015
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PostPosted: Mon Sep 18, 2023 1:41 pm    Post subject: Reply with quote

Scott_Anderson wrote:
Unless BMW changed the thermostat design, which I doubt, this is what mine look like. 17 11 1 460 716


There are some aftermarket 'stats around and I have one on my K1100 and it works just fine, The actual marked lifting temp is a couple of degrees lower that the failed on I took off the bike. It was probably an original (stamped BMW, the new one isn't) so after 37 years it was probably due a change anyway.
It may be worth checking the fully open temp marked on the 'stat. Too high and it ill make the temp gauge read incorrectly.
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Jan E-28
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Joined: 18 Jun 2018
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PostPosted: Thu Oct 26, 2023 7:30 pm    Post subject: Reply with quote

I did use the k1100 termostat on the K100 radiator (Yes the K100 radiator is thicker with 3 cores.

Boiled all the termostats now again and I see that the K100 looks just like the others, exept that it opens a bit more up then the old and new for the K1100.

Fitted the K100 termostat also and now the bike at least do not go towards red. Before standing still where the fan was not enough to keep it cool it now gets cooler when fan turnes on. But the air temperatur was just 10C (50F)

So the K100 radiator with the K100 termostat keeps the heat in bay. At least when weather is cold. But there is still a problem. My two k100 never even turns on the fan...

K100 got the K1100 radiator mounted with the termostat that did not open as much and it runs just fine as it did before. And standing idle inside in 22C hangar the fan not even turns on.
IR measure on the water pump during the same course and the K1100 runs about 5C (40F) hotter then the K100. (And that is when the K100 is fitted with the smaller k1100 radiator and termostat that did not open as much).


But on thing I did notice:
Filling up coolent on the K1100 in the end the filler "gurgels" and spitting when bubbles comes up and need to "milk" the hoses to expell all air. And need to pour slow.
On the K100 it just gulps down the coolent with no issue. No need to "milk" the hoses to expell all air...

Beginning to think that there actually are a blockage somewhere. Even tho everything external is new/changed and engine gets even temp outside measuring it with IR.

Top on my board now is that there is some sort of obstruction in a coolent channel inside the engine that the engine rebuilder was not able to see or find during tuning :hmm
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Flying Duck
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PostPosted: Sat Oct 28, 2023 1:18 pm    Post subject: Reply with quote

To reduce the K1100 gurgle you can undo the mounting nuts for the filler and hold it higher.
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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
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91 K1
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Jan E-28
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Joined: 18 Jun 2018
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PostPosted: Sun Oct 29, 2023 4:37 am    Post subject: Reply with quote

I did and stretched ut up. Even tried to use a long necked funnel all the way down to the radiator with no help.
Filling the k100 it was still attached with screews and worked fine.
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Al.
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PostPosted: Thu Jan 04, 2024 8:03 am    Post subject: Reply with quote

I'm very late to the party, probably solved by now.

If the fan is not coming on.......
I didn't read through all the posts.
I had the problem had most of stripping done and came
to socket on fan cable. It was a good shade of green inside.
I think if I had gone there first it might have been the answer.

Is the fan working directly off battery??

Did you test cable continuity.
Had that problem with ignition switch cable,
took a while to figure it.

Apologies if I'm covering already answered....

To me it's electric/electronic.
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Jan E-28
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PostPosted: Fri Jan 05, 2024 5:13 am    Post subject: Reply with quote

Fan is working fine but problem is still there Crying or Very sad
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