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Author Topic: Running too cold?  (Read 9935 times)

Offline F14CRAZY

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Running too cold?
« on: October 14, 2015, 07:32:11 PM »
Judging by the VDO temp gauge, my bike normally runs between 165f and 170f.

Being that winter is coming I've riding in temps in the 40s and 50s. Judging by the gauge, it runs at 145-155f. Keep in mind that I'm commuting around 60 miles at 75-80 mph so there's a lot of flow through the radiator and over the engine.

Should I be concerned at all about it running cooler? I think my thermostat is fine since it stays around 170f in the summer (till it sits in traffic) and gets up to temperature (albeit gradually...from what I've read all K's take a while...much longer than my Subaru). May be a drop of a couple MPG lately but it's hard to tell even with Fuelly. It's not like the system is running a cabin heater but should I be concerned as far as the oil not getting hot enough for proper lubrication? I switched to 10w40 from 20w50 today for better cold starts.

I had an old Ford Explorer that would never get up to normal temperature in winter according to the gauge and heater performance (and grabbing the upper radiator hose). New 195f thermostat didn't change anything. I ended up blocking the entire radiator with cardboard which got it into the normal zone and got the heater to work well.

Should I consider blocking some of the K's radiator?

Thanks guys

 
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  • Grand Rapids, MI
  • '87 K75C
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Offline Scott_

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Re: Running too cold?
« Reply #1 on: October 14, 2015, 10:00:43 PM »
I'd suggest, no, let it be.
I've noticed mine also is running cooler with the lower morning temps, and that's ok.
As far as the oil goes, 20w-50 is good down to around 15deg F.  Colder than what I'm going to ride at anyway......I park them at 30, as I have had fork seals start leaking below that temperature.
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Offline F14CRAZY

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Re: Running too cold?
« Reply #2 on: October 28, 2015, 11:30:52 AM »
The cold and the rain this morning kept the bike from getting much above the 100f mark. I've duct taped the upper half or so of the radiator. Will see if that gets the temperature up a bit
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  • Grand Rapids, MI
  • '87 K75C
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Offline Laitch

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Re: Running too cold?
« Reply #3 on: October 28, 2015, 12:22:05 PM »
Verifying the accuracy of your bike's temperature gauge and sending unit might be helpful to prevent inadvertent overheating.
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Offline F14CRAZY

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Re: Running too cold?
« Reply #4 on: October 28, 2015, 12:42:05 PM »
Quote from: Laitch on October 28, 2015, 12:22:05 PM
Verifying the accuracy of your bike's temperature gauge and sending unit might be helpful to prevent inadvertent overheating.

Well if it helps my sender is new this season and the VDO gauge should be good. In warm weather it cruises between 165f (guesstimating by the gauge markings) and 170f (which is marked). When my fan wasn't working the hot light came on around where it should be (I forgot what the spec is for the hot light). Fan (now working) comes on about when it should too.

A legit concern Laitch but I think the gauge's accuracy is pretty good.

It's a little frustrating having a gauge with markings at 100, 170, 210, and 230f. It's vague in my opinion. I'd rather have something digital or with different markings
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  • Grand Rapids, MI
  • '87 K75C
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Offline Laitch

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Re: Running too cold?
« Reply #5 on: October 28, 2015, 12:55:03 PM »
I'm at the other end of the concern spectrum. I'd rather not have a lot of dial information. It would interfere with my ride. :hehehe Well, it sure seems odd that at a temperature as warm as 40ºF you'd need to block the radiator. I'd guess you're sure the coolant ratio is ok. Interesting.
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Offline The Mighty Gryphon

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Re: Running too cold?
« Reply #6 on: October 28, 2015, 01:01:34 PM »
You mention a VDO temperature gauge.  Are you using it with the BMW sending unit?   I didn't think the VDO sender fit properly in the sending unit port on the water pump because of it's extended probe..  If you are using the the BMW sender, I would double check the temperature/resistance curves to see if you are reading the correct temperature.  I seem to recall that the BMW/Bosch sender has a slightly different curve vs. the VDO.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Laitch

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Re: Running too cold?
« Reply #7 on: October 28, 2015, 01:55:18 PM »
I'd still compare the gauge with another sensor/thermometer stuck into the coolant flow somewhere, and then there's that thermostat that was working ok in the summer, but it could have failed.

The duct tape is a picturesque idea though and now it comes in party colors. The radiator fins might become a little gooey—a small price to pay.
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Offline kioolt

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Re: Running too cold?
« Reply #8 on: October 28, 2015, 01:58:40 PM »
I'm surprised that no one has mentioned that the problem might be the coolant thermostat.
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Offline Laitch

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Re: Running too cold?
« Reply #9 on: October 28, 2015, 02:02:19 PM »
 I'm going to have some apple pie. :lets-eat:

Ah! That's more like it!
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  • Along the Ridley in Vermont.
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Offline F14CRAZY

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Re: Running too cold?
« Reply #10 on: October 28, 2015, 02:42:18 PM »
Quote from: Laitch on October 28, 2015, 01:55:18 PM
I'd still compare the gauge with another sensor/thermometer stuck into the coolant flow somewhere, and then there's that thermostat that was working ok in the summer, but it could have failed.

The duct tape is a picturesque idea though and now it comes in party colors. The radiator fins might become a little gooey—a small price to pay.

lol I went with black. Could have used red to match the bike (or blue...it's cold)

On days where it's in the 60s the temp runs normally. I could remove it and test it on the stove I suppose.

Quote
You mention a VDO temperature gauge.  Are you using it with the BMW sending unit?   I didn't think the VDO sender fit properly in the sending unit port on the water pump because of it's extended probe..  If you are using the the BMW sender, I would double check the temperature/resistance curves to see if you are reading the correct temperature.  I seem to recall that the BMW/Bosch sender has a slightly different curve vs. the VDO.

Yeah, a BMW sending unit. That could be an issue
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Offline K1300S

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Re: Running too cold?
« Reply #11 on: October 28, 2015, 04:05:48 PM »
having installed vdo gauges in old bimmers, matching the range of the sender and the gauge is CRITICAL.  and a sender cannot drive multiple gauges.  I am going to guess a range mismatch is the issue here as normal operating temps for engines should be in the 180-200 range.  seeing 170 in summer would be low.  (I am new to bricks, this is based on BMW auto engines of the same vintage.  my musings may be totally out of whack.......!)

since K75's did not come with temp gauges, is there detail somewhere on how to put one in?
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Offline F14CRAZY

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Re: Running too cold?
« Reply #12 on: October 28, 2015, 06:37:36 PM »
I've figured my bike has a 165f or so thermostat. After adding the duct tape and riding back to Grand Rapids (mid 50s, rainy, 70-75 mph) I found that the temp gauge rode where it usually does in the summer:



I consider this spot to be normal operating temp. Needle is right through the 1 in 180.

My temp gauge uses a BMW sender (interchange for the '84 325i or w/e it is) screwed into the water pump housing (K's without a temp gauge have a plug here, it's right by the oil pressure sender).

Earlier this season when I was having issues with my water/oil pump leaking I inadvertently broke my sending unit. I replaced it with the one prescribed for the old 325i. They looked the same and since the gauge read operating temp to be in the same spot I didn't think anything of it.

Think I should replace my thermostat for good measure? I searched the forum and it seems one prescribed for older Toyotas interchanges and isn't $50+.

Should I hook up a mechanical temp gauge to check mine?

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  • Grand Rapids, MI
  • '87 K75C
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Offline K1300S

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Re: Running too cold?
« Reply #13 on: October 28, 2015, 07:22:04 PM »
not all bmw senders have the same range, and not all vdo gauges have the same range.

I would use the correct vdo sender for the gauge you have.

you can buy a cheap IR temp gun from the hardware store to easily check what the coolant temp is.

thanks for the hint about the plug in the waterpump housing!
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Offline The Mighty Gryphon

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Re: Running too cold?
« Reply #14 on: October 28, 2015, 09:16:43 PM »
The reason I mentioned the mismatch in my earlier post was that I installed a temperature gauge on my K75RT last winter.  I wanted to use a VDO gauge, but the extended probe on the sender looked like it wouldn't fit properly without blocking some of the coolant flow.  Spent a lot of time unsuccessfully searching for a sender without the extended probe.  Thought I could use the BMW sender with the VDO, but the curves were off so the gauge would be inaccurate.  I couldn't find anything that would work properly with the BMW sender, so I ended up using a BMW gauge as well.

Having said all that, I too, think it sounds like your thermostat is stuck open.  These bikes should have no problem holding the coolant at the proper temperature at any ambient. 
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline F14CRAZY

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Re: Running too cold?
« Reply #15 on: October 28, 2015, 09:29:32 PM »
Gryph: I was waiting for someone to post how their bike does in the cold. I'll change out the thermostat soon...likely this weekend
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  • Grand Rapids, MI
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Offline K1300S

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Re: Running too cold?
« Reply #16 on: October 28, 2015, 09:43:19 PM »
Quote from: The Mighty Gryphon on October 28, 2015, 09:16:43 PM
  Thought I could use the BMW sender with the VDO, but the curves were off so the gauge would be inaccurate.  I couldn't find anything that would work properly with the BMW sender, so I ended up using a BMW gauge as well.

shich bmw sender and gauges did you end up using?
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Offline The Mighty Gryphon

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Re: Running too cold?
« Reply #17 on: October 28, 2015, 09:54:42 PM »
I used the stock sender, harness, and gauge that are used on the K100RS.  Got them used off of eBay.  I think they are the same that are used on all the early K bikes.   As I recall, everything plugged into the existing K75RT main harness.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline K1300S

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Re: Running too cold?
« Reply #18 on: October 28, 2015, 10:46:23 PM »
thanks!
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Offline F14CRAZY

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Re: Running too cold?
« Reply #19 on: October 30, 2015, 05:39:59 PM »
I picked up a thermostat today from Advance...specified for a '98 Toyota Celica 2.2L. I brought one with me (from a spare radiator) and it's gonna work. I'll swap it out tomorrow.

Price was $10...much cheaper than the dealer. Otherwise it's $56.58 at BMWMC of Grand Rapids
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline F14CRAZY

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Re: Running too cold?
« Reply #20 on: November 02, 2015, 11:42:42 AM »
First time with the Toyota thermostat...

Ambient temp this morning was 50f. With no duct tape in front of the radiator the temp gauge read where it was in the previous pic...just before 180f. I'd say that's not bad. Counting that this 180f thermostat is working fine with the K radiator, and that my VDO temp gauge and the sender are working, I'd say the problem is fixed.

As mentioned in another thread I'll have to see how it does when its really hot out
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

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