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  • Thermostats and your radiator

    This article is to shed some light on using a cheaper thermostat rather than the OEM PN#17 11 1 464 985 priced @ $41.58. Thanks to cal, we know there is an aftermarket Auto thermostat that is similar to the BMW unit and uses a PN of 032 121 110B. This aftermarket unit can be found for as little as $4.00 here http://rothengine.com/032121110BThermostat.aspx and there are several other China made units out there but I have found the valve ram to be considerably shorter than the OEM and despite the same 87C rating, they are slow to extend (open). One alternative to the many various china units out there is the one member "cal" referred to here http://www.ebay.com/itm/180624619490...84.m1439.l2649. Despite the advertising of this thermostat being of German origin, the plastic body is identical to the China brethren right down to the casting seems and in all the physical dimensions. The valve ram may very well be of German manufacture since it out performed the China "VIKA" $4 dollar unit in the boil test. In this photo, you see the China Vika unit on the left and the German/China Topran in the middle and my OEM on the right. The rams are responding to a 190F water temp. In like order There are several dimensional differences of the China bodies compared to the OEM. Namely, the China valve head is .024 larger in diameter and it has .019 less travel to be fully opened. Technically, the China body is slightly more restrictive in this respect but not enough to exclude the use of a China bodied thermostat. What is most interesting and the biggest difference in the China bodied units and OEM is the spring rate that holds the valve shut. The OEM requires 45 lbs of pressure from the valve ram to fully open the valve while both the China Vika and China/German Topran require only 27 lbs to maintain a fully open position. The coolant flow runs with the spring expansion, not against it so the flow would increase the pressure of the valve ram tip into the plastic radiator ram pocket as the small hole pictured here is the seat of the valve ram. I can imagine over time, its possible the extra heavy OEM sprung valve ram "may" deepen the plastic seat causing a somewhat latter valve reaction time resulting in a slightly hotter running engine. My radiator is rather new with only 4K on it so I measured the ram "seat" bottom to the bottom of the tank mouth and came up with 3.580". It would be interesting to see if anyone with a hi mileage radiator can verify that their valve ram seat is any deeper. I installed the UK sourced Topran in my 03 and a couple of test rides confirm a well functioning engine temp. What is also of interest is the radiator design is of a passive siphon type. This type is the least restrictive in flow rate but not as effective in low RPM cooling. To elaborate, take a look at this shot... Unlike an Auto radiator that forces all coolant through the cooling fin channels, these radiators allow a certain amount of hot coolant flow directly back into the engine. The above photo shows a thermo valve in a fully open condition. The hot coolant from the engine comes directly up into the bottom of the thermostat hits the underside of the valve head and has an open avenue to the outlet back to the engine as shown in the photo and it also can flow into the bottom rows of the rad "if" the valve has already opened. Im not sure why they didn't used a more conventional rad design but if it was a size and cost problem, this rad unit is perfect! As a tip on removing the thermostat, my horseshoe shaped retaining spring clip, slid back and out easy enough but be prepared to scratch off the paint that may hold it in place. I used the rubber grip end of a small hammer to whack the thermo housing inlet barb from every direction sideways until it stated to move downward slightly. as shown After it came down about 3/32, I used a long punch and taped at the brass thermostat "head" until the entire housing finally popped out of the bottom as a unit like this
    Last edited by xtriggerman; 08-12-2013, 12:04 AM.

  • #2
    Now, that's some useful sh*t! Thanks XT!

    I've been thinking about a preemptive t-stat replacement on my bike - what prompted you to dig into this?
    Rotax owners fan club member
    2003 Dakar - 139,000 miles

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    • #3
      Once again I''m so pleased to own a classic !!

      Comment


      • #4
        @Upsidedown

        you are sooo right, mate !

        Altough I will be a soon to member of the 'pull the carb' club (official initiation rite !?) - I still marvel at the maintainability of the liberally plastic clad Funduro.
        Realy ... (normally riding & maintining airhead boxers...)


        Did you see atomicalex's report 'Katherine attempts to fix a bike' -> http://f650.com/forum/showthread.php...o-fix-her-bike

        Ouch , ouch...
        I did contemplate and mediate about getting a twin spark Dakar or the like.
        But Katherine's pics look like the dungeon of doom... - not the fact that the conn rod and likely the crank is shot - but just looking at the FI GS's 'faux tank' contraption under the hood...

        Just saying.
        And: apologies to FI GS owners: not to say that the FI GS is a bad bike - this is strictly about maintenance.

        happy trails
        Jan

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        • #5
          Thanks for your comments guys. Reason for my evaluation is I overheated my bike riding it home from the used bike shop up in NH in the Boston tunnel from hell. I didn't think it should have overheated and latter found no issues with the cooling system. I love the bike and the 75mpg that its capable of puts it way ahead of any other bike I can think of for the $4500 I paid for it. But like anything mechanical, today I believe some systems are too cost compliant and as in the automotive industry, some things are simply designed to make the repair shop happy. After I saw these pics cal posted about his Venezuela melt down, I thought it would be fun to look into this. As you can see, the rad in cals bike was a bit clogged and being a passive system or direct flow for that matter, probably caused his catastrophic melt down and welding of plastic internals. In one shot you see the thermostat valve head literally welded shut. This condition resulted in virtually all the hot coolant flow to completely bypass the radiator and the fans effect way on the other side of the radiator. I would also point out that you can see the extra strong valve spring that jammed the valve head into a weld shut condition. I wonder if the lighter China spring could have reduced the chances of a valve ram malfunction and keep the valve open for flow with the far less spring resistance. Stardust, thanks for the Katherine link. I just went over it and found it most interesting. That sort of brings me to my next evaluation in the works of the engine oil system. My goal is to see if there are certain oils that do not "hold" as much air as what I am seeing. To check the oil level of any engine should not be such a guessing game and its all due to the fact that this engine pulverizes the oil with bubbles making the volume of oil in the sump a wide variable. IMO, the oil level should be checked cold and only after you start, run the engine for 10 seconds and turn it off. At that point you have normalized all the oil cavities with non bubbled oil and have the minimum oil volume in the sump. My oil level window shows no oil at this point but an oil level check per manual shows a window with only a tiny air space at the top. so just what am I measuring here..... the ability of my oil to retain air! That is sooo not right, IMO. Just old school I guess......

          Comment


          • #6
            xtriggerman
            Nice wright up! My F was running hotter than I thought it should with the fan running at highway speeds in 115 temperatures. and this is why I changed the thermostate and used the Topran supousedly from germany. I now have 11000kms with this stat and the fan is back to running normally, I can tell when the fan is running because I have a LED hooked up to it, placed in the dash. I have riden my F to Panama twice but never to Venezuela so the melted rad is someone else not me,I do remember that problem from some other reading in another thread.
            Cheers

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            • #7
              Originally posted by cal View Post
              xtriggerman
              Nice wright up! My F was running hotter than I thought it should with the fan running at highway speeds in 115 temperatures. and this is why I changed the thermostate and used the Topran supousedly from germany. I now have 11000kms with this stat and the fan is back to running normally, I can tell when the fan is running because I have a LED hooked up to it, placed in the dash. I have riden my F to Panama twice but never to Venezuela so the melted rad is someone else not me,I do remember that problem from some other reading in another thread.
              Cheers
              Thanks for steping in with some more info on the Topran. I think I will cross section the ram on the one I broke apart and my OEM to see how the rams work. There has to be a reason for the extra strong spring in the OEM and im thinking the OEM ram is harder to retract due to finer porting. And sorry for hanging that clogged rad on you, I miss understood that Venezuela post.

              Comment


              • #8
                I wonder what t-stat is used in the Bombardier DS-650 ?

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                • #9
                  +1 on the Classic comments. I'm thinking of snatching up another one or two so I have it when I wear out my ST, lets see, that ought to be in 2025. Never mind.

                  Comment


                  • #10
                    Well, no evaluation would be complete without understanding exactly how these thermostats work so here is a cross section of the brass ram assembly. The steel ram is simply forced out of the brass body by a mercury/wax compound. The waxy substance has a candle wax consistency at room temp but goes fluid when headed, expanding to push the ram or pin out through a large rubber grommet type seal. Simple enough.... but $42 bucks for BMW? Your choice.

                    Comment


                    • #11
                      Originally posted by xtriggerman View Post
                      This article is to shed some light on using a cheaper thermostat rather than the OEM PN#17 11 1 464 985 priced @ $41.58. Thanks to cal, we know there is an aftermarket Auto thermostat that is similar to the BMW unit and uses a PN of 032 121 110B. This aftermarket unit can be found for as little as $4.00 here http://rothengine.com/032121110BThermostat.aspx and there are several other China made units out there but I have found the valve ram to be considerably shorter than the OEM and despite the same 87C rating, they are slow to extend (open). One alternative to the many various china units out there is the one member "cal" referred to here http://www.ebay.com/itm/180624619490...84.m1439.l2649. Despite the advertising of this thermostat being of German origin, the plastic body is identical to the China brethren right down to the casting seems and in all the physical dimensions. The valve ram may very well be of German manufacture since it out performed the China "VIKA" $4 dollar unit in the boil test.
                      The ebay link to the German unit is no longer available so i searched on the OEM number and found this: http://www.ebay.com/itm/SEAT-LEON-TO...-/171109500900
                      Any idea if that is the same unit?

                      Also, from what i am hearing this unit opens further and helps circulate more fluid through the radiator so that it runs cooler in hot weather. Would it affect how long it takes to warm up or limit how hot it will run in cold weather?
                      2006 Dakars

                      Comment


                      • #12
                        Originally posted by Don Coyote View Post
                        The ebay link to the German unit is no longer available so i searched on the OEM number and found this: http://www.ebay.com/itm/SEAT-LEON-TO...-/171109500900
                        Any idea if that is the same unit?

                        Also, from what i am hearing this unit opens further and helps circulate more fluid through the radiator so that it runs cooler in hot weather. Would it affect how long it takes to warm up or limit how hot it will run in cold weather?
                        Can't answer your specific questions about the replacement unit but I CAN assure you that this unit will perform better than a broken or non-operational OEM unit.

                        I'd be surprised to see much performance gain with any replacement part - there just isn't the possibility of increasing the flow enough to make a real-world difference. As long as the operation temp. set point is similar, all is good.

                        Once you see how this thermostat and radiator setup works (as a diverting valve) you can understand why removing the thermostat is a BAD idea, as has been stated elsewhere This is unlike most car setups, wher you can remove a faulty thermostat as a temp fix when it has failed. Although, clearly the Seat cars are similiar!
                        Wayne - 2001 BMW F650GS Dakar - "Checkers"

                        "...The world is actually on your side..." - Ted Simon

                        Comment


                        • #13
                          Originally posted by Don Coyote View Post
                          The ebay link to the German unit is no longer available so i searched on the OEM number and found this: http://www.ebay.com/itm/SEAT-LEON-TO...-/171109500900
                          Any idea if that is the same unit?

                          Also, from what i am hearing this unit opens further and helps circulate more fluid through the radiator so that it runs cooler in hot weather. Would it affect how long it takes to warm up or limit how hot it will run in cold weather?
                          Thats the same company that I bought mine from and it is still made in Germany, it took only a week to arrive from GB. It is still preforming well in my bike.

                          Comment


                          • #14
                            Hella, Meyle & Behr have replacement thermostats, Hella P/N is 2MT-002627-011, Meyle is 100 121 1025, Behr is 6.500.87.320 (sold by Mahle in US)
                            Last edited by WayneC; 04-25-2017, 12:45 AM.
                            02 Dakar

                            Comment


                            • #15
                              Considering the potential damage overheating, or over cooling, a motor can cause it seems to make sense to use either OEM or a quality replacement from a reputable company, like the ones Wayne has listed - risking a motor to save $30- doesn't seem much of a deal to me!
                              Adelaide Oz. 95 F650 Classic. 70 BSA B44, 77 R75/7, 86 R80 G/S PD, 93 R100GS.

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