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Offline oldtexan

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Coolant Check Conflict
« on: November 04, 2018, 10:11:07 PM »
My owner's manual for my shiny new 2018 CB500xa says on page 70 "Check the coolant level in the reserve tank while the engine is cold".   My Helm 2013-2018 Honda Service Manual says on page 3-13 "Check the coolant level of the reserve tank with the engine running at normal operating temperature."

Can anyone resolve this apparent conflict?

Offline EscCtrl

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Re: Coolant Check Conflict
« Reply #1 on: November 04, 2018, 10:31:48 PM »
*Originally Posted by oldtexan [+]
My owner's manual for my shiny new 2018 CB500xa says on page 70 "Check the coolant level in the reserve tank while the engine is cold".   My Helm 2013-2018 Honda Service Manual says on page 3-13 "Check the coolant level of the reserve tank with the engine running at normal operating temperature."

Can anyone resolve this apparent conflict?

Always default to the owners manual. Most owners don't buy a service manual.

Offline oldtexan

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Re: Coolant Check Conflict
« Reply #2 on: November 05, 2018, 02:34:45 AM »
It makes sense to use the owner's manual as the final source.  Anyway,  it makes sense to check coolant levels when the coolant is cool, since you want to set the level so that even a hot motor will not overflow the coolant recovery tank.  Besides, cold engines are easier to work around.  Why would a procedure be set up that might require reducing the amount of coolant in the tank by having to suck out excess hot coolant with a turkey baster?

But why would the Service Manual say to check the coolant when the motor is at operating temperature and while it is running?  That is very odd.  And that Service Manual has been re-printed and added to several times.  If the coolant check procedure is wrong, it sure seems like it would have been edited.  But maybe mechanics never really paid any attention to the procedure, since it is so bizarre?

Offline EscCtrl

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Re: Coolant Check Conflict
« Reply #3 on: November 05, 2018, 09:58:24 PM »
With all the water pump problems I had, I checked my coolant levels both hot and cold. With my bike cold, the level seems to be higher. With it running, after a ride, the level seems to be only slightly lower. As the coolant heats up, it expands and flows into the recovery tank. When the bike is started cold, it usually pulls coolant back into the system. At least that's the way it seems to work on my bike. Keywords being "it seems to".

Offline Aggie95

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Re: Coolant Check Conflict
« Reply #4 on: February 10, 2019, 06:43:37 PM »
*Originally Posted by oldtexan [+]
My owner's manual for my shiny new 2018 CB500xa says on page 70 "Check the coolant level in the reserve tank while the engine is cold".   My Helm 2013-2018 Honda Service Manual says on page 3-13 "Check the coolant level of the reserve tank with the engine running at normal operating temperature."

Can anyone resolve this apparent conflict?
Old Texan,

There isn't really a conflict; each instruction is describing a different check.  I have a Honda Service Manual and it advises both tests.  Both inspections should be performed somewhat frequently.  The coolant system on our bikes is just like automotive systems that have been in use for decades. 

First is the cooling system which is comprised of the usual components and is sealed and pressurized.  There is very little air in these sealed systems to absorb the thermal expansion of the coolant.  Thus, the coolant recovery reservoir.  As the system heats, the coolant expands and is pushed out through a relief valve in the radiator cap and recovered by the reservoir.  When the systems cools, after operation, the coolant contracts and is drawn back into the engine/radiator through a check valve in the radiator cap.  The recovery tank is vented to the atmosphere. 

The volume of this fluid exchange should always occur within the Lower Level and the Higher Level marks on the coolant recovery reservoir.  If it's not too dirty back there, you will be able to see the coolant through the side of the reservoir.  The level should be above the low mark when cool and below the high mark when at operating temperature.

If the system develops a leak, the coolant exchange occurs at lower and lower levels until the reservoir is depleted at cold temps and air is drawn into the engine/radiator.  At that point, the pressurized side of the system system will require refilling and the air must be "bled" from the engine/radiator.  (see the repair manual)   :035:

The reason one should check the coolant when cold is make sure the coolant level is maintained above the lower level and prevent the need to bleed the pressurized side of the system.

The level should also be checked at operating temperature.  If air has been trapped in the engine, more coolant is pushed into the reservoir as the system comes up to operating temp because of the greater thermal expansion coefficient of air.  A high level at operating temp is a good indication of air in the system.

Sorry for the long winded answer; that's the engineer coming out. :034:


1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
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Offline SnowOwl

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Re: Coolant Check Conflict
« Reply #5 on: February 10, 2019, 10:12:50 PM »
 :460:
1980 Suzuki GS250T - Sold a long time ago
------------
1982 Suzuki PE175 - For exploring the farm with the dog
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Offline oldtexan

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Re: Coolant Check Conflict
« Reply #6 on: February 10, 2019, 10:33:01 PM »
*Originally Posted by Aggie95 [+]
Old Texan,

There isn't really a conflict; each instruction is describing a different check.  I have a Honda Service Manual and it advises both tests.  Both inspections should be performed somewhat frequently.  The coolant system on our bikes is just like automotive systems that have been in use for decades. 

First is the cooling system which is comprised of the usual components and is sealed and pressurized.  There is very little air in these sealed systems to absorb the thermal expansion of the coolant.  Thus, the coolant recovery reservoir.  As the system heats, the coolant expands and is pushed out through a relief valve in the radiator cap and recovered by the reservoir.  When the systems cools, after operation, the coolant contracts and is drawn back into the engine/radiator through a check valve in the radiator cap.  The recovery tank is vented to the atmosphere. 

The volume of this fluid exchange should always occur within the Lower Level and the Higher Level marks on the coolant recovery reservoir.  If it's not too dirty back there, you will be able to see the coolant through the side of the reservoir.  The level should be above the low mark when cool and below the high mark when at operating temperature.

If the system develops a leak, the coolant exchange occurs at lower and lower levels until the reservoir is depleted at cold temps and air is drawn into the engine/radiator.  At that point, the pressurized side of the system system will require refilling and the air must be "bled" from the engine/radiator.  (see the repair manual)   :035:

The reason one should check the coolant when cold is make sure the coolant level is maintained above the lower level and prevent the need to bleed the pressurized side of the system.

The level should also be checked at operating temperature.  If air has been trapped in the engine, more coolant is pushed into the reservoir as the system comes up to operating temp because of the greater thermal expansion coefficient of air.  A high level at operating temp is a good indication of air in the system.

Sorry for the long winded answer; that's the engineer coming out. :034:

No problem.  I always knew engineers were full of wind.

Offline CB-500-X

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Re: Coolant Check Conflict
« Reply #7 on: February 10, 2019, 10:40:16 PM »
That is a pretty definitive answer. And he's not full of wind just pressurized. :156:

Offline Superplasma

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Re: Coolant Check Conflict
« Reply #8 on: February 11, 2019, 09:37:35 AM »
*Originally Posted by oldtexan [+]
No problem.  I always knew engineers were full of wind.


Top post, thank you.

Superplasma.

Offline Aggie95

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Re: Coolant Check Conflict
« Reply #9 on: February 11, 2019, 01:38:42 PM »
Thanks All.  But, there is one more important thing I forgot to mention.

Having been a mechanic in my former life, I was also alarmed when I read that I needed to check the coolant level when the bike is at operating temp.  However, what is not very clear in the manuals is Honda doesn't intend you remove the radiator cap to do this  :110: (dangerous); they only intend you check the level in the recovery reservoir by visually observing the level through the back side of the tank.

1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
2018: '14 CB500X, The dream bike of my youth!  Thanks, Son

 


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