Thermostat or Water Pump

[97tiger885]

The 97 has been having cooling problems since October.   The gauge isnt spiking into the red but is moving oddly. For example,  it will be at the normal temp mark, suddenly drop to the bottom line for minute, then jump back to the normal temp mark.  It is not a gradual increase and decrease.  The fan is working.

The mc is definitely overheating.  This isnt an issue at 40 degrees but it is at 60, esp in stop and go traffic.

Is this more likely to be a water pump issue or a thermostat issue?

I have the Trident ready for head removal, so I can replace the Tiger thermostat with the Trident thermostat. 

I also have a used pump that I can put on the Tiger.  Is the pump fix swap-and-go or will I need to replace gaskets, o-rings and such?

Which should I do first?  Or should I do both?   I need to drain the coolant for both jobs, right?

[dave NL]

When overheating, is the coolant resevoir bubbling? Then the head gasket is leaking, this also causes the temp gauge to be erratic. It does not have to be in the red with a starting to leak head gasket, dont ask how i know....

During warm up fase the thermostate does its job, when warm it stays open. Usually when a thermostate brakes down or the function decreases it will stay open, so warm up fase takes a long time or does not warm up at all at low temperatures.

You can check the pump for piece of mind, check the axle and impellor that there fixated and run freely, it is a bullitproof thing imo. Only the bearings can go really.

A head gasket replacement is not the end of the world anyway, might this be the case,,,,,,

You will need a O-ring kit for the water pump, especially for the pump casing halves, this o-ring will harden over time.

[rybes]

i think its the temp sender that causes that. mine done it for a while till i stopped workin completly. the water pumps fine so it mustve been that. really wish i sorted it sooner cos it would saved me gettin a new engine from cookin mine 

[dave NL]

Yes, but a broken sender does not cause overheating....

[Sin_Tiger]

Just remember that the gauge temp sensor and fan controller are separate on Steamers.

[Bixxer Bob]

Just remember that the gauge temp sensor and fan controller are separate on Steamers.

That was helpful Sin.  So it looks like intermittent wiring fault on the gauge / loom / gauge sender  somewhere and a non-working sensor for the fan.  I don't have diagrams for a Steamer so I guess Mustang will jump in with the diagnosis tests.

[rybes]

Yes, but a broken sender does not cause overheating....

very true but it wouldve alerted me to the fact i had a lack of water 

[97tiger885]

When overheating, is the coolant resevoir bubbling? Then the head gasket is leaking, this also causes the temp gauge to be erratic. It does not have to be in the red with a starting to leak head gasket, dont ask how i know....

Ok, so to test for a head gasket leak, I can let the mc idle until the gauge spikes and see if the reserve coolant is bubbling?

During warm up fase the thermostate does its job, when warm it stays open. Usually when a thermostate brakes down or the function decreases it will stay open, so warm up fase takes a long time or does not warm up at all at low temperatures.

I am hoping the thermostat is sticking and unsticking.  Temp spike up as it sticks; temp spike down when it opens.

Not warming up at low temps doesnt help with diagnosis since the Tigers dont warm up in cold weather.  Isnt that what the winter shielding of the radiator was all about?

A head gasket replacement is not the end of the world anyway, might this be the case,,,,,,

End of world, no.  End of Tiger for me, maybe.   We will see how the Trident head gasket goes.  The Tiger needs some serious rehab at this point:  chain and sprockets, clutch, voltage regulator, valve adjustment.   I was hoping to nurse it along for another 5000 miles.

You will need a O-ring kit for the water pump, especially for the pump casing halves, this o-ring will harden over time.

I will need to order that before I do any swapping.

First I will check for a head gasket leak.


Thanks for the help.

[Bixxer Bob]

Which should I do first?

The easy stuff.  Guage is likely a wiring fault, check and sort it.

Overheating:  take the thermostat out and put it in water. Bring the water to the boil and it should open. If it does, it's ok, if not replace it. 

[ssevy]

You can also jump the fan wires to see if the fan is working. If your bike runs cool and the fan rarely comes on, the bearings can seize. Lots of used fans if you need one; just be sure the rotation is correct as some are push and some are pull.

[dave NL]

For the head gasket check...

-first check if the coolant is topped up!  :icon_wink:

- Then drive it like you stole it to heat it up, then stop alongside the road and take off the seat, when there are bubbles going in to the cooling water reservoir, 80% change of a BHG. (Do check the hose from the radiator to the reservoir)

[Sin_Tiger]

When you get the more complex cooling issues a really useful tool for diagnosing the root cause is an infrared non contact thermometer. They're inexpensive these days.

[Bixxer Bob]

Yup,  I bought one for about £10 when I was trying to work out which wheel bearing was making a bit of noise on my 4 x 4.

[97tiger885]

I have coolant in the radiator and the expansion tank.

The fan is fine.  The temp sensor is turning it on.

I put the Trident thermostat in the Tiger.  The Tiger thermostat opened in boiling water.

I let the mc idle until the gauge hit 2/3.  No bubbles.

Tomorrow I will run the mc hard , see if the thermostat switch makes a difference, and get it hot to check for bubbles.


dave NL:  I always thought it better to be a smart criminal.  That means no identifying tatoos and obeying traffic laws in stolen vehicles.  Dont make it  easy for the cops to catch you.   But I get your point.

[ssevy]

How is the condition of your coolant? If it is rusty you may have a partially plugged radiator, which would allow for some cooling except under high heat/load. I haven't seen this on my bikes, as I flush and change the coolant when needed and run good stuff in them, but I have had this happen to me with cars. It is also easy to get an air pocket in these when refilling, and this prevents coolant from circulating properly. Last idea is the heater hoses. They do age, and perhaps one is partially collapsed where it is difficult to see, and again, passes enough flow under light load, but not under heavy? I know when I swapped out a new starter on my buddy's Legend, the routing of the coolant hoses near the starter made it easy to partially compress them if not careful when reinstalling the new starter.