Boiling expansion chamber tank

[Andybarnes180]

Hi, I have recently had the carbs off my 86 voyager, got in running again but now the expansion chamber for the coolant begins to boil...and steam out the over flow. I have had the thermostat off, it opens in the boiling water, bleed the system, several times, topped it up...partially looked at the water pump, i.e. If it was clogged. Nothing! Why might it boil? It drains ok, ran fine before? The temp gauge though has always been faulty, ...please any ideas. I can try sorting a video of it boiling for your amusement...thanks andy

[triton28]

In a perfect system having unobstructed coolant circulation, ambient temperature air flowing through the radiator core and an operational fan and switch there would be NO boiling.
I would first make sure the hose that runs from the radiator cap fitting to the overflow tank is NOT obstructed. Take the hose off the fitting and make sure you can blow air through it into the overflow bottle, although it sounds as though it is not blocked but it may be partially blocked.
Next I would ensure that the fins of the radiator cores are not smushed together. The air needs to pass through the cores unobstructed. Straighten out any bent/jammed together rad fins as best you can.
More likely though, something is partially obstructed/blocked downstream of the thermo housing. My money is on the radiator core being blocked and the 1/2" bypass hose is directing the hot water from the cylinder head outlet pipes back to the water pump, bypassing the radiator cooling cores and delivering hot water to the pump to send back into the engine and get even hotter and so on and so on.
If it were me I would remove all of the hoses/pipes and radiator, check them for debris/crud and flush, if possible, the radiator. Then I would reinstall all of those items, with new o-rings/gaskets if needed, and add some Prestone, ( or equivalent ), coolant system flush and follow the directions of the manufacturer with respect to engine run/coolant flush circulation time. Hopefully it won't boil in the expansion tank while using the flush. If it does I would say the rad is blocked.
Then drain the coolant flush and fill and drain the system with rinse water several times more. Fill it a third time and then run the engine and see how it works then. If after checking the hoses/pipes and flushing the system with cleaner/flush the boiling persists, I would have to say the radiator has blocked cores and did not allow enough coolant flush to pass through and sufficiently clean all of the cores of the radiator.
There really isn't anything near the carbs connected to the cooling system except where the throttle cables pass over the LH cylinder head coolant hose and some small diameter "clean air system" hoses above/around the RH cylinder head hose.
I understand it was working ok, but it may be a coincidence that this problem started after your work. As I often say; everything has to start sometime and this may be the time for your cooling system to act up.
As a side note you should be using a blower fan to cool the rad water while running the bike at a standstill. Even though the radiator fan will cut in and out, it may not be enough airflow to lower the temperature of the coolant, provided the coolant is indeed flowing through the radiator.
I hope someone may have a simpler solution to offer,
Dave

[Nails]

I would first make sure the hose that runs from the radiator cap fitting to the overflow tank is NOT obstructed

Ironically, this morning I found that mine is. Only noticed it because the hose from the cap to the radiator was collapsed.

remove all of the hoses/pipes and radiator

I understand that the upper radiator hoses cannot be had for love nor money, and that the o-rings are a common failure point. Anything else I should watch for?

I see a scad of o-rings:

• 92055-1266 (1, water pump, probably don't need)
  92055-1324 (1, thermostat, probably don't need unless I get in there)
  92055-1325 (2, thermostat pipes)
  92055-1328 (1 for thermo body to thermo pipes, probably don't need for the 2 for the coolant pipes)
  92055-1350 (4, cylinder pipes, probably don't need)

My temp gauge doesn't work and the ground trick didn't fix it. I'll test the sensor while I'm in there. The fan works, though. (I think I'll wire a dash light to show when the fan is on.)

[triton28]

In the Dollar4Dollar portion of the Tech Center located on the AVA Home page there are listings for alternatives to the stock front hoses.
The bypass hose is listed as Gates 10076 but I believe that is a typo as the closest hose I could find was a Gates 18076. It is 1/8" larger on the small diameter but with clamps should tighten up sufficiently to work. The large 3/4" diameter end would I imagine be cut off to provide the desired length. I haven't had to try this 18076 hose yet myself so this is speculation on my part.
The Dayco larger hoses are slightly larger in diameter than OEM being Imperial in measure, but will work.
The LH cylinder head outlet hose is the hardest one to replicate/substitute and to date no alternative moulded one piece hose has been found. Looks as though these cyl head hoses are going to be the ones to watch out for in NOS sales.
A long 12 inch plus 1/4" extension and a 6mm socket is the way to go. I found that the t'stat housing to the radiator is the hardest hose to get on. I leave it loosely clamped on the t'stat spigot, extended farther forward than normal, then fit the radiator into the hose, tighten the clamp of the radiator end of the hose and then push the assembled hose onto the t'stat spigot whereupon I then tighten that clamp last.
Use soapy water or a smear of non-petroleum based brake grease to aid in getting the hoses on. DO NOT use regular grease as it will soften/expand rubber.
Hope that helps,
Dave

[Andybarnes180]

Brill, thank you for the reply. I have a busy morning ahead. I ll hopefully find something. Cheers

Andy

[Nails]

Thanks for all the info about the hoses. Timely.
My overflow line was totally pinched between the fuel tank and pump. Had been that way a long time. Sheesh.

[Andybarnes180]

So someone mentioned a head gasket gone, this sounds like. Nightmare.....I have the rad off, it looks ok, struggling to get pump off, so do I need to take exhaust off? No obvious crud in the pipes though? Top pipes are fine, thermostat opens, blown clean through over flow pipe, all clear. The fan works via jumper wire, maybe the fan temp switch or temp sensor? The impeller is firm which I think is a good thing. But a leaking head gasket, a whole new school of thought. So experts across the pond, is this possible? I know it's possible but on this engine in these Circumstances? Anyway any ideas before I set out on a mamouth task would be really helpful. Thank you...

[cranky]

.. NOT a wrench, but wouldn't a compression test show a leaky head gasket?

[Mr Jensee]

...and Andy, I prefer a 50/50 premix of antifreeze. It is easier than trying to measure it out on your own, cheaper as 1 gallon of it is all you need.

[cushman eagle]

.. NOT a wrench, but wouldn't a compression test show a leaky head gasket?

Yes, crankyb,a compression check can indicate a leaking head gasket,if it is leaking enough .It would not necessarily leak at cranking pressure,but could still leak at combustion pressure,which is higher than cranking.I have seen head gaskets which did not leak until the engine was near full load,as the gasket was beginning to fail.

[Andybarnes180]

https://youtu.be/dIW6h0LSY3Q I should one of the videos.

A second link is https://youtu.be/shZC23rcabo


I still have nt got any further....I need to put it back together and see what the steam smells like I think. I can then do a compression test.

Any further thoughts, let me know.

Andy

[Mr Jensee]

For a small fee a local radiator shop could clean out and pressure test the radiator. Sounds like you have an obstruction and if the coolant hasn't been changed in over 5 years there could be a buildup of sludge in your core.

[Nails]

Michael, I'm thinking you might be an expert on buildup in one's core.

[Mr Jensee]

I dont know about being an expert but I have had some clogged pipes to contend with.

[cranky]

... used to have... Get 'er fixed and back on the road!!! You should
start feeling much better!!!!!

[ekap1200]

Hi, I have recently had the carbs off my 86 voyager, got in running again but now the expansion chamber for the coolant begins to boil...and steam out the over flow. I have had the thermostat off, it opens in the boiling water, bleed the system, several times, topped it up...partially looked at the water pump, i.e. If it was clogged. Nothing! Why might it boil? It drains ok, ran fine before? The temp gauge though has always been faulty, ...please any ideas. I can try sorting a video of it boiling for your amusement...thanks andy

Hello from NJ. Well after reading this, I see that IT RAN FINE BEFORE. Well before what ? pulling the carbs and doing what ? If it ran fine before then it should run fine now. What have you done to change things and just how long are you letting it run without going down the road. This cooling sys is not like a car where you can let it run and run and run for 15 to 20 minutes. You need keep quite a bit of air flowing on the bike when just sitting there running. Even doing a carb sync. you either have to know how its done and be quick about it or get a BIG fan and keep this engine cooling. They can overheat much quicker than a car..... Having no temp gauge is not good. check the ground and not just add one, look at the lead from the stat and trace it over to where it plugs into the main harness on the right side it may not be a bad ground but the gauge wire itself. Or just check it with an ohm meter first. Do not just ground the
gauge wire , tap the wire for just a second to see it the gauge needle moves at all. If you leave the lead grounded and the gauge pegs out the small wire winding's over heat and destroy the gauge head. Chances are nothing new has happened but something that has been overlooked as your saying it ran fine before.
Gene Kap.

[Andydesperado]

Hi, I have been really busy with life, now back to this point again I’m checking the oil for gloop, rad cap, maybe a head gasket on the inlet side. I’ll keep you informed.....

[Bill O]

Sounds like you might have crimped the overflow hose line going to the overflow tank when you re-installed the tank. Been known to happen. This blocks of the radiator getting coolant and the radiator just boils over to the point that the line to the tank just boils through fron the excessive pressure. Pull out the radiator overflow tank and check the hose line going back to the radiator. The second hose from the tank just drains to the ground behind the swingarm.

an easy check.

Bill O

[Nails]

I would first make sure the hose that runs from the radiator cap fitting to the overflow tank is NOT obstructed. ... although it sounds as though it is not blocked but it may be partially blocked.

Mine sure was blocked, between the frame and the second airbox as I recall. But I also don't think the overflow tank has anything to do with it. I bet the engine just got hot and vented out the overflow tank -- as it should.

I consider a good radiator flush to be necessary maintenance; and I bet there are a lot of XII out there that never got one.

First, I'd drain the coolant -- check out how skanky it is. Then fill with cheap water and try to assess whether that circulates: does the bike overheat right away? If so, I'd take the radiator to a shop and ask them to vat it, if not rod it out. They should be able to assess whether it's blocked as well as fix it (or wreck it trying). Maybe this isn't necessary, but even so I don't think the cost is totally wasted.

Hopefully, the coolant is circulating at least a bit. I also like Prestone flush, and you get enough to doit at least twice -- I sure needed to. Run it for a quick jaunt and then prepare to be shocked at what it looks like draining out. Repeat until you run out of flush, and at least once again with distilled water. Then see if it overheats on the DI -- if not, problemo solved. But either way, replace the hoses and o-rings (inspecting as you go). Also not wasted even if not strictly necessary.

I suppose there's a chance the water pump crapped out.

But hopefully (again), a good flush will get it, and you'll be able to put in some antifreeze and go ... and do apologize to it for not flushing it sooner.

[ekap1200]

Hi, I have recently had the carbs off my 86 voyager, got in running again but now the expansion chamber for the coolant begins to boil...and steam out the over flow. I have had the thermostat off, it opens in the boiling water, bleed the system, several times, topped it up...partially looked at the water pump, i.e. If it was clogged. Nothing! Why might it boil? It drains ok, ran fine before? The temp gauge though has always been faulty, ...please any ideas. I can try sorting a video of it boiling for your amusement...thanks andy

Let us retrace, " ran fine before " ! If it ran fine before you pulled the carbs than maybe something has been overlooked.. I have to ask, do you have a book, and from where did you bleed the sys ? It only needs the pump bled . Things don't break down just sitting there and if you even think the head the problem, with the bike cooled , top off the rad and run it a few min. with the cap off. look for bubbles. In short go back over everything you did, let us know what you find.
Gene