vt700 cooling system

[Scotch10]

Hi I have a vt700 and cooling fan will not come on as it should. I have checked wiring and fan works using the Clymer test. Have also tested thermostat its fine, and I have also fitted a new brand new thermostatic switch. I also fitted a radiator from a working bike. after all this the bike just heats up and steam comes from expansion tank overflow and fan does not come on. Its got me baffled

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Me too, if the switch, thermostat, wiring and fan is OK.
Clearly, at least one of those can't be fully OK.

The thermostat may open in hot water, but does it provide an electrical contact at the switch (edit - realised this is separate)? Are the meter readings correct?
Even with a non working fan though, should it be boiling? Is the water pump actually working?

I'd but one of those cheapie Ebay infared thermometer guns. You can then point them at varying parts, making sure you have flow around the cooling system. For £7 everyone should have one.

https://www.ebay.co.uk/itm/Digital-Non-Contact-IR-Infrared-Thermometer-Laser-Temperature-Gun/202726498616?_trkparms=ispr%3D1&hash=item2f3370e138:g:O-gAAOSw9m5cRome&enc=AQAEAAACUBPxNw%2BVj6nta7CKEs3N0qWdPFwh%2FxtOAE1NArX3yAwW%2FlhIhCyjHbhgGWsYm6YR77RQq79JTko8iRXHn9GO43mdyok06pyvCUYUAFrdJerUpD3cDyuzhR8BMuZHBnm8Loez4%2FPE7kRUgq5PxpmFk9VdhZfpmMYi%2FEwEa9bhdcaNOEaZF%2Bhxc43R8HA6beQIGYp2bpcflOOaJjRXYYhU%2F2XVz6IeYdrMLHvErRRTWfWHuEVd5J8WyZt1oW3LWOz%2FFasC4SyutYNJrKPnuQyqxcoanhhe3Lc1ECjzRZUBQBiyo%2BwvB0o%2BvyXrJh26ZbmIF8TtUa6fLBCp5DY%2BUvPc0elfmECURmOqzJqABtxFxzJCnbHiELvryk7SMb1r8cixPK7Ch6lNEisuKIyKz%2BgdkQyWNH5NDmQv363AjilCYXRT%2Fh%2Bkzc3ia%2BwDXfkZgEPyG1M4L0jek872Jn6WMVdQ3qKmZzThPondECDvWOoFTrA83rkiBTSCQ8rAFOzWvfAD3rJssQ4VrJ1S%2BPXvEBoK6i%2F9EGrPmz5locI6x9SbG7bvRl4P8qnpSFs5FimSF%2BS0M8sG5z9gubi2k2iQl0L0%2FL9CAVL8ydRu%2BdSJt%2FC0j%2FnnePDLy5jASn00t%2B8qtD6cxfrfNwLcZwBWVLdVobG911PUKl0y2foHL3r4RpgxEgJYrbkejIdre0aJkdeT51IHvm64Rgo0TUNMj56%2FRmLaeaEotfuiNVbPBt3idQKDPucS8BnQVUqadCPLCmClUvAgXFKCYozdkQfvkHnZSpP%2FVwY%3D&checksum=2027264986169f86a80e6b894564b5ff7c735cfb337f&enc=AQAEAAACUBPxNw%2BVj6nta7CKEs3N0qWdPFwh%2FxtOAE1NArX3yAwW%2FlhIhCyjHbhgGWsYm6YR77RQq79JTko8iRXHn9GO43mdyok06pyvCUYUAFrdJerUpD3cDyuzhR8BMuZHBnm8Loez4%2FPE7kRUgq5PxpmFk9VdhZfpmMYi%2FEwEa9bhdcaNOEaZF%2Bhxc43R8HA6beQIGYp2bpcflOOaJjRXYYhU%2F2XVz6IeYdrMLHvErRRTWfWHuEVd5J8WyZt1oW3LWOz%2FFasC4SyutYNJrKPnuQyqxcoanhhe3Lc1ECjzRZUBQBiyo%2BwvB0o%2BvyXrJh26ZbmIF8TtUa6fLBCp5DY%2BUvPc0elfmECURmOqzJqABtxFxzJCnbHiELvryk7SMb1r8cixPK7Ch6lNEisuKIyKz%2BgdkQyWNH5NDmQv363AjilCYXRT%2Fh%2Bkzc3ia%2BwDXfkZgEPyG1M4L0jek872Jn6WMVdQ3qKmZzThPondECDvWOoFTrA83rkiBTSCQ8rAFOzWvfAD3rJssQ4VrJ1S%2BPXvEBoK6i%2F9EGrPmz5locI6x9SbG7bvRl4P8qnpSFs5FimSF%2BS0M8sG5z9gubi2k2iQl0L0%2FL9CAVL8ydRu%2BdSJt%2FC0j%2FnnePDLy5jASn00t%2B8qtD6cxfrfNwLcZwBWVLdVobG911PUKl0y2foHL3r4RpgxEgJYrbkejIdre0aJkdeT51IHvm64Rgo0TUNMj56%2FRmLaeaEotfuiNVbPBt3idQKDPucS8BnQVUqadCPLCmClUvAgXFKCYozdkQfvkHnZSpP%2FVwY%3D&checksum=2027264986169f86a80e6b894564b5ff7c735cfb337f
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TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[Scotch10]

Yep things check out ok. Water pump seems to be working as liquid shoots out when engine revved with radiator cap off

[davebike]

If you got liquid (coolant I hope ) rushing out if you run the engine with the pressure cap off you probably have a blown head gasket compression to coolant Get it compression and "sniff" tested (sniff test looks fro hydrocarbons in the coolant )
____________________
Dave
NC750Xdct + others at work !
davebike1@gmail.com

[Scotch10]

Yep it is coolant but there is no trace of water in the oil as I say it only comes out when revving engine which makes me think water pump is ok is that correct

[davebike]

OK so if it only spues coolant when revved head gasket may be ok

So fan works if you put 12v across it ? Not stuck?
Fan switch provided earth ?
You have 12 the fan ?
there is plenty of coolant in the system fan switch will not work if not in coolant !
____________________
Dave
NC750Xdct + others at work !
davebike1@gmail.com

[Scotch10]

I checked the fan as you said following the manual. Fitted a brand new switch in radiator. The water pipes round the engine do take ages to heat up and coolant quantity is as per manual

[davebike]

YES BUT

So fan works if you put 12v across it ? Not stuck?
Fan switch provided earth ?
You have 12 the fan ?

Check the fan works when you use separate wires to connect it to the battery i.e. test it

is there 12v getting to the fan connector

is the fan switch actually providing earth when the bike is hot
is the body of the switch connected to earth?

changing bits at random sometimes works doing diagnosis just works ! YOU do have a multimeter don't you???
____________________
Dave
NC750Xdct + others at work !
davebike1@gmail.com

[Scotch10]

Yep I have multimeter I'll do checks as you have said and will get back to u thanks

[MCN]

You need to bottle test the cooling system.
This test shows excessive gasses in the cooling system.
There is normally a little steam (gas) but excessive gas can only be from combustion gas leaking into the cooling system.
Blown gasket or cracked head.

It's not a simple test but it helps confirm combustion gas in the coolant.

I think there are chemicals that can be added to coolant that change colour when combustion gas is combined with them.

Also, a dead pump will cause water to be held in 'hot spots' long enough for steam to be produced which will push water out the top tank or expansion tank.

To check pump circulation.
Open a hose clip and shove a screwdriver up the hose until the coolant drips out.
Start the engine and look for the drip to change to a dribble or increase even slightly.
A working pump will create enough flow that will generate a pressure rise in the system.

(Pumps do not create Pressure. They only create flow. Restrictions to flow change pressures. It's the Law.)
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Scotch10]

Hi again have done multimeter tests all checked out. I'm not convinced about any blown gaskets or cracked head.When I turned engine off I could hear the coolant boiling.

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[Scotch10]

No for some reason the brand new radiator switch doesn't kick in totally stumped, cross the wires as if switch has opened and fan comes on with bike running or not. Checked fan with spare battery aswell no problem

[Monkeywrenche...]

It Could also be a faulty radiator cap, they are designed to open at a certain pressure (related to temperature) to allow expansion into the tank, they should then suck it back in as it cools. if the spring has weakened it may be opening before the temperature reaches the point of triggering the fan.

The poit of pressurising the system is that without pressure the coolant will boil at or befor the normal operating temperature so low pressure will cause boiling.
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2001 Aprilia RSV Mille R -dead, 2016 XSR 700-gone, 2018 Dorsoduro 900

[Scotch10]

Thanks I'll try new cap

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[Scotch10]

Yep but I have tried second hand switches aswell surely cant all be faulty

[Robby]

A few bits seem off.

You mention steam coming out of the expansion bottle. The expansion bottle should have coolant in it up to the line, and the pipe from rad to bottle should be at the bottom of the bottle. This means that any steam coming from the rad is spat out into the bottom of a bottle full of liquid, and should condense back to liquid before it gets out the top of the bottle.

So check your pipe routing.

Next up in radiator cap. If that isn't working, then it isn't letting the system pressurise. This means the coolant is boiling at ~100 degress, rather than ~115. New rad cap is worthwhile.

Finally, it could just be air in the system or a pig to bleed. So before fiddling with it too much, do the following:

1. Change the rad cap.
2. Check the routing of the pipes, to make sure the pipe from the rad to the expansion tank exits at the bottom of the tank.
3. Make sure the system is filled up, and the expansion tank has coolant in it up to the line.

Then run the bike up to temperature, turn it off, and walk away for at least an hour. If the level in the expansion bottle has dropped, it had air in the system which is now replaced with coolant. Refill the bottle, do the same thing again.

Only once you are sure that the system is full and working properly should you start looking at the fan switch and its associated wiring. You can test them in a pan of hot water. If the wiring is done well, the fan switch is probably used to trigger a relay, which powers the fan - so check/change that relay. You could even run it as a whole new independent circuit off the battery. It will only draw power when the engine is very hot, so it won't flatten your battery just sitting there wired into the battery.

[Scotch10]

Thanks Robby I'll give all that a go

[Sister Sledge]

Although I'm not familiar with that actual cooling system - some cooling systems have an air bleed screw separate to the expansion tank. Does this bike have one? If it does, has it been bled of air?

Edit: Mine actually has a few and one of them is on a radiator - if air is in that radiator then the thermostatic fan switch will not operate because they need actual coolant to be touching them to operate.
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CCM 404 DS

[Scotch10]

It does have a bleed screw on thermostat housing but manual only refers to this when emptying the coolant.