Race Bike rad/cooling issues

[PWesterdale]

Hi Guys,
Bought a ZXR400 race bike last year with the plan of doing some trackdays and then starting to race in about a year. I took it for its first trackday earlier this year to give it a run. First session was just to acclimatise to the track so it was about 8 laps going pretty steady. Went out on the second session at full pace and then came back in after twenty minutes, was just going to turn it off and then some coolant burst out of the rad cap.
I've gone through the process of clearing all the fluid out and replacing it, hoping that it might just have been an airlock, but I'm getting a bit worried about the next trackday and wether it will do the same.
The bike was used only for racing as a number two bike by its last owner, It doesnt have an oil cooler and the rad has been cut down slightly for the ram air intake.
Is there anything else i could possibly do to keep it cooler? would you recommend an oil cooler or should I be looking at a new rad?

Also from looking at the Rad the bottom left out tube is blanked off, can anyone tell me what that is meant to be and why it is blanked off?
(I can take pictures if required)

Cheers,

Paul.

[Davw]

Cant se how the radiator works if one of the inlet (or in this case - the outlet) is blanked off, The radiator can only work if there is both an inlet and an outlet. What is happenig here is that the coolant is not circulating - it also sounds as though the overflow to the header tank (on the rhs of the engine) has been blocked.

The radiator outlet should be connected to the water pump - what is the connection there? Has that been blanked as well?

[PWesterdale]

Sorry DavW, was having a bit of a stupid moment. It's bottom Right outlet if you were sitting on the bike, if that helps at all!

[hatatfatcat]

Has it still got the coolant expansion tank? This is quite important as the rad will dump water into it and suck it back and without it you will end up dumping water as you describe and end up with air in your system.

I think you need to put some pics up. My 'H' has no oil cooler and runs quite happily at 80 degrees. When you stop and switch the engine off it gets upto about 110 but doesn't dump water as the expansion bottle is fitted properly.

Do you know if the thermostat is still fitted?

[Davw]

Sorry DavW, was having a bit of a stupid moment. It's bottom Right outlet if you were sitting on the bike, if that helps at all!

Hi - photo would help but from what you say it sounds like the outlet that is blocked could be the thermostat housing - thermostat would be removed on a race bike as no fan.
It sounds like he overflow bottle is either missing or not connected properly. - post a coupe of pics and all wil be clear!!

[cargo]

Sorry DavW, was having a bit of a stupid moment. It's bottom Right outlet if you were sitting on the bike, if that helps at all!

Hi - photo would help but from what you say it sounds like the outlet that is blocked could be the thermostat housing - thermostat would be removed on a race bike as no fan.
It sounds like he overflow bottle is either missing or not connected properly. - post a coupe of pics and all wil be clear!!

There is no direct relationship between the thermostat and the fan. The fan is switched on and off by a switch in the front of the radiator (left side brass fitting)

The thermostat merely restricts the water flow until the bike is warmed up it's function is to speed the warming process. Racers (me included )remove it so as to maximise the water flow and have no restriction at all....................we (racers) always very carefully allow our bike to get fully warmed be fore starting a race or practise session (don't we ? )

[PWesterdale]

Hi guys,

Yes it was warmed up at the start of the day and still warm from the first session. The Temp gauge didnt register too high, and the coolant bottle is screwed in and on there, but didnt catch or have any fluid in it after the blow out.
I'm just going to take some pictures now and ill report back!
Thanks for all the posts!

[PWesterdale]

Hope that helps guys.

[cargo]

The only issue I see there is that your radiator may be a little low and therefore not a great enough head of water to fill the engine with water/coolant. ? ? ?

Also make sure the pipe into your catch bottle goes to the bottom of it and that the bottle can breath it needs to have a little hole at the top to allow it to vent/breath

[ratbag56]

that dont look like a zxr400 rad to me mite be off a 600 mayb

[cargo]

your right the fan switch is in the wrong place

[mark400]

1. That isn't a ZXr 400 rad.
2. It does have an expansion pipe outlet - this is the one just under the rad cap which is routed into a plastic bottle. I agree that it is best to have a proper expansion tank, I have used the standard one for years with no problems, but I have overheated an engine without one before.
3. The extra outlet which is blanked off on the lower RH side of the rad is blanked off because the zxr 400 has no need for this.
Finally, it is a bit surprising that the bike has pressurised the rad, but sometimes my brothers bike does this after a race, just as he is coasting into the pitlane. Incidentally, he doesnt use the zxr expansion tank, he also has a small bottle like your bike has.

[Davw]

If that small expansion bottle doesnt have a hole in the top to vent pressure as it fills then the system pressure builds up with no way of relieving. The height of the radiator shoudnt be a big issue as it looks as though it is still well above the highest point of the colling system in the engine. Might be worth checking that the line (spigot and hose) at the top of the rad into the expansion bottle is clear as it seems strange that the rad can pressurise enough to spill water out the rad without pushing at least some into the expansion bottle

[Davw]

THinking a bit more about this - whats the rad cap like? are the seals all ok? I am sruggling to see how there can be enough pressure to blow water out the rad but not into the bottle - unless the top cap seal is missing/ damaged

[lewisdale]

good point dave, thinkin about it ive seen similar things on cars, down to a fooked rad cap,