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Gsxr 750 dumped coolant during a ride

fan stays on?

After a spirited ride, will your radiator fan stay on after engine cutoff? if not, that could be your problem. The radiator fan should stay on for a time after engine cutoff to cool the system a bit and to prevent overflow.
 
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Hank Wong said:
After a spirited ride, will your radiator fan stay on after engine cutoff? if not, that could be your problem. The radiator fan should stay on for a time after engine cutoff to cool the system a bit and to prevent overflow.
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It doesn't. The fan shuts off when the ignition is turned off.

The ride up old san Jose into Saratoga and up 9 to skyline where I stopped was spirited.. I did turn the ignition off when I stopped to stretch my legs.
 
PaleHorse said:
It doesn't. The fan shuts off when the ignition is turned off.

The ride up old san Jose into Saratoga and up 9 to skyline where I stopped was spirited.. I did turn the ignition off when I stopped to stretch my legs.
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Keep watching the coolant level in the engine/radiator. The last you want to do is ride w/o or low coolant.
 
Busy Little Shop said:
Possible boil over from the catch tank... proper order of items to trouble shoot are:

1)Faulty radiator cap... system should hold 1.1 pressure ratio...
2)Insufficient coolant...
3)Passages blocked in the radiator, hose or water jacket...
4)Air in the system...
5)Thermostat stuck closed...
6)Faulty temp meter or thermo sensor...
7)Faulty fan...
8)Faulty fan switch...
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add fan FUSE to this list.

check it before next ride; ignore if you hear fan coming on?
 
If you have no air in the lines and everything is good. Definitely check your radiator cap first. Now what you can do is get a racing high temperature racing gas cap which raises the boiling temperature of the water higher thus preventing boil overs and small leaks from the overflow tank.

Instead of 1.1 pressure ratio you can get a 1.8 which will raise boiling temperature to 26 degrees more. I know you're going to do a spirited ride on a hot day and you park your bike in your garage or parking space and the next morning you'll notice a small puddle of boiled over coolant on the ground. The cap fixes that.
 
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Paulo666 said:
If you have no air in the lines and everything is good. Definitely check your radiator cap first. Now what you can do is get a racing high temperature racing gas cap which raises the boiling temperature of the water higher thus preventing boil overs and small leaks from the overflow tank.

Instead of 1.1 pressure ratio you can get a 1.8 which will raise boiling temperature to 26 degrees more. I know you're going to do a spirited ride on a hot day and you park your bike in your garage or parking space and the next morning you'll notice a small puddle of boiled over coolant on the ground. The cap fixes that.
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I believe OP has replaced the cap.

Yes, it will raise the boiling point of the coolant. But with the potential downside of raising the pressure of the system which increases the risk of leaks. No matter how spirited OP's riding is, it just doesn't get hot enough around here to justify the use of a higher pressure cap. If his cooling system is in good shape, he should be fine.

Also, a higher pressure cap will have zero effect on any leaks from the overflow tank. That part of the system is not pressurized and as long as it's in good condition (see my earlier posts), it will function without leaks, accepting coolant from the main cooling system as the coolant heats and expands and then allowing coolant to be sucked back into the main cooling system as the coolant cools and creates a vacuum.

As I mentioned before, if there are ANY leaks in the overflow system, air will get into the main cooling system as the engine cycles hot/cold/hot/cold and eventually the main system will burp air which is what forces coolant out the overflow tank which is vented to the ground.
 
Long as your hoses are fairly new and clamps are good. You shouldn't have any problems with any leaks using a high pressure cap. The cap actually designed to keep your engine from overheating by maintaining high pressure inside the cooling system thus increasing the boiling point of your coolant and my bike actually runs cooler this way.

It provides a safer and more efficient cooling system and prevents boilovers.
 
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Think I have it narrowed down to the filler neck. I flushed the system, checked all of the hose clamps and replaced the cap with an OEM. Took it out again today and it boiled over again. The top of the filler neck it pretty beat up and I dont think the cap is making an adequate seal letting air into the system. At 219 degrees on the temp gauge the coolant boils into the overflow tank.

Can these be repaired or is it easier to replace the radiator?
EDIT- ordered a new radiator tonight. Is there any benefit to silicone hoses? They are about the same price as a full set of oem hoses.
 
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PaleHorse said:
Think I have it narrowed down to the filler neck. I flushed the system, checked all of the hose clamps and replaced the cap with an OEM. Took it out again today and it boiled over again. The top of the filler neck it pretty beat up and I dont think the cap is making an adequate seal letting air into the system. At 219 degrees on the temp gauge the coolant boils into the overflow tank.

Can these be repaired or is it easier to replace the radiator?
EDIT- ordered a new radiator tonight. Is there any benefit to silicone hoses? They are about the same price as a full set of oem hoses.
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Well the first two things I would suspect is the radiator cap and the thermostat. You can easily see if the neck isn't round inside the filler neck.
 
If the sealing surfaces in/on the neck aren't in too bad condition, then perhaps some wet or dry sandpaper might smooth things up. But I'd remove the radiator for the work and then flush it out well to remove any grit and particulate.

There are two sealing surfaces. One on the very top of the neck. And the other is down inside the neck.

If you haven't checked your thermostat at this point, I'd do it. I had a coolant hose to one of the heads on my ST blow out in the middle of rural Oregon once. At the time I replaced the hose while on the trip and I got home though the coolant seemed to be running hotter than usual. Still within the normal range, I made it home fine.

I then decided a complete freshening up of the cooling system was in order and when I pulled the thermostat off the bike, I found the reason for the overheating. The little swaged ring that attached the valve to that plunger thing that presses on the valve and opens it had failed. What happened when it failed was that the plunger thing could no longer press against the valve to open it and since the engine was running, coolant flow kept the plunger shaft in the center of the now closed valve, effectively blocking all coolant flow except for through that tiny bypass hole that's in every thermostat. The engine overheated, blew the hose and that was it. When I shut the engine down, coolant flow stopped and without anything to keep the plunger in place, it fell down inside the thermostat housing. Then, after I replaced the hose and buttoned everything back up, there was just enough flow through the center of the closed valve to keep the engine in the proper operating range. It wasn't until I went through the coolant system that I discovered the reason it overheated. Once I saw the reason, I went searching for the broken piece and found it by turning the radiator upside down and flushing it out with a hose.

So, it's possible that you have a thermostat problem. And if you're going to the trouble of getting to it, replace it with a new one. Even a thermostat that looks good can still be bad.

I'd try that before fooling with the radiator.
 
I'd stick with the factory hoses. Silicone hoses are OK, I suppose, as long as they are designed for pressurized cooling systems.
 
ST Guy said:
I'd stick with the factory hoses. Silicone hoses are OK, I suppose, as long as they are designed for pressurized cooling systems.
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I'm with you on freshening up the whole system. A new radiator, all hoses, clamps, thermostat and temp sensor have been ordered. I pulled most of it apart this afternoon. The gasket on the thermostat looked a little rough. I put the old one in a pot of water and it functioned correctly. Fully opened at 117 degrees. All the new parts will be here in about a week.
 
Replace the thermostat. Just because it opens at zero pressure, that doesn’t mean it will work properly in your cooling system. Thermostats are inexpensive. And you have it all disassembled anyway.
 
Status update

Looks like I've got this one licked. While my best guess was that I was not getting and adequate seal at the radiator cap but I'm not entirely sure.

All the parts showed up today. I put in a new radiator, cap, hoses, thermostat, impeller and fan control switch. I'm also running water wetter/distilled water and 15% amsoil anti freeze. (The water wetter bottle recommended adding the anti freeze for street riding)

I got everything together. Filled it, leaned it side to side, warmed it up and bled the system. Rode it around the neighborhood, let it cool and topped off the radiator and overflow bottle. Kind of a hybrid between the clymer manual and factory service manual.

I went out on a longer ride in the SC Mountains. The bike averaged 184 degrees with no boil over or leaking. The biggest difference is the fan now kicks on at 186 degrees. It would kick around 210 with the old switch.

I'm positive the bike came with this problem as it had a 1.8 bar cap on it when I bought it. Everything looks good with the 1.1 bar factory cap.

Thank you for all the help and advice on getting this fixed!!:thumbup
 
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Most excellent. And yes, for street use, some anti freeze is highly recommended. It helps keep the water pump seal lubed. Happy riding!
 
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