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OVERHEATING! Help to diagnose 2011 ABS

Gen 4: 2011-15 
4K views 21 replies 9 participants last post by  zxbiker 
#1 ·
Hey community,
I am a bit perplexed about what is happening with my 2011. I was hoping one of you nows a lot more about this than I do and could possibly help me figure this out. Here are the details:

The bike ran a bit hot during late August/September (thats when i got the bike). It would normally run in 220+ range (even after the fan kicked in). I've had 4 other zx10rs and i thought that all of the previous ones ran a bit cooler. So anyway. I was riding a week ago in a 65-70 degree weather and as i came to a stop at an intersection i saw the temperature start to rise past 230. It got to 235 and then i looked down to the right side of the bike and noticed vigorous bubbles coming out into the overflow coolant tank to the point that it started bubbling over and i started dumping coolant on the pavement. I immediately turned of the bike and let it cool down and parked it. I lost about 1/2 quart of coolant in that incident. So i went and got more coolant and topped off the radiator (it was 50/50 premixed). Started the bike --> no bubbling anymore and the temp does not get over 203-205 while standing. A few days latex i start seeing the temp go higher to 215 or so. The temperature now is very unpredictable - the temp goes up for seemingly no reason ( i.e. i would not predict the temp to get to that point based on the riding, airflow and RPM). I think there is something going on still.

Things I've done:
-sprayed down the radiator on the outside with a brake cleaned to make sure the fins let air thru (helped a little i suppose).
- When i put my hand on the thick rubber coolant hose on each side of the bike and rev the engine --> i feel the pressure build --> so i think the pump is pumping ( at least a little).
-i don't see any leaks under the bike when i park it, but immediately after seat of the bike (after its been sitting for a day or more) i think i smell coolant burn by the radiator/header area. ( I THINK).

What do you guys think may be a problem? How can you explain the symptoms? I was doing a bit of research and there was mention of blown head gasket (when you see bubbling). But i would imagine that you would be bubbling all the time. But ever since i topped off the radiator, there hasn't been any bubbling happening in the reservoir (there would be bubbles, i think, if its constantly blowing exhaust into the coolant system).
Could it be that the slight leak in the system sucked in enough air to cause it to expand enough to bubble over? Or maybe there has been water in the system? (but it looked greenish). Or maybe its the bad thermostat is what causing the variable temps...

Help me out guys!
Thank you
 
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#3 ·
I just fixed the same issue with my ZX-7R. First things first, start with the easy stuff and go from there.

What's happening is you're boiling the coolant. Water boils at 212 degrees under ideal conditions. Anti-freeze doesn't change this, it keeps the water from freezing and makes it a lubricant for the pump and anti-corrosive. What keeps the water from boiling is the pressure. Remember from science class in high school that you can make water boil at room temp if you drop the pressure low enough? Well, the opposite is true is you increase the pressure. This is how pressure cookers work. Increase the pressure and water won't boil until it's much higher than 212 deg. So, you're not maintaining the pressure in your bike.

First thing to replace is the radiator cap. The whole purpose of this piece is to keep the pressure at 14-18psi to keep the coolant from boiling. But as the water gets hot and expands, it goes out into the reservoir tank and as it cools and contracts the water gets pulled back from the reservoir into the engine. There should be no air in the system of the pressure balance goes out to whack and you boil it out into the reservoir. The radiator caps job it to keep the pressure up, yet allow the coolant to move in and out of the engine as it expands and contracts. Cheap and easy as they can fail.

Problems get more complex from there. If the radiator cap doesn't fix the issue, it's likely you have a leak somewhere else which is causing air to get into the system. The second most likely place with will happen is a faulty head gasket. This is what it turned out to be on my ZX-7R.

I replaced the radiator cap, thermostat, thermostat housing, fan switch, cleaned the radiator, checked the water pump, pressure tested the block, and in the end it was a bad head gasket. Combustion pressure was overwhelming the gasket at high RPM and blowing air into the cooling system. Air in the system = no pressure = boiling coolant = over heating.

Do not ride the bike any longer until you get this sorted out. Since you're boiling the coolant and getting air in the system, the reading your seeing on the gauges is not accurate. The sensor only works well when submersed in water. Since you have air in the system, the temps are likely higher than what you're seeing. And severe engine damage can occur at 230-240 degrees. In 80 degree outside air, cruising down the street, the bike should be running consistent temps in the 180 degree range. Fan comes on at 212 degrees and the shutdown "HOT" warning at 239 degrees. I hope it's just the cap in your case.
 
#4 ·
thank you for reply. wouldn't you think that if its the head gasket then i would be boiling coolant consistently? because since i topped it off with 50/50 mix, i haven't seen any bubbles. :dontknow: the temps are better but not stable now. i will definitely replace the cap. I'm trying to reason what would happen if the head gasket was letting exhaust into coolant system.
 
#12 ·
We're ok to about 250f plus some, if I recall. I would add a couple tablespoons of water wetter to the reservoir and make sure the level is up to the line. I go past the line.

Now I know this is gonna disturb everyone, but I WOULD change the oil often and the filter until the temp goes lower. use amsoil syn and their little filter. Don't do any other oil at this time. Heat is a major problem for even good oil so I would change the oil

My g4's always run cool unless idling at a stupid traffic light or running up a steep mountain section in heat at high rpms but even then it's like 203f and sitting at the light in heat it's not above 212f.

the above is on both the '11 and the '13 in normal humidity as in NOT dry desert stuff. I'm in the Monterey Bay CA, USA area.
 
#13 ·
Thank you guys!
I havent gotten a change to get to it yes. Been working a lot. My immediate goal is to flush the system and get a new cap. Also, whats the best thing to use the clean the radiator on the OUTSIDE? It looks like it picked up some grime from the wheel. I tried brake cleaner but couldn't get it all off. Should i try a carb cleaner?
 
#16 · (Edited)
g4, right? just buy water wetter and put a couple tablespoons into the reservoir. Have to buy a flex hose funnel then just pop the plastic crap rivets, three, on the bike's right, on the plastic next to the fork to get to the cap.

Then make sure the water level is right. I always go past the line but you make that decision. I go past the line cause I hate filling the water all the time. lol

My thinking is that if water wetter doesn't get things cool the water pump is thermostate is dorked. So I wouldn't change the coolant until I knew the pump etc was working. Or you'll be doing it twice. I know how to avoid things, sometimes.
 
#19 ·
skydork
have the same soap opera with my gen4 after a accident.

If you let it idle looks perfect, when you start hamering the bike if starts doing all the strange stuff.

going to change the head gasket.

was tempted to use the thinner one, but dont know anyone that has done it with not moving the cams.
 
#20 ·
Replaced the head gasket...no more bubling now but reservoir is getting some coolant still from radiator.

I took out the thermostat and runs very cool like 78C when running, when it stops gets a bit hot.

Skydork how do I check the block???

I will get parts sonn and see.....
 
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