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Reservoir/Overflow issue k7

2.7K views 12 replies 10 participants last post by  MadisonMotorsportUK  
#1 ·
So I just purchased an 06 gsxr 750 with a k7 (2007 gsxr 750 motor with 11k miles) the reservoir was full when I stopped for gas the temp was about 222 degrees the fan was running I cut the bike off about 30 secs to a min coolant comes rushing out of the overflow line. I rode home and watched the temp it never went over 230 degrees. I flushed the coolant out ran the hose water through it till it was clear, filled the radiator with engine ice filled burped it then filled the reservoir back up and again I’m riding come to a stop the temp goes up and all the coolant from the reservoir comes out the overflow tube. The radiator isn’t in the best condition either. Everything seems tight hoses clamps but I keep having this issue with the overflow and reservoir not holding coolant. Any input or advice would be helpful thanks
 
#2 ·
Check the neck on the radiator is nice and flat, and then buy a new radiator cap. It’s possible that the one on the bike is the wrong pressure rating or it’s stuffed.
 
#5 ·
Check the neck on the radiator is nice and flat, and then buy a new radiator cap. It’s possible that the one on the bike is the wrong pressure rating or it’s stuffed.

Appreciate it here’s a picture of the neck and right below the cap you can see there’s damage to the radiator and right underneath the cap it seems like the neck isn’t flush with the radiator. I just purchased a new one hopefully that solves the problem. I didn’t even notice that until I read your post big thanks!
 

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#3 ·
Welcome.

First, only fill the reservoir to the low line when cold (radiator totally full).

When the bike warms up, some coolant will come out due to expansion and should go up to about the full line.

When the bike cools, that coolant should get sucked back into the engine.

If this doesn't solve it, I would go with a weak radiator cap.
 
#6 ·
Did you take it for a test drive when you bought it?
Hopefully the radiator being bent is not an issue, as in closing the channels in it.

Good luck
 
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#7 ·
I did she ran fine wasn't overheating or had anything coming out of the overflow at that time. I went through all the gears, made sure the breaks were good but didn't really have space to get her running 80+ mph. Maybe 20 mins into driving on the highway the gas light came on and once I got off the exit traffic got a little slow and when I got to the gas station and took the key out starting pumping gas the overflow kicked antifreeze. I assumed because the temp went up and things got hot. But once I got home did my own flush and still had the same thing happen I knew something was wrong. Of course the shop I brought it from had said "Its normal for the reservoir to be empty, if anything comes from the overflow line when hot that's normal" but I should've known better just because of the condition the radiator was in not to just keep looking. But this is my first bike so I don't mind learning and doing things myself, whatever I can't fix or don't feel comfortable doing it'll go to the shop. My next GSXR whenever that is will most like come from a dealer!!! lesson learned
 
#8 ·
Shops are stupid. It's possible the cap is just bad, and I don't see anything bent on the radiator neck. But was the OEM radiator painted on that model? I don't think I've seen one painted before.

The expansion tank should never be empty. As the system gets hot, it will expand and pressurize. Since it's a closed system, the expansion needs someplace to go. The cap maintains a constant pressure of 12-15psi. So if your cap is leaking or won't hold pressure, the system will boil out coolant. If the expansion tank is empty, when it cools and contracts, it'll suck air. The system should never over flow. Once it gets to operating temp, expansion stops and the cap maintains the pressure so it doesn't boil.
 
#9 ·
50/50 antifreeze boils around 225 F and reaches 12.8 psi gauge about 260 F. So something is going on or it wouldn't be boiling at lower temps.

My OEM cap is marked Denso and 1.1. The service manual states that the radiator cap valve opening pressure is 0.93–1.23 kgf/cm2 (13.2-17.5 psi). I wanted to know for sure what the 1.1 value was so I contacted Denso USA, expecting them to say it was kgf/cm2 (1.1 kgf/cm2 = 15.6 psi). Instead they said that it was bars. That's nearly 16 psi. Go figure.
 
#10 ·
Radiator caps are cheap & universal as far as I'm concerned. I just took dimensions on mine & got one off ebay. Even if you didn't fix the problem, you are not at an entire loss.

Rule of thumb for diagnosing problems is replace cheaper parts first. Unless you're rolling in dough, who cares.
 
#11 ·
Rule of thumb for diagnosing problems is replace cheaper parts first. Unless you're rolling in dough, who cares.
1st Rule is to actually diagnose the problem before throwing parts at a moving target.
When that fails, as it often does:
2nd Rule of thumb for diagnosing problems is replace cheaper parts first.
3rd Rule: Save and Organize 'new-unused' parts in one place...That way, I have them available for future "Diagnoses Purposes". :rolleyes:
 
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#12 · (Edited)
You mentioned you burped the system, but make sure you’re doing it correctly. Air pockets can cause overheating and coolant overflow reservoirs. Ensure you follow the proper procedure for bleeding the cooling system.
Check for Coolant Leaks:
Hoses and Clamps: Double-check all hoses and clamps for any signs of leaks or loose connections. Even a small leak can cause coolant to escape and affect the system’s ability to maintain proper pressure and temperature. Given the symptoms—overheating, coolant overflow, and radiator condition—it’s important to address these systematically. Start by checking the radiator, thermostat, and water pump. Ensure there are no leaks and that the cooling system is properly bled. Inspect the radiator cap and overflow tube, and consider having the radiator pressure-tested if it shows signs of wear.
 
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