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Discussion Starter · #1 · (Edited)
BACKROUND: This winter I installed a 450 big bore kit with 13.5:1, 2- ringed Wossner piston. I bled the system out of any and all air made sure the overflow tank was filled to the full line. I did have to deck the jug because the sleeve did fall down into the cylinder; not more then 2-3 thousandths. The machine shop guy said I could of probably ran it but I wanted to be safer then sorry. The jug was used when I bought it.

PROBLEM/SYMPTOMS: Recently I began noticing that the coolant level in my overflow tank has been rising. I thought maybe it was a possibility it may have leaked into the tank as I have had my quad up on it's grab bar a few times changing the stem bushing and nerf bars. This weekend in particular I drained out the excess coolant in my overflow tank and transferred it back to the radiator. The amount I drained out was just about the amount needed to fill the radiator back to the top (maybe a little less). Went to the track on Sunday and pounded the quad for 4 hours. It ran great, never missed a beat, very impressed with the 450 bbk power. Loaded up the quad, went home put it in the garage. Today, I went out to the garage to check the coolant level in my reserve tank. Sure as heck, the level was right at the top of the bottle. Looked in my radiator, realized it's about half empty.

OBSERVATIONS: Pulled the spark plug. Looks good. Doesn't appear to be burning coolant. I drained the system. Flushed it all out with a garden hose. I noticed a very tiny amount of black sludge in the bottom of my overflow tank. Pulled the thermostat and boiled to check it's working. It works.

BIG OBSERVATION: Tonight when I went out and pulled off the radiator cap, there was still pressure in the system as it made a quite a "puff" as I pulled it off. Keep in mind, the engine has been cold for about 20 hours so wouldn't the pressure have bled off in that time?

MY POSSIBLE IDEAS ON THE CAUSE: headgasket. Clogged line. Bad radiator cap.

If it was a headgasket, wouldn't I notice milky oil or a chalky looking spark plug? Why would there still be pressure in the system even after the engine has been cold for about 20 hours. Would this have something to do with my problem? Thoughts or ideas?
 

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I know you checked it and all but maybe try a different cap.........
 

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Could be a bad overflow hose as well. Will let coolant flow without leaking, but not hold a vacuum to pull it back, like a straw does.
 

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I have a rad cap here yours for 5 bux plus the ride.

lmk
 

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Discussion Starter · #6 · (Edited)
I have a rad cap here yours for 5 bux plus the ride.

lmk
Thanks Lopro.

Believe it or not, Advance Auto sells caps too part number 10233 for about 6 bucks. Tonight when I get home, I'm going to try and pull the pump cover to make sure none of the plastic fins broke off blocking coolant flow, check the return coolant line from the overflow to the radiator and put on a new cap. If none of these work then I may look into ripping the head off.
 

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Discussion Starter · #7 ·
UPDATE: First race of the season yesterday. Before I went out, I made sure the coolant was in between the low and full line on the overflow tank. Did 3 laps of practice; came back to the truck. The level was up past the full line. I waited and hour and took off the radiator cap. Even after the system has cooled off, it still had pressure. With the help of another, I blew on the overflow line and had the other person watch the radiator until it filled back up. At the point where it filled back up was where the coolant level was at full mark. (Pretty smart trick if you ask me!) Anyway, did (2) 4 lap motos. After every race, the coolant level was above the full line. The amount of coolant that I blew back into the radiator couldn't have been more then a half a cup. SO, if it is truly a headgasket leak, it must be pretty dang small because in those 4 laps I'm pounding the engine harder than ever. The quad ran great, never missed a beat and was able to nab 3rd place overall out of 7 that day.


I did change the radiator cap, flushed out the system, checked the thermostat. Maybe I need to check the return line for leaks?
 

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just to know, wich year is you're ltz ? I know it's written in you're bio but you could have another one :p i heard that the 2005-2006 had a recall on the clutch cover... the effect was pretty similar. The coolant would gum up in the circuit and would cause the coolant to go back in the overflow tank...
 

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Discussion Starter · #9 ·
2009.

The other concern I had I was the head bolt torque. In my manual it says max torque 33.5 foot pounds. BUT on the forum here, I've seen people use, 38 and 42 foot lbs? Which one is technically correct and maybe is it possible to re torque the head bolts to fix this problem? I used 33.5 foot lbs?
 

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check that vent hose for dry rot or a puncture of some sort. usually a blown head gasket will push combustion gases out the rad cap, not heave all the coolant out.
 

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Discussion Starter · #12 ·
check that vent hose for dry rot or a puncture of some sort. usually a blown head gasket will push combustion gases out the rad cap, not heave all the coolant out.


This is true. In theory though, if it can't leak through cap, once it builds up enough pressure to lift the spring in the cap, wouldn't it travel through the vent hose into the overflow tank? If there is a leak, it's got to be the size of a pinhole?


I will give the vent hose another glance. This time I will put pressure and suction on it to see if it has leaks anywhere.
 

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Sounds like head gasket to me. It's possible your sleeve slipped down into the cylinder creating a gap that will leak. The fact you said it moved down while cooling tells me it wasn't held down while cooling
 

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Discussion Starter · #14 ·
Sounds like head gasket to me. It's possible your sleeve slipped down into the cylinder creating a gap that will leak. The fact you said it moved down while cooling tells me it wasn't held down while cooling
It was a used cylinder I bought from another member. It was decked before I installed it. Hopefully it didn't slide down anymore as if it did, I'm sure the sleeve-crankshaft clearance is getting to close for comfort.
 

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Discussion Starter · #15 ·
UPDATE: Well I pulled the return line to see if it held pressure and vacuum by sucking and blowing air on both sides while I pinched the other end(s). No leaks. The only other thing I can think of is maybe a clogged or broken cooling fan? I took all the bolts off the water pump to see if I could pop off the cover just to see if the fan was broken or clogged but I couldn't pry off the cover? I didn't want to take the pump off but just take off the front cover? Other then that it looks like it may be the head gasket? Like I said, it seems to be transferring about 1/2 a cup each time it's ran which doesn't seem like its a lot? I am open to any more ideas before I think about tearing off the head.
 

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maybe i missed it, but have you checked the rad cap? is it allowing suction to vent back into the system?
 

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Discussion Starter · #17 ·
Yes. I bought a new cap at advance auto. Believe it or not, the same cap used on quads fits many american and Japanese automobiles. Its even the same psi rating. I cant figure out why it cant suck back into the system. Again, tonight when i pulled the cap off, it made a puff and air bubbled up into the overflow tank even after being cold for 48 hours after sundays race? Its holding pressure for some reason. If it was a bad head gasket, shouldn't it bleed into the cylinder?
 

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Discussion Starter · #19 ·
Sounds to me the hose is bad ..and it calapes when sucking, same concept with brake line go bad
It's possible. When I sucked on it, I couldn't physically see it collapse? I wouldn't think though that rubber hose would all off a sudden lose it's structural integrity and collapse under 16 lbs of pressure? I'm at a loss. I'm always open for my ideas. If it doesn't get any worse, I'm probably going to run it as it is. Once it has cooled off in between each moto, I'll just repeat that technique I mentioned earlier to blow the coolant back into the radiator via the overflow hose.
 

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Discussion Starter · #20 ·
So here is a new train of thought on this dilemma. WHAT IF: Being that a 450 iron sleeved big bore will probably produce more heat then the stock nikasil cylinder, maybe since it's running hotter, it's going to displace more coolant into the overflow simply because hotter anti-freeze expands more? Next time I ride, I'm going to let the overflow fill up and drain the excess fluid out of the overflow tank to where it should be. It seems like the fluid only raises to a certain point but has never overflown? Even though there wouldn't be as much coolant in the radiator, maybe it should work; granted it doesn't continue to push anymore fluid out?
 
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