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head gasket or radiator cap

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last night i was getting my bike ready to ride to work today & noticed the overflow tank about 3/4 full - much fuller than normal.

after noticing that, i opened the radiator cap & a lot of pressure escaped.

my ist thought was head gasket, & searching TT this morning seems to back that up.

i didn't have much time to mess with it, but i am wondering if the pressurized rad cap can be a sign of a bad cap?

when i get home i was going to run it with the cap off & look for bubbles & i will try the cap off my other bike.

the last time i rode it, i did not notice any running issues. i also had a look at the overflow tank near the end of the ride & do not recall it being full. the bike sat for almost 2 weeks after that ride.

any input appreciated, but i think pulling the cylinder is in my future.

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With a cold engine, remove the cap, is the radiator full, does it look like oil/smell like exhaust? If yes, then it is a gasket. If no, then it means that the radiator is no sucking the overflow back in on cool down. Could be just the hose between the overflow tank or a bad cap then.

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Bad cap would release pressure, not hold/build it.

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With a cold engine, remove the cap, is the radiator full, does it look like oil/smell like exhaust? If yes, then it is a gasket. If no, then it means that the radiator is no sucking the overflow back in on cool down. Could be just the hose between the overflow tank or a bad cap then.

when i removed the cap last night, the coolant level in the tank seemed just low enough to account for the overfull overflow.

i'll have a better look at it today. i'll get a good look at all the lines too.

thanks for the input.

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head gasket diagnosis is easy. look for the water in your oil.

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from what i understand, a bad head gasket does not always lead to coolant in the oil.

i will check the oil for water contamination tonight though.

yeah, i'm pretty sure it's a bad head gasket, but was hoping for something less serious of course. guess i started this thread hoping for a simple answer.

and as mentioned, i did not have time to mess with it last night.

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from what i understand, a bad head gasket does not always lead to coolant in the oil.

You are correct. If it's a teeny little leak that only occurs at high temperatures, the leak will be one way.

But it may still be something else. More investigation is required. 👍

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I had a similar problem on an rmz450. No water in the oil, and no discoloration of the coolant either. Bike would sit over night and in the morning rads were still pressurized. I would lose a small amount of coolant each ride. It was a leaking head gasket.

Make sure the head isn't warped and use oem gaskets if it turns out to be the head gasket.

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I can't see how a leaky head gasket would allow a cooling system to hold pressure. The pressure would bleed off almost immediately through the leak when the bike is not running.

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the 470 in my E/SM unfortunately.

unfortunately it will always be like this till you get the right cams.

even the stg 2 hotcams dont bleed off enough cylinder pressure.

even with the compression lowered like it is its a gamble.

you can try adding 2 more base gaskets but i dont think the cam chain is long enough.

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from what i understand, a bad head gasket does not always lead to coolant in the oil.

i will check the oil for water contamination tonight though.

yeah, i'm pretty sure it's a bad head gasket, but was hoping for something less serious of course. guess i started this thread hoping for a simple answer.

and as mentioned, i did not have time to mess with it last night.

Ahh, i didn't know that. The ones i have seen have always had contamination. Good luck, i hope you get it sorted out soon!👍

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Eddie, I'd think that when the engine cooled off, it would sucjk the coolant back in though.

the rads are under pressure still even after it cools off.

14psi will keep the coolant from coming back.its not the same thing as the coolant just expanding when hot.

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unfortunately it will always be like this till you get the right cams.

even the stg 2 hotcams dont bleed off enough cylinder pressure.

even with the compression lowered like it is its a gamble.

you can try adding 2 more base gaskets but i dont think the cam chain is long enough.

i added a little coolant to the rads yesterday & ran it with the cap off.

yep, it was bubbleiscious. lots of bubbling going on. i had the coolant level just above the coils & fluid was bubbling out of the fill hole.

the only other thing i did was removed the overflow line from the catch tank, opened the rad cap & blew thru the line - it was clear...and a pointless test at the time.

thinking back on my last ride, i may have seen 9500 rpm on my tach a time or two.

eddie

1st of all - if i add extra base gaskets, are you referring to 2 more 3 layer gaskets, or 2 single layer gaskets?

if so, i think you're going to be right about the chain being too short. i know snapping the cams in now as it is isn't exactly easy & mcct is pretty far out, if not all the way out.

2nd - if i were to upgrade to rhc cams, wouldn't i need o/s intake valves, rhc springs & porting? and obviously cams would need to be degreed.

not sure if you remember, but i went with rhc valves & oem springs for the rebuild.

3rd - i think i need to pm you for some quotes

thanks for everyones replies

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sorry about your headgasket REHH its always sad when a bike goes down....at least in your case you have a spare DRZ

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