DT125X cooling problem

[SouthWalesYammy]

Hi everyone,

Right so I’ve done a top end rebuild of the engine and the engine runs sweet. Running it in as I go to make sure it works properly.

However, I’ve come into a problem.

The coolant system keeps emptying itself. It first started with a bit of a leak from the top of the radiator near the cap, but then the majority of it ended over the rear tyre so seemed like it was something to do with the overflow/expansion.

I replaced both the thermostat and radiator cap, then refilled with coolant. This seemed to fix the problem but then found the system to have let a load out again over the rear of the bike (no longer any from the radiator cap).

My thinking is it is something to do with the expansion/overflow bottle. Any ideas?

Also, I was using a putoline coolant, any other recommendations?

Thanks in advance

[oldman]

Head gasket leak

[shellatit]

If you have used genuine gaskets and it still does it I would say the head is possibly warped

[SouthWalesYammy]

@oldman said in DT125X cooling problem:

Head gasket leak

Would this cause the coolant to end up over the rear tyre, it’s right below where the overflow bottle is. That’s what makes me think it’s that

[oldman]

Yes. System overpressurises with combustion gases forcing fluid to escape to expansion tank
Did tank have liquid level prior to problem? Would overflow with excess coolant

[SouthWalesYammy]

@oldman

Ahh okay, do you think I’d be better off checking some other things first (the hoses attached to the expansion bottle, the diaphragm and cap) before taking the head off?

[DTR+NSR]

@SouthWalesYammy is the area where the rad cap seals agains't sound? I had exactly same symtoms and in end traced it to corosion damage where the rad cap seal, seals against.

[SouthWalesYammy]

@DTR-NSR

Are you talking about on the inside of the opening on the radiator? Or on the estimator cap itself?

[DTR+NSR]

@SouthWalesYammy inside the opening on the radiator. There's a slight raised ridge the rubber seal on the rad cap seals agains't. If the system can't pressurise there, the coolant will expand as it warms and flow straight to the over flow bottle.

[oldman]

Considering you have just done a top end rebuild and the problem started my money's on the head gasket. Easy to sort a warped head (if that's what it is) there's a tutorial on here somewhere. Or did you use a cheap gasket?

[SouthWalesYammy]

@DTR-NSR

I’ll check this Saturday when I get out to look at the bike, thank you!

[SouthWalesYammy]

@oldman

Hopefully it’s not this, I’m going to check everything else first then this’ll be my last call

[Walney-Reptiles]

Id also go with the head gasket, happened many times with me until i skimmed my head with a glass mirror and wet n dry sand paper

[declan]

@SouthWalesYammy I had the same problem mine fixed it’s self) EDIT) the only thing to do with cooling i changed was the radiator cap maybe that was the issue?