I have a 2004 YFZ450 and it tends to slowly leak coolant when riding. From what I can tell the coolant is leaking from the engine gasket. After a day of riding the coolant level tends to go from the FULL line to the LOW line. (I obviously never let it get too low.) I mostly do trail riding. Although I do ride aggressive, I certainly am not

Is this normal for a sport quad?
If not is there any simple fix or do I have to have the engine gasket replaced? (BTW the engine has never previously been taken apart.)

Thanks for any help/suggestions.

 

It shouldnt leak it sounds like you have a bad gasket. I rode mine hard for a year and the coolant level hasnt moved.

 

Thanks for the feedback. That is what I expected.

 

See if some of the coolant is ending up in your oil. You can cause major engine damage if you allow the coolant to thin out your oil too much.

 

is your gasket worn out or damaged?

 

Check your water pump seal. . . I'd put money on this being the issue!!!

There is a weap-hole that is under the cases. . . Not sure where on the YFZ. Fix it now.

The O-ring can be bought from the dealer for about $7 or open it up and take the O-ring to your local Napa Autoparts store. It is a standard oil-seal type O-Ring.

Are you running coolant or just water for cooling?

Check your oil. . . if it has a milky appearance than you need to drain and flush it out.

 

Thanks everyone for the feedback; I greatly appreciate it. I figured it wasn't normal, but just thought I would check.

I am planning to have the main gasket replaced as that appears to be where it is leaking from.

Thanks again.
Josh

 

BTW DuneMe... I am running only straight coolant and my oil does not appear to be milky.
However, I haven't heard anyone suggest the water pump. Why would the water pump be causing coolant to leak out?

Thanks,
Josh

 

The water-pump saft goes from the engine (oil side) through the oil-seal to a gap (weap hole) to another oil-seal (in this case it is holding back coolant) to the impeller that moves the water/coolant.

If you run straight water, there isn't sufficient lubricity in the cooling side and the oil-seal (that's what they call these kinds of gaskets/seals) will fail. The seal looks like about 5 washers thick. . . it is kind of a "C" shape with a spring inside the "C" to keep the seal on the rotating shaft.

Straight coolant isn't a good idea. . . hopefully you meant a 50/50 mix? Straight water will give you better cooling as the glycol in "Coolant" has LESS heat transfer ability than water. Coolant is used to protect your system from two things. . . freeze and rust. When you add glycol to water you lower the temperature at which it will freeze. There are also rust inhibitors in coolant. . . not much of an issue in these engines really as there isn't much or any steel in contact with the coolant.

You say "Main Gaskett"??? Do you mean the Head Gasket? Do you see it coming out of the head gasket?

Another thought. . . a bud with a YFZ had a water-pump seal go and didn't know it. . . once he replaced the seal he found the Head Gasket now leaked (probably due to excessive heat because he didn't have coolant in it.)

If you think it is the head gasket, I would replace the water-pump seal while you are doing the work. Hate to see you run into the same problem again because you didn't end-up fixing what was really causing the problem.

Let us know how it goes.

 

Thanks DuneMe. That's good information (most of which I was not aware of).

The leaking "appears" to be coming from the Head Gasket at the bottom of the engine block. But I will definitely replace the pump seal as well upon your good suggestion.

Thanks much, and when I tear it apart in 2 weeks I'll be sure to post a message as to if it fixed it.