Question about 2003 Yamaha YZ 250

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2003 yz impeller seal is leaking, do i need to replaice head gaskets thanks ian

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I am not sure what you mean by impeller seal so here are a few scenarios:

**Note: Based on YZ250. others may be similar.

-If the gasket around the impeller housing is leaking you can replace that on its own. Open rad cap, drain the coolant using the lower screw with the copper washer behind it. Then remove the other 3 bolts, remove cover, clean mating surface, install new gasket, snug everything up, and replace the coolant.

You don't need to replace the head gaskets unless your leaking from there, or getting coolant in the engine.

The same would apply to your base gasket.

just in case:

-if your transmission/gear oil is milky, your will have to change the oil seals on the impeller shaft.

Posted on Jul 31, 2009


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Coolant is leaking from weep hole. I replaced both oil seals, gaskets (case and water pump) impeller shaft and bearings. Only thing I didnt replace was the impeller itself.

Hi, Anonymous for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
coolant leak leaking weep hole 05 yz250 Yamaha 2 Stroke
2000 yz 250 coolant leak
YAMAHA YZ250 LC Owner Service Manual
OEM parts for Yamaha

Sep 22, 2013 | 2003 Yamaha YZ 250

1 Answer

I have a Yamaha yz 125 2003 and there is water leaking out the bottom through a small whole and was wondering why it is doing that as it has just started doing it recently

This is telling you your oil and water seal need replacing ASAP do not ride until fixed as you will seize bottom end guaranteed !
there is small seal each side of your water pump impeller when you take the impeller out replace both even if only one needs doing as you will be going back to replace the one left soon after as they always go together..
Most people would not do this repair without replacing the impeller as well - usually the impeller starts to wear groves where it spins inside the seals then damages the seals So you get the theory behind replacing the whole lot as old impeller can damage your new seals
The seep hole is designed to give you warning of burst seal before its way to late as without the seep hole leak you would have no idea you are leaking coolant into the motor
You can do your self its a bit of work but not complicated - if you do your self don't forget to change your engine oil couple of times after first few rides reduce any risk of having coolant inside it where it should not be
good luck regards Jamie

Aug 29, 2011 | 2003 Yamaha YZ 125

3 Answers

2004 YZ 250 is leaking fluid out of the hole just behind water pump underneath the crankcase. The gasket looks fine and its not leaking from the gasket its actually coming out of the hole. I started...

The hole is a weep hole, designed to drain coolant from water pump seal leakage or oil from bearing seal leakage from contaminating either system. So one of the seals is leaking, and you should rebuild the pump.
Looking at the parts diagram it appears the impeller is threaded onto the shaft on the YZ250....hope that helps, heres the parts diagram

Mar 06, 2011 | 2004 Yamaha YZ 250

1 Answer

Engine problem

Water coming out of the hole is to indicate that the pump seals need to be replaced. Some water is probably in the gearbox now. If the oil is whiteish you do. Pull the right case cover then remove the pump cover and the impeller then replace the seals. Remove the liquid gasket so that the hole is open again. You can see a parts diagram at Click on the red "OEM PARTS" tab. Items 6 and 7 are the seals separating the water from the oil. Put a wrench on the impeller shaft next to the gear, then unscrew the impeller as if it were a screw. It would be good to replace the gasket (item 10) as well. Please take a moment and rate my answer to your problem.

Jan 03, 2010 | 2003 Yamaha YZ 125

1 Answer

05 yz250f milky oil

milky oil is water mixed into the oil. Replacing the seals should fix the leak. Nothing special on the top end gasket.

Sep 26, 2009 | 2004 Yamaha YZ 250 F

1 Answer

2000 yz125 - Water pump seal change

The two seals in the diagram below are separated by the casing they fit into. The impeller is threaded to screw onto the impeller shaft. I think you already knew that by your "holding the tire" note. The center casing does not get split. The right casing does remove then a wrench is used on the shaft as the impeller unscrews counter clockwise. It is risky to "Lock the wheel" because the gear on the impeller is very thin and can break.

A “very helpful” rating on this answer? Thanks!


Jul 01, 2009 | 2003 Yamaha YZ 125

1 Answer


The impeller screws onto the impeller shaft. Go to the site below and you can see a parts diagram. You will select the brand, year, model, etc... It has the part numbers and prices.

There are actually two seals. Are you sure the leak is a bad seal and not the water pump gasket or a cracked/broken housing cover?

Please post a top rating for this solution. Thanks! :)

May 19, 2009 | 2004 Yamaha YZ 125

1 Answer

Getting water in the crank case

if i had to guess at this one the seal behind the impeller on the water pump is bad

Apr 11, 2009 | 2003 Yamaha YZ 450 F

1 Answer

Water leak/mixing with oil

change the seal behind the water pump impeller
the shifter shaft seal will stop leaking
if it continues to mix water and oil you will have to change the head gasket

Mar 10, 2009 | 2002 Yamaha YZ 426 F

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