CBR600 ? Oil in the coolant system

[Serendipity]

Oh, buggeration!

Second bike out of action in a week! I came back to my ’94 CBR600 the other day to discover a small patch of light brown oily water on the ground under the left side of the bike. Damn, I thought, water and oil mix never good, so I set about finding where it’s coming from.

Stripped off the plastics and degreased the engine. Then warmed the motor and watched for drips……… nothing, nada.

So I switched it off and immediately drip, drip, drip from one of the breather pipes. I followed it back to the coolant expansion tank to find it full to the brim of the nasty brown gunk.

The obvious conclusion is a failure point between the water jacket and the oil system, presumably at a weak point like the head gasket or something. The oil in the sump seems uncontaminated so again I presume that where it’s failed the oil is under higher pressure than the water so oil is being forced into the cooling system, but not the other way around.

Anyone got any experience of where these leaks normally occur? I suppose the fix will include tracking down where the leak is happening and sealing that. Then probably both the oil and cooling system will need flushing to get rid of foreign substances.

I was planning on putting the bike in the workshop for valve clearances and carb balancing, two of the tasks I normally leave to the pros so I wonder if it’s worth getting them to take the head off and see if it’s the gasket that’s failed. Could be pricey.

What does anyone else think?
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Kickstart]

Hi

Probably the head gasket, but another possibility is the seal on the back of the water pump. Head gasket will probably pressurise the cooling system though.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Paddy Blake]

The O ring

[Kickstart]

Hi

No idea if the above is correct, but sound entirely possible and for the cost of a few O rings it is certainly the first thing to check.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Serendipity]

Indeed, I will investigate this possibility in the first instance. Definitely a much simpler fix, although I bet I have to remove the downpipes to get the oil cooler cover off and that's gonna be a royal pain because I fitted stainless ones about six years ago and haven't touched em since. The bolts will be seized solid!

Trouble is they’re gonna have to come off no matter what. Definitely one for “jobs I hate” thread.

Somehow I suspect the CBR is coming off the road for the foreseeable future while I get my hands thoroughly dirty and loose a fair amount of knuckle skin.

Now I just need to finish rebuilding the RXS engine so I can have some two wheeled transport that doesn’t require peddling.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Paddy Blake]

You will need to pm me or email as i have had enough of idiots acking up.

Paddy.

[Serendipity]

Thanks Paddy and Keith for the good suggestions. My current plan of action is to drain all the fluids and replace the o rings and seals on the oil cooler.

I will also look at servicing the water pump in case that’s the problem. Having checked it looks like the pump is a non serviceable sealed unit (according to Haynes anyway) and you can’t buy the seals separately. The pump is still standard fitment on the Hornet and CBF600 so I’m hoping it’s not too pricey.

Do you know a good method for flushing oil residue out of the water system? Or does it not really matter? A couple of runs through with fresh water before filling with coolant could do the job.

Incidentally to remove the oil cooler it looks like I can get away with leaving the rad and downpipes in place, although it will make the job a bit fiddley so I may whip em off anyhow. I would definitely have to remove a PAIR system, but it’s not fitted to mine (California models only I believe).
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Paddy Blake]

The oil cant get into the coolent by the water pump.

[Serendipity]

[Walloper]

You can buy cooling system cleaners that remove oil deposits.
Though a cup of washing Soda in solution added to the system will break it up just as well.
Mix the soda in warm water and add when it's clear. Helps prevent blockages.
Expect to have to do this two or three times before all the oil is gone. And then flush with gallons of cold water from the bottom up.

Remember that until you add antifreeze you will not be protected from frost............

Also think about changing the oil and filter. Some filter elements can soak up the water and be blocked off. Water in the oil prevents the oil doing its job in hot places. Same effect as no oil.

Water CAN get into the oil.
When you shut off the engine the cooling system maintains pressure whilst the lube system almost instantly drops to zero.
The water at higher pressure can then seep through porous coolers etc.
But you may not notice emulsified oil as 'osmosis' lets antifreeze through before water.
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair