CBR 600F2 1991 - 1994 CBR 600F2

Oil Cooler Seals or Head Gasket?

Old 06-10-2014, 08:55 PM
Registered Users
Thread Starter
Join Date: Mar 2014
Posts: 5
Default Oil Cooler Seals or Head Gasket?

I have been reading a lot of threads about diagnosing over heating issues and just wanted to get some thoughts on this one... i am almost certain the head gasket is blown based on the following:

My 93 F2 was running really hot last riding season and this year I decided to do a little investigating before getting it back on the street. The cap, & thermostat are new and check good. The water pump is checked and there is no leak over between the coolant and motor oil at the pump. I put a pressure test gauge on the radiator and pressurized the system to 14lbs and the gauge did not move for 10 minuted until I finally released the pressure....

NOW, here is the diagnostic I think tells me its a head gasket.

After all these checks I thought there may be air in the system from checking the water pump and changing the thermostat so I put one of those cooling system burping funnels on the radiator opening. For those of you who are not familiar, this is a big funnel that locks into the radiator hole where the cap goes and it seats down deep enough into the radiator that is seals off the over flow hole to the expansion tank so no air can get into the radiator or coolant can escape from anywhere but the funnel...


What I noticed after about 5-10 minutes of running the motor and the thermostat opening up; air was STILL coming up out of the radiator and I could never get the air to clear out. Then I noticed a film of oil residue start to form around the inside of the funnel wall and the bubbles that were coming up from the radiator were also "oily" and whenever I would hit the throttle hard, I would get a surge of bubbles come up into the burp funnel...

I have seen people talk about the oil cooler o-rings causing oil to get into the coolant, but Im not sure how that would cause air to get into the cooling system... My diagnosis is that the head gasket is blown and leaking emissions (air) into the cooling system..

Old 06-11-2014, 08:35 AM
JNSRacing's Avatar
Welcome Crew and ROTY 2014
Join Date: Dec 2010
Location: Kansas
Posts: 2,059

It's not easy to get the cooling system 100% free of any air, and even with that special tool, it might take 15 minutes or more - you're not going to be in bad shape, if you've got just a little bit of air.

On the oil in the coolant, the easiest, and thankfully, most common place for this to occur is indeed at the oil cooler, due to one or more seals failing, but the best way to check your head gasket is to do a compression/leak-down test.
Just out of curiosity, do you have coolant in your oil as well?

It would be worth it to try the oil cooler angle first, as you can score all the O-Rings/gaskets for that job, for $20 to $30 - then put in new coolant, and change the oil if it's contaminated, and run it again.
Old 06-11-2014, 11:14 AM
Registered Users
Thread Starter
Join Date: Mar 2014
Posts: 5

As for your question about coolant in the oil, it does not appear so at this time. I have not actually drained the oil from the bike, but the dip stick looks clean. I have not dumped the oil yet since I need it to run the bike for tests ... But it will get an oil change before she goes back on the street.

I agree that the oil cooler O-rings should not be ruled out. It makes sense that oil would bleed into the coolant (or vice-versa) and that the air bubbles may be from remaining in the system, but I want to be thorough in my diagnosis and make sure Im attacking the problem and not throwing parts at it. The leak down test would make sense and would not be a problem. I have access to a leak down tester, so that will indeed be on the top of the project list this weekend.

My thoughts (and I would appreciate feedback); is that if the leak down test shows a cylinder (or two) is indeed leaking down, AND I run an air test on the radiator opening and detect exhaust emissions in the air bubbles that are coming up through the radiator, then that would indeed be a 99.9% diagnosis of a head gasket, correct?? Other than a cracked block or head, I dont know what else would cause that. I dont think oil cooler o-rings would put air emissions into the cooling system would it? Or cause a compression loss?... I realize a bad valve seat could also cause a leak down, but if that is the problem, the head needs to come off regardless.. lol

I agree that the O-rings may be the cause based on the diagnosis to date, but with an emissions test and a compression leak down check, that would pretty much move the finger over to the head, yes?...

I will have more diagnosis data Saturday...
Old 06-11-2014, 11:49 AM
gtcole's Avatar
Welcome Crew
Join Date: Feb 2013
Location: Waycross, Ga
Posts: 688

In my experience you are correct in your assumption. If a leak down test comes back bad, doesn't have to be for two cylinders, and mainly the emissions test is fail, then yes. I would say replace the head gasket. Like previously stated, a little air is normal. And the oil cooler will cause oil in the coolant. So don't rule that out as far as your leak goes. In my opinion, if it turns out to be a head gasket, do the oil cooler too. Better once then twice.
Old 06-11-2014, 04:39 PM
Registered Users
Thread Starter
Join Date: Mar 2014
Posts: 5

Agreed... So the oil cooler looks to be the two O-rings for the coolant passages and the main seal o-ring for the cover??.... Changing the head gasket would only require a new valve cover gasket and the head gasket itself, correct?
Old 06-13-2014, 07:31 AM
gtcole's Avatar
Welcome Crew
Join Date: Feb 2013
Location: Waycross, Ga
Posts: 688

Provided everything is in good condition, you could get away with just the head gasket. The valve cover gasket is rubber. So as long add it's not leaking, compressed, dry rotted, or deformed, etc, you could reuse it. Otherwise, yes you are correct valve cover and head gasket.
Related Topics
Thread Starter
Last Post
F4i - Main Forum
04-22-2009 10:20 PM
CBR 600F
10-04-2008 10:52 PM
1000 Modifications
08-07-2007 12:51 AM
General Tech
01-17-2007 06:13 PM
CBR 600F3
03-06-2006 03:51 AM

Thread Tools
Search this Thread
Quick Reply: Oil Cooler Seals or Head Gasket?

Featured Sponsors
Vendor Directory

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.