Blown head gasket, has anyone done a thread on replacing one? - Wrist Twisters
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post #1 of 20 Old 06-27-2019, 04:32 PM Thread Starter
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Blown head gasket, has anyone done a thread on replacing one?

Looks like a small oil leak from the bottom of the head gasket. I don't know the cause, but for the first time ever, the coolant reservoir was empty. I topped the reservoir off and a lower hose leaked out the overflow.

Topped off the oil with 1 qt. This is the first time ever that she lost any oil.

So I'm going to start doing the research on what I need to replace the head gasket.

I'd like to do a leak down test and I assume the head should be resurfaced. The gasket is about $60 and a gasket kit seems to be just over $100.

She's at 38,000 miles now, so the valve check/adjust will happen.

Questions are about what all I should get into. Cam chain tensioner etc?

I know that some have written up on the throttle cable and how to remove the air box, but don't remember seeing any full head gasket job.

I'm assuming the engine can stay mounted while the head is removed, but is it worth it to keep it mounted?

It's a stressed member of the frame, and I don't know how to replace one that is stressed, never done that type of engine before.

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post #2 of 20 Old 06-27-2019, 10:19 PM
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This doesn't seem to happen much to the 919. There's a few threads on this subject on other bike forums. Similar engine, the cbr900. That bike has been around for longer and possibly gets more of a beating.
There's also a pretty good write up on head removal/installation in the workshop manual. It can be done with the engine still in the bike.
I wonder if it would be worth sending the head off to a good shop to have that gone over while it's off?
Other than having Waaay to much fun on your bike recently I wonder what's caused a possible blown gasket or worse a cracked head. Any crazy temp fluctuations recently?
So your losing oil and coolant? And neither is ending up in the other? And neither system is showing signs of excessive pressure? Has your exhaust changed? Have you pulled your plugs and checked them out? Too many questions?
The leak down test is good and pretty much the first step in the workshop manual so your on the right track there.

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post #3 of 20 Old 06-27-2019, 11:51 PM Thread Starter
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Quote:
Originally Posted by Islandboy View Post
This doesn't seem to happen much to the 919. There's a few threads on this subject on other bike forums. Similar engine, the cbr900. That bike has been around for longer and possibly gets more of a beating.
There's also a pretty good write up on head removal/installation in the workshop manual. It can be done with the engine still in the bike.
I wonder if it would be worth sending the head off to a good shop to have that gone over while it's off?
Other than having Waaay to much fun on your bike recently I wonder what's caused a possible blown gasket or worse a cracked head. Any crazy temp fluctuations recently?
So your losing oil and coolant? And neither is ending up in the other? And neither system is showing signs of excessive pressure? Has your exhaust changed? Have you pulled your plugs and checked them out? Too many questions?
The leak down test is good and pretty much the first step in the workshop manual so your on the right track there.
I rode tonight and she seems fine, so I don't think they are mixing. At least, I don't think the water is getting into the oil.

I've ridden in 100+ temps, but didn't notice any problems at all. I'm thinking she got too hot at some point and warped the head. I'm going to keep a close eye on things, but I did see oil coming from the head gasket and warping is the only thing I can think of. Maybe there's o rings in there like my other bike and maybe one gave way.

I'll have to drain the oil and check for water, but the site glass looked good.

I should pick up some honda oil and coolant, then drain and examine both of them to see if they've mixed.

I'll search for the CBR900 forums and see what I can find. Hopefully, it's pretty straight forward.

It's very strange that this is happening as the 919 is not known for this. I'm sure I'm not the only one in 100+ temp that's pushed this engine.

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post #4 of 20 Old 06-28-2019, 04:51 PM
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Quote:
Originally Posted by KarlJay View Post

1
Looks like a small oil leak from the bottom of the head gasket. I don't know the cause, but for the first time ever, the coolant reservoir was empty. I topped the reservoir off and a lower hose leaked out the overflow.

2
Topped off the oil with 1 qt. This is the first time ever that she lost any oil.

3
So I'm going to start doing the research on what I need to replace the head gasket.

4
I'd like to do a leak down test and I assume the head should be resurfaced. The gasket is about $60 and a gasket kit seems to be just over $100.

5
She's at 38,000 miles now, so the valve check/adjust will happen.

6
Questions are about what all I should get into. Cam chain tensioner etc?

7
I know that some have written up on the throttle cable and how to remove the air box, but don't remember seeing any full head gasket job.

8
I'm assuming the engine can stay mounted while the head is removed, but is it worth it to keep it mounted?

It's a stressed member of the frame, and I don't know how to replace one that is stressed, never done that type of engine before.
1
Is the leak a sweat/ooze or a leak that dribbles?
Is it on the right side as you side on the bike?
Keep in mind that the oil feel to the head is a single feed from the block upwards right beside the chain drive cavity.

2
Have all the oil level checks been consistent, and based on both wheels on the ground and bike balanced nicely?
(thus begging the obvious question about the practicality of doing oil level checks in general LoL ?)

3
The factory service manual is pretty good.

4
While Leak Down Tests can reveal much, IF you only have a gasket failure at the oil feed to the head, a L D T will not be helpful.
Don't surface the head unless it is out of plane and/or damaged.

5
Good.

6
Cam chain tensioner should not be an issue.

7
I think you are right, but at least the factory service manual is good.

8
Yes it can.
Why take it out if you don't have to.
The 919 engine is not fully stressed member, just partially.
It should be an easy in/out operation but force more scope of work that is not necessary and offers zero benefit.

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post #5 of 20 Old 06-28-2019, 05:35 PM
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Leak Down Testing

Quote:
Originally Posted by KarlJay View Post

I'd like to do a leak down test
Keep in mind that common Leak Down Testers with 0.040 in. diameter orifices, give bogus results on small engines.

So far, I've only heard of one standards agency that has a governing specification.
It's the FAA, and the 0.40 in. diameter orifice is for engines up to 1,000 cubic inches (16 litres), and the supply pressure is to be 80 psi.

Therefore, whacking a 1/16th the limit sized engine with the typical 100 psi fed L' D' T' with 40 thou' orifice can only give extremely misleading % leakage values.

My guess is that seriously good car and motorcycle engine masters use smaller orifices, and have years of experience to tell them what the values they get, truly mean for the particulars of the engine they are testing.
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post #6 of 20 Old 06-28-2019, 06:10 PM
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I'd be looking for other sources for that oil leak. You just never hear of these bikes blowing head gaskets. That's not to say it can't/hasn't happened.
The rubber head cover gaskets have been known to leak. The one on my bike leaked, left hand corner. Cause the oil was clean it ran down and gathered elsewhere. You couldn't actually see the leak.
Do these bikes have spark plug drain holes? A leak from the gasket here could manifest elsewhere.
Also my bike never maintains the full coolant level in the overflow bottle. If I fill that overflow bottle to the line my bike will suck it up and spit it out.
Could excessive crankcase pressure force oil past head gasket?
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post #7 of 20 Old 06-28-2019, 10:37 PM Thread Starter
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The leak is on the left side as you sit on the bike. It seems to leak at the bottom of the head gasket, but I'll have to clean everything off and check several times again.

I did and oil change today and didn't find any water in the oil, so now I got to find out where the water in the reservoir went. After I topped off the reservoir, water drained from that tube at the bottom for the bike, so I assume it was topped off, but will check by removing the tank.

She actually rode very nice after the oil change, so if the leak doesn't get worse, I'll be able to ride for a while, this will allow me to get all the parts / tools that I might need.

As far as the leak down goes, one of the better parts of the test is just listening for where the air is passing. I did this on another bike and could hear air coming out the exhaust and a small amount coming out the intake. It's more the chamber holding air or not. I have to find where my adapter is, haven't seen it in a few years.

If the gasket is just leaking oil, that's one thing, it may have just lost the seal where oil passes and it could be just an oil return as it doesn't seem to have any real pressure to it.

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post #8 of 20 Old 06-28-2019, 10:43 PM
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Can you post a pic of exactly where you think it might be leaking from?

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post #9 of 20 Old 06-29-2019, 08:30 AM
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Such a small leak as described, coincident with an engine understood to not be burning oil, is inconsistent with the need of a 1 qt top up.
So, something in the present equation is wrong.

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post #10 of 20 Old 06-29-2019, 08:57 AM Thread Starter
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Quote:
Originally Posted by mcromo44 View Post
Such a small leak as described, coincident with an engine understood to not be burning oil, is inconsistent with the need of a 1 qt top up.
So, something in the present equation is wrong.
Interesting point, I was thinking that 1qt is a LOT from that little seep that made a 3" dot on my driveway. A 3" dot on the driveway could be done with a very small amount of oil.

I did notice the stains near the starter where the oil had been leaking for a while and seemed to burn off or dry up.

Still, 1qt of oil is a LOT to lose.

Maybe it's being burned out the exhaust.

There's still the issue of what happened to the water.

Generally, you'd guess it was being sucked in during a vacuum, then burned out the exhaust.

Both of these can happen because of a warped head, but these engines aren't known for being that sensitive to heat.

I'm sure I'm not the only one to ride in 100+ temps.

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post #11 of 20 Old 06-29-2019, 09:11 AM
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Quote:
Originally Posted by KarlJay View Post
Interesting point, I was thinking that 1qt is a LOT from that little seep that made a 3" dot on my driveway. A 3" dot on the driveway could be done with a very small amount of oil.

I did notice the stains near the starter where the oil had been leaking for a while and seemed to burn off or dry up.

Still, 1qt of oil is a LOT to lose.

Maybe it's being burned out the exhaust.

There's still the issue of what happened to the water.

Generally, you'd guess it was being sucked in during a vacuum, then burned out the exhaust.

Both of these can happen because of a warped head, but these engines aren't known for being that sensitive to heat.

I'm sure I'm not the only one to ride in 100+ temps.

I think it's still premature to associate the coolant loss with the oil.

As for the head warpage, while that may be a theoretical possibility, it is a highly unlikely one that can't be confirmed without removing the head.

As for the oil burning, two points arise from that proposition.
What would make engine go from no burn to heavy burn like a switch has been flipped, but still run nicely?
What is the present manifestation of the heavy burn rate?

What you are seeing is sick feeling tummy stuff, but I have a gut feeling it's not as bad as you're presently thinking it might be.

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post #12 of 20 Old 06-29-2019, 09:54 AM
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Another thought.
It is impossible for there to be a oil pressure based leak at the left side, as there is no pressurized oil zone between the head and the block anywhere near that position.
And likely impossible for a migratory leak all the way across the deck from the right side, which is where the pressurized feed to the top of the head resides.

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post #13 of 20 Old 06-29-2019, 12:02 PM Thread Starter
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Quote:
Originally Posted by mcromo44 View Post
Another thought.
It is impossible for there to be a oil pressure based leak at the left side, as there is no pressurized oil zone between the head and the block anywhere near that position.
And likely impossible for a migratory leak all the way across the deck from the right side, which is where the pressurized feed to the top of the head resides.
Interesting, I wonder if the leak starts at the right but ends up at the left because of the bike being on the side stand.

IIRC, it was pretty even across the line, so it could have traveled down the outside of the gasket. I'll have to get in there and have a closer look before I start tearing into things.

Any ideas about where the water could be going?

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post #14 of 20 Old 06-29-2019, 01:50 PM
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Quote:
Originally Posted by KarlJay View Post
Interesting, I wonder if the leak starts at the right but ends up at the left because of the bike being on the side stand.

IIRC, it was pretty even across the line, so it could have traveled down the outside of the gasket. I'll have to get in there and have a closer look before I start tearing into things.

Any ideas about where the water could be going?
I'd defer to Islandboy's post #6, noting it's his personal experience and not conjecture on my part.

By the way, have you changed your coolant recently?
That asked in terms of whether or not it was for sure fully purged of air.

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post #15 of 20 Old 06-29-2019, 04:48 PM
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KarlJay,
I've done a rather rudimentary search for 900RR/919 Hornet head gasket failures.
My guess is that you have done the same.
Aside from a turbo'd user who had to change head gaskets with some regularity, I have not been able to find one posted incident where the initial hunch/suspicion/ was actually confirmed and repaired by replacement.
I say that only to try to provide some comfort towards less angst, as the probability of a head gasket failure in a stock engine is extremely low and very much in the "car like" zone.
IF the engine had been over heated badly, to the point of engine damage also being likely, then that changes the probability.
But that is not your situation.
So, I think you can be more hopefully the final verdict is one that does not involve having to remove the head.

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post #16 of 20 Old 06-29-2019, 05:07 PM Thread Starter
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Quote:
Originally Posted by mcromo44 View Post
I'd defer to Islandboy's post #6, noting it's his personal experience and not conjecture on my part.

By the way, have you changed your coolant recently?
That asked in terms of whether or not it was for sure fully purged of air.
No, in fact, I'm not sure how to purge. I just checked the overflow and it was never empty before this.

I did a check just now and the oil is also on the right side at the head gasket AND there was something at the base of the coolant adapter that bolts to the head. I'm guessing that's where the Tstat goes. It didn't seem like oil but wasn't much there to go on, which if it's water/coolant, most would evap off, so I'll have keep an eye on that.

Maybe best to replace that one gasket at the Tstat/head and then learn how to purge the cooling system and keep an eye on it.

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post #17 of 20 Old 06-29-2019, 05:10 PM Thread Starter
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Quote:
Originally Posted by mcromo44 View Post
KarlJay,
I've done a rather rudimentary search for 900RR/919 Hornet head gasket failures.
My guess is that you have done the same.
Aside from a turbo'd user who had to change head gaskets with some regularity, I have not been able to find one posted incident where the initial hunch/suspicion/ was actually confirmed and repaired by replacement.
I say that only to try to provide some comfort towards less angst, as the probability of a head gasket failure in a stock engine is extremely low and very much in the "car like" zone.
IF the engine had been over heated badly, to the point of engine damage also being likely, then that changes the probability.
But that is not your situation.
So, I think you can be more hopefully the final verdict is one that does not involve having to remove the head.
There's enough of an oil leak where I can fully clean the surfaces and trace it down because it's on both left/right sides of the engine at the rear. I can't see any other source of an oil leak.

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post #18 of 20 Old 06-29-2019, 05:23 PM
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Quote:
Originally Posted by KarlJay View Post
No, in fact, I'm not sure how to purge. I just checked the overflow and it was never empty before this.

I did a check just now and the oil is also on the right side at the head gasket AND there was something at the base of the coolant adapter that bolts to the head. I'm guessing that's where the Tstat goes. It didn't seem like oil but wasn't much there to go on, which if it's water/coolant, most would evap off, so I'll have keep an eye on that.

Maybe best to replace that one gasket at the Tstat/head and then learn how to purge the cooling system and keep an eye on it.
Purging is pretty easy.
Engine cold.
Get tank lifted up.
Take off rad cap.
Start engine and let it warm up to point that thermostat starts to open - as evidenced by activity just below where the rad cap goes.
Watch the coolant level.
If it goes down, it means air was vented from the system so more coolant can be added.
Set the coolant level, then put the rad cap back on.
BE VERY CAREFUL NOT TO LET THE ENGINE RUN TOO LONG SUCH THAT THE COOLANT GETS MUCH HOTTER THAN THE 180 F OPENING POINT OF THE T'STAT.
The danger is getting scalded, badly.

True, there is a small air bleed hole in the thermostat, but it is not intended for doing major purges of air after a coolant replacement.

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post #19 of 20 Old 06-29-2019, 05:25 PM
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Quote:
Originally Posted by KarlJay View Post
There's enough of an oil leak where I can fully clean the surfaces and trace it down because it's on both left/right sides of the engine at the rear. I can't see any other source of an oil leak.
Any chance of a couple of pictures?

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post #20 of 20 Old 06-29-2019, 06:11 PM
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Make sure its not the rubber head cover gasket that is leaking oil.
Crankcase breather hose coming out of head cover intact/on.
I'm clutching at straws a bit cause I don't want it to be a blown head gasket.
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