Coolant Pressure Issue

Bike is a 1999 Honda VFR Interceptor.  Purchased it this summer while in Virginia.  Test rode it but never got to really ride it till we got back here and I could tag it.  The very first time I rode it, it overheated, got all the way up to 250.  It was a slow progression, took about 15 miles to get there in about 40mph traffic.  Parked it and trailered it home.  Looked on internet and saw lots of comments about how VFRs have an issue with running hot.  Something to do with the fact that the radiators (2 of them) are on the sides of the bike where they don�t get the best air flow, but obviously 250 is not just running a little hot.  



A bike mechanic relative told me to change the thermostat as he thought it sounded like the thermostat never opened.  So I changed the thermostat which was a total pain in the ass as it sits below the throttle body which has to be removed to get to it.  So I changed the thermostat and filled the bike with all new Honda 50/50 coolant.  Started the bike and just let it run.  It slowly got hotter till it hit about 218, then the fan came on and dropped the temp to 198 or so.  I then allowed the bike to do this one or two more times.  At this point I thought I was good.  NOPE!  About the second time I rode it, it got hot again, and the fan never came on.  So I talked to a bike mechanic who tells me bike thermostats almost never go bad, it�s probably the thermostatic switch which turns on the fan.  So I replace it, fill it back up with coolant.  Once again I�m good till about the second ride where it heats up again.  



So now I say screw it and take it to Metrictech in McKinney.  He puts it on dyno after filling the coolant just to see if the fan will come on, it does and he lets it cycle like 10 times.  He says he just thinks I had an air pocket in it.  Bike was good for one ride or so then it gets hot again, around 235 without the fan ever coming on.  So now I�m really pissed.  To make a long story short I ended up taking off the fairings so I could see the coolant system, hoses etc and the reservoir.  I mark the level of coolant in the reservoir, it�s at 1in deep.  I then take it on a ride.  As soon as I get on road (about 2 min) I gun it pretty hard, probably hitting 10,000rpm or so, I look down and the coolant has already raised up another inch or so in the reservoir, the bikes only been running for 3 or 4 minutes!?  



So I start wondering if it is only because of gunning the bike so hard.  So I take it easy for the next 10 miles, the reservoir level doesn�t change a bit.  So I gun it again, getting to 60mph as quick as possible, look down, sure enough, the coolant is up another inch or better.  So I go cruising down the highway first at 5,000rpm (about 70mph) for about 5 minutes, the reservoir level doesn�t change, then up to 6,000rmp (about 85mph), still it doesn�t change.  So now I know that what has been happening all along is that when I rev the bike real hard, the pressure is increased in the coolant system and coolant is sent to the reservoir, but this only happens when hitting 9,000 to 12,000rpm, or when gunning it from a stop where it may only be hitting 7,000 or 9,000, not totally sure.  



So mechanic tells me that hopefully it�s the radiator cap, if not it could be a head gasket or warped head allowing compression to leak over into coolant system.  I changed the radiator cap and this lowered the level a little, of how much coolant was moving from coolant system to reservoir, but it still was sending coolant over.  Now in talking with the mechanic and a few others, it sounds like it is unlikely that it is a head gasket or warped head, as, if this were the case, it would probably be producing so much compression, it would be blowing off hoses etc. Or I would be seeing an oil leak or oil in the coolant.  With the new radiator cap I was hitting the redline around 12-13,000rpm going from stop to 100mph in like first three gears; that�s a lot of frigging compression, I would think a head gasket or warped head issue that is allowing compression to leak into coolant system would have blown something up.  Instead it raised the reservoir level about � inch, maybe 1in.



Now to give a little history on the bike, the individual I purchased the bike from had laid the bike down on the right side, probably doing 5 to 10mph.  He said the mechanic replaced the fan and the right side radiator, the thing is, the bike has two radiators, one right one left, and only the left side has a fan attached.  But it is possible that he damaged the fan on the left side radiator and the right side radiator.  What I can say is that after I bought it and got it in the garage, I noticed over half the fasteners were missing.  I called the seller to ask him where they were and he said the mechanic said that any missing fasteners flew out when he dropped it. BULLHOCKEY.  Yea sure maybe the plastic fasteners, but where the cowlings are not broken, and the rubber/nuts are in place and not stripped, I don�t think so.  So anyhow it�s very possible the mechanic was a douche, or the seller, or both (most likely option).



I am about to pull my frigging hair out with this.  I do not want to get heads resurfaced if it is not needed.  I�m looking for anybody who might have any input on this.

Quote

So I talked to a bike mechanic who tells me bike thermostats almost never go bad, it�s probably the thermostatic switch which turns on the fan.
LOL. Never go bad. Usually the first problem, with these bikes. Seems you've done everything right. 100%. Have you burped it yet? (On the sidestand, is the way to go). Unless the polarity was screwed up, you really have covered all the bases, I can think of. Not to scare you,..........A head gasket is VERY RARE. But, it can happen, especially if the pervious owner, overheated it, numerous times. The only other ting I can think of is a bum new thermo. (I would figure that you would get a couple runs out of it, before having problems). For that fact, could be a bum cap, but that is much more rare than thermos.

Burp, go from there, is my only immediate advise.

My rad cap was failing to hold pressure, bike was overheating as a result and puking coolant out the reserve tank overflow.

Rad hoses were also soft at full Op. temp, not firm as they should be.


Try changing the rad cap, they're cheap.

Open the radiator (cold), run the bike on the side stand, and blip the throttle a few times. This is burping it to remove air.

Most likely causes I think would be an air bubble or faulty rad cap. Have you replaced the rad cap yet?

[image: View Post]veefer800canuck, on Nov 15 2007, 07:37 PM, said:

My rad cap was failing to hold pressure, bike was overheating as a result and puking coolant out the reserve tank overflow.

Rad hoses were also soft at full Op. temp, not firm as they should be.


Try changing the rad cap, they're cheap.

[image: View Post]jeremy556, on Nov 15 2007, 07:40 PM, said:

Most likely causes I think would be an air bubble or faulty rad cap. Have you replaced the rad cap yet?

LOL. Did you guys turn into me? Already replaced the cap. LOL.

Cheesh!! If she's been up to 250 and you didn't have warped heads beforehand, you may do now!! Sorry, don't mean to scare you out of your wits but, if you see it getting up over 125 while you're running your diagnostics and such, STOP THERE!! It's enough of an indication that it's not fixed.

I've seen a few cases of overheating on the VTEC, not somuch on the 5th gen, but in all those cases it was the "thermocontact", not the thermostat. The "thermocontact" as it's known in Spanish, (maybe fan switch in the Queen's English) is responsible for turning on the fan at a certain temp. Changing the thermostat was possibly a waste of time, but hey, now you have a new one!!

Try changing that part and see!! (Someone please mention how you call this thing in English, I've forgotten...   :unsure:

Good luck!!

(yeah, really smart idea not putting a fan on the right-hand radiator, surely they could be co-ordinated so as not to tax the battery too much by coming on at separate times (staged).

[image: View Post]Rivcyko, on Nov 15 2007, 07:51 PM, said:

[image: View Post]veefer800canuck, on Nov 15 2007, 07:37 PM, said:

My rad cap was failing to hold pressure, bike was overheating as a result and puking coolant out the reserve tank overflow.

Rad hoses were also soft at full Op. temp, not firm as they should be.


Try changing the rad cap, they're cheap.

[image: View Post]jeremy556, on Nov 15 2007, 07:40 PM, said:

Most likely causes I think would be an air bubble or faulty rad cap. Have you replaced the rad cap yet?

LOL. Did you guys turn into me? Already replaced the cap. LOL.
But he didn't say whether or not is was still overheating with the new rad cap, only that it was sending coolant to the overflow, which is normal.

Warped head?? check your compression first. if head is warped and getting pressure into coolant system 1 or more cyclinders will have a significant decrease in pressure with a compression check. Im not sure of the actual compression values but if 3 cylinders are say 160lbs and 1 is 130lbs. I would bet that is where your problem is. Doesnt have to have oil in the water to be a bad head. Do you get a lot of steam when you crank it up after it cools down out the exhaust.
Considering the bike is almost 10 yrs old I would also check the rads themselves maybe to be clogged. Just stick a water hose in one end of a rad  and compare the flow. try it several different ways.  if you get good flow with out much back pressure at the hose the rad should be good. try this on both sides in several different directions of flow. A good way to flush the system too. note if you see flakes or globes of material flowing out with the water. if so then that rad may be clogged. try something like CLR or drano to clean out the rad but be sure not to run it thru the motor.

Sounds to me like a blockage in the system somewhere, whether that be an air bubble or damage to the radiator.  But to clarify:

• These bikes only have one radiator fan, on the left-side.  When it activates it basically pulls air from the inside of the fairing and blows it out.  It's generally enough to keep the engine at around 110-114 celcius in traffic even on stinking hot days
  
• As the bike gets hot the water pressure increases.  The radiator cap spring allows the pressure to increase because higher pressure raises the boiling point to about 130 degrees celcius.  After that pressure is reached, the spring gives way and the extra volume of water goes into the overflow tank.
  
• Revving the engine when hot shouldn't cause the water level to rise in the overflow tank, unless there was a blockage in the system.

[image: Posted Image]
Coolant flow direction VFR800

Nete the direction of flow in the above diagram.  The water pump pushes water up to the right-side radiator just below the radiator cap and then it diverts to both radiators.  The cooler water is then fed back to the pump and pushed around the engine before then exiting up towards the right-side radiator again.  If there is a blockage in the system, there would be back-pressure which causes the water to be forced out the overflow tube.  This would be more noticeable at high revs because the pump is pushing more water.

Somewhere in your system, there is a blockage, most likely caused by air.  My preferred method of burping the cooling system (getting the air out of it), is the following:

• Start with a cold engine
  
• Remove radiator cap and start engine
  
• Bring up to operating temperature
  
• Watch the water flowing from the pipe into the top of the radiator (it will be just a trickle because the thermostat is closed)
  
• At about 76 degrees celcius the thermostat will open
  
• More water should now begin to flow into the radiator, and it is at this point that air will likely be seen.
  
• Let the system run like this until it reaches about 90 degrees celcius
  
• Optionally, let it get to 110 degrees celcius and confirm the fan comes on, and that the temperature drops or stabilises
  
• Stop the motor, replace the radiator cap and then go for a ride to see if it's fixed

Don't worry if some coolant spills onto the floor as it gets hot in there and the water level rises - you can always fill it up again!

Here's the thing, normally when fluid is moved to the reservoir, it's because the fluid has heated up and expanded therefore increasing the pressure so the fluid moves to the reservoir.  Then when it cools down, you end up with negative pressure so the fluid get sucked back in.  That is not the case with my bike.  The fluid moves to the reservoir right away, not after the bike heats up, but during the high rpm reving.  Basically the fluid is replaced with air.  That air is coming from somewhere.  The fluid never goes back to the coolant system.

Now I did do the burp thing as directed, twice.  One thing I did notice was that once the bike got to about 215f, the fluid level in the rad just plumetted, and the flow from the thermostat which seemed ample, was not enough.  It appeared as though the bike may have been getting some air in it due to this.  I also noticed that the bike temp dropped from 215f to 185f when this happened.  So a sudden drop in fluid level with a corresponding drop in temp.  Seemed strange to me.  The second time I did the burp thing, I had water at the ready to fill the rad when the level dropped again.

So anyhow with the system fully burped, it still pushed a bunch of fluid over to the reservoir when I reved it on the ride afterwards.  I'm almost positive that there is a small head gasket leak that is allowing the air from compression in the cylinder bleed over to the coolant system.  I can' t imagine where else this air could be coming from?

Time to compresion test. Hope I'm wrong. Someone smarter will chime in. The more you are narrowing, though,......eerrrrr.......

[image: View Post]kaldek, on Nov 15 2007, 09:32 PM, said:

Sounds to me like a blockage in the system somewhere, whether that be an air bubble or damage to the radiator.  But to clarify:

• These bikes only have one radiator fan, on the left-side.  When it activates it basically pulls air from the inside of the fairing and blows it out.  It's generally enough to keep the engine at around 110-114 celcius in traffic even on stinking hot days
  
• As the bike gets hot the water pressure increases.  The radiator cap spring allows the pressure to increase because higher pressure raises the boiling point to about 130 degrees celcius.  After that pressure is reached, the spring gives way and the extra volume of water goes into the overflow tank.
  
• Revving the engine when hot shouldn't cause the water level to rise in the overflow tank, unless there was a blockage in the system.

[image: Posted Image]
Coolant flow direction VFR800

Nete the direction of flow in the above diagram.  The water pump pushes water up to the right-side radiator just below the radiator cap and then it diverts to both radiators.  The cooler water is then fed back to the pump and pushed around the engine before then exiting up towards the right-side radiator again.  If there is a blockage in the system, there would be back-pressure which causes the water to be forced out the overflow tube.  This would be more noticeable at high revs because the pump is pushing more water.

Somewhere in your system, there is a blockage, most likely caused by air.  My preferred method of burping the cooling system (getting the air out of it), is the following:

• Start with a cold engine
  
• Remove radiator cap and start engine
  
• Bring up to operating temperature
  
• Watch the water flowing from the pipe into the top of the radiator (it will be just a trickle because the thermostat is closed)
  
• At about 76 degrees celcius the thermostat will open
  
• More water should now begin to flow into the radiator, and it is at this point that air will likely be seen.
  
• Let the system run like this until it reaches about 90 degrees celcius
  
• Optionally, let it get to 110 degrees celcius and confirm the fan comes on, and that the temperature drops or stabilises
  
• Stop the motor, replace the radiator cap and then go for a ride to see if it's fixed

Don't worry if some coolant spills onto the floor as it gets hot in there and the water level rises - you can always fill it up again!

Good info Mate.  Sometimes when you think you know what your doing something like this comes along along and shows you just how little you do know.  I have had the same problem with my 98 VFR800 since I changed the coolant a couple of years ago.  Although most of my riding is done in the winter months I have gotten caught in heavy traffic a couple of times and lost part of coolant from boil overs.  Changed the fan control switch in an effort to resolve the issue with no success.  Also looked at going to lower set point control switch as mentioned in another article.  Yesterday afternoon I followed your "burping" process, got all the air out of the system and things are now back to normal and is working like it should.  GOOD JOB on your posting and great information for future reference.

Chers,

Lester

Well if you warped the heads and got a leak there would be cloudy oil in the sight glass, and perhaps a tell tail smell coming out of the exhaust.  Replaced the radiator cap? I wonder if in fact the thermometer your reading is accurate? If coolant is leaking it stinks to high heaven, you can smell it easy enough. The tech he did a pressure test on the radiator?  

Things you should look into

Obstruction - missing fairing pieces that direct air into rads, insects or debris in the radiator fins, fan stuck?

Water pump, slow or intermitant coolant flow? A bad impellor?

Replaced the thermostatic switch on the rad, is the connector making positive contact?



I had this problem with my XR650, it was always overheating blowing out all the fluid into the bottle.  So I bought a radiator cap off a KLR which is rated higher pressure, fixed my problem!

If a compression test shows one or more cylinders with low compression, also perform a leak down check.  This will pinpoint where the leakage is occuring.  If you have a bad head gasket you should see bubbles in the coolant system.  Leak down checks are very good at finding the cause of low compression, in addition to the bubbles in the coolant, hissing through the injectors indicates a bad intake valve, hissing through the exhaust a bad exhaust valve and hissing from the engine oil fill hole indicates bad rings.  Leak down gauges are readily available and can be inexpensive for a single gauge unit to pretty pricey for a dual gauge, internally calibrated unit.  Hope this helps.

that's a lot of grief!!

i think you need to pressure test cooling system  in order to rule out possible bad head gasket.

Or look for a kinked or pinched water hose somewhere...