Thermostat housing leaks

[frankd]

I've been fighting with the cover on the thermostat housing leaking on my '89. When I bought it 2 1/2 years ago, it had a small leak. I took the thermostat housing off and changed all 4 O rings. Everything was fine---for a little while. A month or two later it started leaking intermittantly. Usually when left outisde in the cold, but not always. Last winter I pulled it off again and replaced the O rings again, and also the housing cover because it was mentioned here that they do warp from the exhaust pipe heat. BTW, I put it together with O-rings I purchased at my dealer. It was OK all last year, but this winter it started leaking again. The coldest my garage gets during the winter is about 32 degrees F. When I took it apart, I found that the O-ring was damaged (it looked like it'd been nicked). I remember that it was real hard to get the top on the housing last year and the OE O-ring is 2mm dia., so I installed a 1/16" O-ring. Now it seeps a little bit when it starts to warm up, but when it's hot it's fine.

 

BTW, 1/16"=.0625"

2mm=.079"

 

I will pick up a Yamaha O-ring tomorrow, but I think that something else is wrong because it's happening so frequently. I cleaned up the main housing surface that mates wtih the O-ring so there shouldn't be anything keeping the O-ring from seating. With the 1/16 O-ring, the top felt snug. When I use a 2mm O-ring, it is TIGHT. I'm pretty certain that on my 83' I used a 3/32" (.094") O-ring, but there is no way I could get that to fit this bike. I used a coating of Vaseline to keep from damaging the O-rings when things were assembled.

 

Any ideas?? I'm thinking of heating up the aluminum portion of the housing (in hot water) to get it to expand so that the top will go on easier and not damage the 2mm O ring.

 

 

Frank D.

[cimmer]

I also end up with a puddle under my bike each spring, but never during the riding months. I think the cold is what is causing this and over the 5 winters I have stored the bike it never has been an issue. I just add a little more coolant to the system each spring and go on my merry way.

Hope that helps.

Rick F.

[frankd]

My 83 was that way.....only leaked a little when it was left outside on a chilly night but the 89 is a bit different. It's leaked quite a bit a couple of times, and even had a big puddle under it on a gas stop. Then it'll stop for a month or two. I'll take it back apart again and check everything again. Maybe something will show up. I've even been thinking on finding another thermostat housing and just changing it.

 

FrankD

[GaryZ]

My VR first leaked during a trip last November. It was parked outside the hotel and the temperature dropped to 22 degrees F. It did not leak again, until this last week. I found a thread here on this forum that suggests that the thermostat cap deforms over the years. I have ordered a new one with the o-ring and some seal that was listed.

 

Update: Ordered and received new thermostat cover, o-ring and seal.

Installed and no more coolant leaking on the garage floor.

Edited April 10, 2011 by GaryZ

[flb_78]

Loctite 38657 High Flex Gasket Maker.

 

This is some good stuff. Install your o-rings and then put a thin bead of this around the o-ring.l

 

http://www.jbtoolsales.com/media/ecom/prodlg/LCT-38657.jpg

[OldGazer]

Been goin' thru the "drip, drip, drip" blues myself. The first leak was the Drain/thermostat by-pass O-Ring. Next it was water pump seals (rebuilt the wp this past weekend). Now I'm getting a "cold temperature leak" from around the thermostat area.

 

I think the leak is actually coming from the t-stat hose. When I was looking for the source I wiped every thing dry and then watched for coolant. What I noticed is the end of the t-stat hose is swollen. I suspect the hose has a defect/crack/hole internally and the internal fabric is wicking coolant.

 

In any case, after reading about the t-stat housing, I am going full bore and will change the housing, seals, t-stat hose, and the smaller hose that goes from the radiator to the drain cock.

 

Y'All ride safe...

[mlew]

Since I had more time than money, this worked for me.

http://www.venturerider.org/forum/showthread.php?t=55277

Have not had any problems with it since then.

[frankd]

Mark,

 

Well, I was thinking about coming up with something to brace the gooseneck so it wouldn't warp more, but it's been a b*tch of a week at work and my mind is on overload. Thanks for your brainstorm!!! I will cut one out before I re-install the thermostat housing. I replaced the gooseneck last year, but the new one didn't go together quite flat and this should straighten it out.

 

Thanks again,

 

Frank

[bongobobny]

OK a few things about "O" ring installation! First clean and inspect the "O" ring grooves for nicks and scratches, as even the slightest groove will cause a leak. The rubber wil conform somewhat to irregularities, but not very wel to a surface that has a definate "edge" such as a scratch, especially of the scratch is perpendicular to the ring. The housing and mounting surface should be as flat and smooth as possible. Fine sanding the surfaces with 400 grit paper is actually a good idea as long as you keep the paper flat. The cover can be rubbed against the paper that is on a flat surface, or use a block for the other surface. Clean all grit out of the grooves and inspect after sanding.

 

The "O" rings should be cleaned and inspected under magnification prior to instalation. For lower pressure water applications, a thin coating of vasoline is a good idea, especially to help keep the rings in place when you install them.

 

As far as "O" ring diameter, there is a thing called "fill area" which was already calculated when the housing was designed. Normal fill rate varies but is usually 50% to 60% of the groove area to allow for expansion. "O" rings should fit a little loose as they are "energised" by pressure being applied to one side of the ring changing their cross sectional profile from a circle to an oval, so maintaining their diameter is important. The idea is not to squish as much rubber into the groove as possible, they will leak every time! Also, the material of the ring is important as different materials are designed for different aplications and fluids.

 

This information has been brought to you by your local friendly flight control hardware technician, who has had a lot of experience with o ring failures especially at higher pressures such as 5000 psi but just as important at low pressures less than 25 psi as well! Hope you find the information useful...

[Flyinfool]

OK so how much stuff did you have to take off to get at the t-stat cover.

Mine is now leaking.

It has a small crack in the front. New cover, O-rings and t-stat are on order.

[Keemez]

I'm gonna post in this thread too, even though my leak isn't in the same spot.

 

Mine is dribbling slowly (1 drop every couple minutes) out of the hole where the drain tube jams into the bottom of the stat housing. I see no damage to that oring in there at all (pulled it out, cleaned it up, etc), but it still wants to weep. I tried cleaning and drying the area out and cramming it full of RTV but it still won't seal up good. I guess for $1.46 I could try a new oring. My question becomes: which is the preferred method of installation for this area? I'm not sure whether to set the oring in the housing and then install the tube, or feed the oring onto the tube and then install both into the housing? Install it with or without the highflex slop FLB mentioned above? (I don't currently have any, and I'll be danged if I'm gonna pay 18 bux for a tube of it...) Or... would it be ok to install the old oring AND the new oring on that tube at the same time perhaps? (doublesealed!)

 

MAN this is getting frustrating! At least I seem to have stopped my other leaks.

Edited June 13, 2011 by Keemez

[dingy]

If you do go with the 'Backer Plate' that Mlew linked to, do not skimp on the thickness of the material used to make this plate.

 

Look at the surface just below the 2 red arrows in the 2nd picture and see if this flange is flat from mount hole to other mount hole. Any bowing can be source of leakage.

 

The cover is possible bowing in the center due to heat, fatigue and internal pressure from the compressed o-ring. The metal that is used for the plate needs to exert pressure in the center of the plastic housing marked by the arrow in the 1st picture to do the most good. The left side mounting tab is rather long on the housing so it may be weakened. Also, the two bolts should be replaced with ones 2mm longer to maintain sufficient thread engagement. 1/8" should be thick enough for the plate and also be available at a hardware store.

 

Doubling up on the o-rings would not be something that can be done if o-ring is installed correct.

 

2nd picture shows o-ring groove with 2 arrows, the ring must go in this groove, then plastic housing pushed in metal T-stat casting. If o-ring is put in casting first, it will fail almost immediately.

 

The sealant method is one alternative, not glamorous, but may work. Black permatex is about $5 a tube. It won't take a lot of it to seal.

 

Like Bongo, I have quite a bit of O-ring experience, only on the design end. Was actually designing a part this afternoon with an o-ring groove in a somewhat similar application to this one.

 

The groove width is 1.780" ( 45.21mm) ID x .102" (2.59mm) wide and .048" (1.21mm) deep. My estimate is a 1.5mm thick x 45mm ID dia O-ring.

 

And this is a spare part, in need of cleaning, don't put it back together looking like this. Like your mother said, cleanliness is important.

 

Gary