Failing radiator cap or bad coolant?

LeFrog · Oct 27, 2007

I guess my radiator cap did not do what it was supposed to do, because at one point during my last ride, the coolant got so hot (I was trying Motul Motocool for the first time and I will keep experimenting with it) that it blew out, but instead of going through the overflow hose, it blew through the water pump gasket, a tiny put powerful stream.

I had the OEM gasket with Wurth sealant this time.

Of course I shut off the engine, let it cool down and then added water from the Camelbak, but why did it do that instead of pushing the pressure valve in the rad cap and then overflowing in the bottle?

The rad cap is I believe the original 1.2 PSI. Is it possible for a radiator cap to go faulty?

Also, I hope this is a good coolant, it is advertised as having a 271F (133C) boiling point, vs 256F (124C) for the Engine Ice, and it is also cheaper (around $14 for 2 liters, vs $25 for 2 qts of Engine Ice) and it has some good reviews.

Nevertheless, whatever the product, if the pressure increases to the point that it blows the gasket, I guess the rad cap is failing.

Am I right?

Taffy · Oct 27, 2007

i would say that that is hard to call. but the point is that on your next ride you should have the cap as the fail safe place again.

i would also point out that husabergs have a very low cap pressure whilst at the same time you wnet for engine ice-type-coolant. this would be deemed a weird set-up elsewhere.

regards

Taffy

LeFrog · Oct 27, 2007

Do you think that Motocool is the same type coolant as Engine Ice?

I don't think they are the same type of product, since Engine Ice has no glycol in it. Motocool has a pretty good reputation on the race track.

Taffy · Oct 27, 2007

what i'm saying is that you/we are keeping the bikes from boiling by using these liquids whilst running a light pressure cap. it's the reverse of everyone else. dale has put up before what he runs and can run.

we're talking 1.4, 1.6 no problem. i think he's been to 2.1 or more. and he recommends..........water!

i'm not saying it's right or wrong, A= i don't know and B=i don't care!

just be aware of how it's done elsewhere. if you do a search you'll find dale has posted all this before now.

regards

Taffy

LeFrog · Oct 27, 2007

Well, the issue here is that the pressure cap did not give in as it should have but instead the waterpump gasket did.

I mean really what amount of pressure does it take to blow a 5mm wide paper gasket, with a fair amount of RTV silicone sealant on top and pressed under a properly torque cover?

I would say A LOT MORE than 1.2 PSI.

Well, Dale puts water in there, good for him but I'd like something that boils slightly over 220F and is a bit more heat conductive, as far as I am concerned.

Johnf3 · Oct 28, 2007

Re: RE: Failing radiator cap or bad coolant?

LeFrog said:
Well, the issue here is that the pressure cap did not give in as it should have but instead the waterpump gasket did.

I mean really what amount of pressure does it take to blow a 5mm wide paper gasket, with a fair amount of RTV silicone sealant on top and pressed under a properly torque cover?

I would say A LOT MORE than 1.2 PSI.

Well, Dale puts water in there, good for him but I'd like something that boils slightly over 220F and is a bit more heat conductive, as far as I am concerned.

Actually, pure water is the best when is comes to heat transfer. Better than any antifreeze formulation, whether EG or PG. The antifreeze did not have anything to do with the problem.

Try a new radiator cap. Also, using rtv sealant when not necessary leads to problems as well, at least for me. If it has a gasket already, why goop sealant on it?

LeFrog · Oct 28, 2007

RE: Re: RE: Failing radiator cap or bad coolant?

Because I'd rather be safe than sorry. I don't see why sealant on top of the gasket would be such a bad thing.

Also it says 1,2 on top but I guess this is BAR (17.4 PSI).

The new ones have a 1,4 BAR (20.3 PSI).

I realized my 125 SX has the same exact type of cap, just the 1,4 BAR. Since I do not see it overheating anytime soon, I might be able to save a few and test.

Scouser · Oct 29, 2007

RE: Re: RE: Failing radiator cap or bad coolant?

Le frog,
Some gasket sealant is supposed to replace a gasket and not accompany the gasket. Gasket and sealant is making the gap between the sealing faces wider so therefore weaker to pressure biuld up.
Also remember that pressurising water will cause its boiling point to rise...then when it loses the pressure{leak} it will boil rapidly!
But I agree with you that I would think the cap would relieve the pressure before the gasket failed! You can buy a kit that will pressure test your coolant system...but fits on your machine in place of the pressure cap so that is not much help! Only that it will show if your gasket is failing at less than the 1.2 of the cap!

LeFrog · Oct 29, 2007

Scouser, I agree with what you say, that the gasket + sealant was not the best idea. Wurth sealant alone made a good gasket replacement. It resists to water and coolant, but with a gasket, not good (although it is fine with the left side cover gasket, but under one side only).

But the OEM gaskets look too flimsy to me and I decided to make one out of artificial rubber & fiber gasket material.

Photos below. Sure looks a bit crude, but it fits just fine, allowed me to torque just a bit more than usual, and the extra torquage means a bit more pressure on the gasket.

Yes, I started the bike, yes I let it get hot and no, no leakage. After 2 days, still no leakage either.

Call me the crazy tinkerer.

Taffy · Oct 30, 2007

first of all froggy i admire your ability to have a go at things, that's how we learn the limits and answer the questions that everyone thinks they know the answer too!

a tip for you when making a gasket. first of all you can buy packets of gasket card that is all kinds of thinkness up to 1mm. i've had a set for 25 years and used to make a lot of gaskets.

to make it i suggest a couple of tips for you and anyone else for the future: use a toffy hammer with the gasket laying on the WP housing and using the round end, TAP THE INNER AND OUTTER EDGES to get an outline and half break the gasket paper. next, for the bolt holes: build up a variety of different sized ball bearings and press one by hand down and into the gasket over where the hole is. now tap the Bb with the regular face of the toffy hammer. i used to actually hammer the ID, OD and bolt holes out completely with a toffee hammer and only stop when the paper became gasket and lost it's constituent body.

there are cheap little hollow tubes available that actually create those holes if you look for them. bit you did a good job this time.

and for anyone else listening in: there are two types of radiator cap:

japanese
european

regards

Taffy

Scouser · Oct 30, 2007

Le Frog,
I have to totally disagree with you....that is a well made gasket. The making of a gasket is a lost art. It makes you fell like a real engineer to make a gasket and it does the job, especially when it does that job better than the bought one. I learnt using "Kellog " boxes for inlet gaskets on 2strokes when I had opened the inlet port up, so the "bought gasket" was just too small for my oversize inlets!
Taffy is spot on with the toffee hammer etc. Another option is a very sharp scalpel to cut it out once you make the bolt holes with the ball bearings and clamping the gasket paper with a nut and bolt onto the casing. I have read in a magazine that you can spraypaint the outline of the casing. But I am too impatient to wait for paint to dry!!! So toffee hammer and scalpel is the way forward for me!!
I have not used the Wurth sealents. I get mine free from work...so I only use loctite products! The orange loctite is the stuff i use to replace a gasket. But it has to be torqued down and left 24 hours to set before adding oil or coolant etc to system! This stuff has never let me down on a real variety of engines and applications!

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