Coolant leakage - how worried should I be?

[Mikkel]

I've had on several occasions that my Kawasaki zx7rr has been spilling a bit of coolant, typically after riding a low speeds through town and such.

Today coming back from a ride I heard bubbly noises from the cooling system as I put her in the garage and she spilt a bit of coolant as well.

I changed all of the coolant about 6 months ago and gave the entire system a good flush. When I bought the bike in march the temperature controlled switch for the fan was replaced and I have since replaced the temperature sensor for the temperature gauge. Alas, it appears that the gauge itself isn't working too well.

So what could be causing this? And exactly how concerned should I be? What would be the best way to sort it out?

[skidMark]

I've had on several occasions that my Kawasaki zx7rr has been spilling a bit of coolant, typically after riding a low speeds through town and such.

Today coming back from a ride I heard bubbly noises from the cooling system as I put her in the garage and she spilt a bit of coolant as well.

I changed all of the coolant about 6 months ago and gave the entire system a good flush. When I bought the bike in march the temperature controlled switch for the fan was replaced and I have since replaced the temperature sensor for the temperature gauge. Alas, it appears that the gauge itself isn't working too well.

So what could be causing this? And exactly how concerned should I be? What would be the best way to sort it out?


Quick possible fix is you havnt topped it up right....

fire bike up....remove radiator cap.... let it idle for 10-20 seconds and refit the cap with the bike still running.

if that doesnt fix it you may have a stuffed thermostat or something. :cool:

[The Stranger]

Could be one of the following.

Over temperature - Is the fan coming on?

Under pressure (allowing the water to boil too soon)-damaged/incorrect radiator cap

Over pressure due to head gasket leak or cracked head etc - Uh oh, take it to a mechanic, there are a couple of possible tests I am aware of for this one.

[Mikkel]

I opened up the overflow reservoir after I had stopped and steam was coming out of it and the coolant was bubbling away. The leakage isn't at the reservoir, I haven't pinpointed it - it's a bit difficult to do without removing the fairings.

[Bute]

this happened to me a few weeks ago , and in my situation i drained the coolant to slightly above minimum level and it cured the problem , my guess was there was too much coolant in the expansion chamber , may not work for you but did for me :)

[Mikkel]

Just had a play around with the old girl...

Coolant level was worringly low. My guess is that there's a leak somewhere in the system that has slowly drained the system of coolant, to the point where steam is able to form in the system. The formation of steam has caused increased pressure and forced even more coolant out of the system. Anyway, I've topped it up and will remove the fairings sometime soon and have a good thorough look at it. I fear however that the leak is in the radiator itself as I could see a bit of steam rising off the radiator as the bike was idling away. Might be worthwhile tearing out the radiator itself and have it tested - replaced if necessary. At least the bike is running well and I guess nothing bad has happened to it. Quite impressive since it would have been running mostly on steam for a while...

Anyone who can recommend a digital temperature sensor to replace the original one?

[MSTRS]

Sounds to me like you have a small leak somewhere. That will stop the system pressurising as it should and therefore boiling at or below the temperature that the fan should kick in at. All exacerbated by high air temps at the moment.

It could be a leak in the radiator, a hose, or an o-ring in the engine (hope not). Also could be a blocked thermostat (not fully opening), or a dud radiator cap, or a faulty temp sensor for the fan, or incorrect antifreeze %.
Or something else...

First thing to do is take your bike to someone who can pressure test it. Then work from there.

[vifferman]

What WobblyBelly said.
Also (plus!) once you get steamage happening, it is possible to get a vapour lock in a hose, so that coolant doesn't circulate properly (And your gauge won't register correctly coz it's not in fluid). This kinda exacerbates (like masturbates, but worrisomely more troublesome) the "spitting out coolant" thing as well, as the engine gets hotter.
It could be just a bubble in the system, as Skiddy alluded to. If so, what he said is correct. Dunno 'bout Kwackasakis (never owend one), but on the VFR the procedure involves squeezing/tapping a couple of the hoses while blipping the throttle with the rad cap off.

[Mikkel]

Thanks guys. I'll go see a man about a dog and a radiator today and hopefully I'll come up with a plan. I think I'll tear out the radiator first thing and have it tested. There is most definitely a leak somewhere in the system and I have a gut-feeling it's the less-than-brand-spanking-new radiator.

Also, consulting the workshop manual made me a bit wiser. There is, among many other useful things, a specific procedure for bleeding the cooling system.

[MSTRS]

Thanks guys. I'll go see a man about a dog and a radiator today and hopefully I'll come up with a plan. I think I'll tear out the radiator first thing and have it tested. There is most definitely a leak somewhere in the system and I have a gut-feeling it's the less-than-brand-spanking-new radiator.

Also, consulting the workshop manual made me a bit wiser. There is, among many other useful things, a specific procedure for bleeding the cooling system.

Don't yank it out just yet. If the radiator has an 'ole, there should be stains apparent. The leak (if you have one) might be elsewhere so you wasted time etc removing the rad. Test the whole system in situ.
Can I suggest you drain the system, run a flush through it to remove any crud, then refill with correct coolant mix, bleed according to your newfound useful thing. Then see what happens re problems.

[vifferman]

Yeah, what WobblyBelly said.
It could be anything (or nothing) in the cooling system that's leaking. F'rinstance, on many bikes, when the impeller on the waterpump is fookt, coolant dribbles out of a weep hole on the bottom. It could also be a leaky gasket under the thermostat or waterpump.
Or the rubber flangeygaskety thing on the radiator cap.
Or a hole in the radiator core, or crack in the upper/lower parts.
DON'T PANIC!
See what the manual says.
Fairing off, take of the radiator cap and see what the level is, top it up, top up the overflow bottle, then start the bike and look for leakage.
Observe the coolant in the radiator for bubbles. Look for leaks in the hoses, especially under or near the clamps. Squeeze them to see if there are any soft spots or bulges. Look for steam, dribbles, etc.
Take your time, and do lots of looking at ALL the parts of the colling system.

[Mikkel]

Don't yank it out just yet. If the radiator has an 'ole, there should be stains apparent. The leak (if you have one) might be elsewhere so you wasted time etc removing the rad. Test the whole system in situ.

Good idea. It's a bit hard to see any stains or anything like it on the radiator though.


Can I suggest you drain the system, run a flush through it to remove any crud, then refill with correct coolant mix, bleed according to your newfound useful thing. Then see what happens re problems.

That's pretty much what I did when I changed the coolant back 6 months or so ago. Although I didn't use the sneaky bleeding technique as it were.


Yeah, what WobblyBelly said.
It could be anything (or nothing) in the cooling system that's leaking. F'rinstance, on many bikes, when the impeller on the waterpump is fookt, coolant dribbles out of a weep hole on the bottom. It could also be a leaky gasket under the thermostat or waterpump.
Or the rubber flangeygaskety thing on the radiator cap.
Or a hole in the radiator core, or crack in the upper/lower parts.
DON'T PANIC!
See what the manual says.
Fairing off, take of the radiator cap and see what the level is, top it up, top up the overflow bottle, then start the bike and look for leakage.
Observe the coolant in the radiator for bubbles. Look for leaks in the hoses, especially under or near the clamps. Squeeze them to see if there are any soft spots or bulges. Look for steam, dribbles, etc.
Take your time, and do lots of looking at ALL the parts of the colling system.

I never panic - I just get mildly irrational ;) But I always have a towel handy, so it can not go completely haywire.

Fairings off is step one I think and then the rest of what you are suggesting will follow.
Afterwards I'd better drain the system and refill with a proper coolant mix since I just topped it up with tap water yesterday. At that point the level was very low indeed - put just under 2 liters into the system.
I'll go looking for a pressure tester too - pretty sure it's redundant though, since there's bound to be a leak somewhere.

Anyone with an idea about how much I'd be looking at for a new radiator if it's kaput?

[vifferman]

Afterwards I'd better drain the system and refill with a proper coolant mix since I just topped it up with tap water yesterday.
If you don't just buy premixed coolant, you can buy the concentrate and get 10 litres of distilled water from the supermarket for under $10.

Don't panic about the radiator just yet - if it's leaking, it's probably still repairable.

[Mikkel]

Well, I took the fairings off. And fired her up. There is at the very least a leak at the waterpump - from somewhere up behind the pump.

I'll wait for the bike to cool down a bit before I drain the coolant and take off the waterpump for inspection. If the leak is what I think it is the unit will need replacing... And at least now I know for sure that the fan works fine.

As for the radiator. I'll tear it out when I have the system drained anyway and then have it tested here in Chch. They can restore it too if it's not working properly.

Chch water is apparently fairly soft. But I'll get some distilled water to go with the concentrate. I think it'll be at least a few days before I'll be putting it all back together again. Oh joy, and in the meantime the motard is waiting for a new clutch cable... at least I haven't managed to sell the 250 yet, so that's kinda fortunate now.

[Mikkel]

Yep, the waterpump is due for replacement... some time ago.

[Richi]

Yep, the waterpump is due for replacement... some time ago.

There goes 300 bux :wavey:

[Mikkel]

There goes 300 bux :wavey:

Yep - $313.99 to be exact. Better than having to get a new radiator though... they're more than a grand.

I just hope it won't take too long to get it.

[imdying]

You could take the old one to Smiths Regrinds to see what the say about rebuilding it.

[Mikkel]

You could take the old one to Smiths Regrinds to see what the say about rebuilding it.

According to the workshop manual it needs replacing if:

1. There's coolant leaking from a small hole on the back side of the pump.
or
2. There's corrosion and/or damage on the impeller blades.

1. is where the leak was at. And the impeller blades and housing are both quite corroded.

[Max Preload]

The 'small hole' is usually just the drain so coolant doesn't make it's way into the oil via a leaking seal (there's one seal either side of the cavity on the shaft that the hole drains). They can still often be dismantled and successfully repaired.

Have you had a timeframe for the new part? (I love a laugh!)

[Richi]

According to the workshop manual it needs replacing if:

1. There's coolant leaking from a small hole on the back side of the pump.
or
2. There's corrosion and/or damage on the impeller blades.

1. is where the leak was at. And the impeller blades and housing are both quite corroded.

The water pump sounds fine. You better get that radiator looked at :shifty:

[Mikkel]

I got my new waterpump today - nice, shiny, sleek and pretty - and I've had the radiator checked (and it works without leaking).

So I'm almost set for putting it all back together.

Now, the temperature gauge on the dash doesn't read out correctly. Replacement gadget is fairly expensive... and so I was considering getting hold of a digital temperature gauge that I could fit into the dash where the old unit sits right now.

So, has anyone got some brands and models of digital temperature gauges that they could recommend?

[Max Preload]

What makes you think the gauge doesn't read out correctly when you haven't even reassembled, filled & 'burped' the cooling system? The senders don't work in steam or hot air and are usually located where the air pockets form.

Given you had a leak, then you'd have had such a pocket. I would suggest you put it all back together, fill the cooling system, run the bike until the thermostat has been open a few minutes (check the lower hose temperature to verify), switch it off and allow to cool, check and top up the coolant as required and restart.

Besides, if anything, it's most likely for the sender to be faulty, not the gauge itself.

[Mikkel]

What makes you think the gauge doesn't read out correctly when you haven't even reassembled, filled & 'burped' the cooling system? The senders don't work in steam or hot air and are usually located where the air pockets form.

Given you had a leak, then you'd have had such a pocket. I would suggest you put it all back together, fill the cooling system, run the bike until the thermostat has been open a few minutes (check the lower hose temperature to verify), switch it off and allow to cool, check and top up the coolant as required and restart.

Besides, if anything, it's most likely for the sender to be faulty, not the gauge itself.

I've replaced the sensor already.

There was no significant travel on the gauge even when the system was filled with coolant and the bike allowed to heat up to the point where the fan kicked in (~95 degrees celcius). The only movement from the guage was a movement equivalent to approximately the width of the cool-marker.

The gauge is not dead - but I believe it's not working properly. There is a fairly long-winded procedure to check if the calibration is ok, but I haven't bothered with it. The sensor is new, the electrical connections are ok - through exclusion the gauge should be the problem.
Unless, of course, as you say there has been an air bubble sitting right at the sensor. I find that unlikely - but I'll consider the geometry of the system and decide whether it is at all plausible.

[Max Preload]

Is the sender under the thermostat housing or on top of it?

[Mikkel]

On the underside. I'll do some tests tonight. Had a chat to a mate who's an auto electrician and he said that earthing problems at the thermostat housing could result in a reduced readout at the gauge.

[Max Preload]

On the underside. I'll do some tests tonight. Had a chat to a mate who's an auto electrician and he said that earthing problems at the thermostat housing could result in a reduced readout at the gauge.

They normallly bolt the housing to the frame via a bracket, but it's possible.

[Mikkel]

Ah, the pitfalls of 2nd hand bikes.

Tonight I did a couple of experiments and I observed the following.

If the temperature sensor is removed from the thermostat housing, given a good earth connection (wire to lower triple clamp in this case) and then dunked into hot water (80-100 degrees celcius) the needle moves to approximately a third of the full scale.

So after having concluded that earthing was the issue I had another look at the workshop manual and concluded that somebody had put the earth-wire onto the wrong bolt - the one which holds the thermostat housing onto the frame (incidentally it's isolated with a rubber bushing to reduce vibrations). :rolleyes:
See the 1st picture - the red ring indicates where the earth-wire was connected and the green ring where it's supposed to be.
Another somebody (ego) failed to make that connection... :sleep:

Anyway, I decided to check up on the thermostat as well. So I took it out and chucked it in a pot filled with water. I hooked up the cooking thermometer and heated up the water. The thermostat started opening around 64-66 degrees (manual say 58-62, but that's close enough for me since I dunno how precise the cooking thermometer is).

However, I do think that somebody (maybe the one from before) failed to use distilled water with the coolant. See picture 2.
Should I scrape out those deposits or just leave them as they are?

[Max Preload]

So the red circled bolt is an electrically poor connection to the thermostat housing by virtue of it being a vibration damping mount of rubber. That makes sense. That bolt looks substantially bigger though - how did it fit?

No need to use distilled water (you want demineralised anyway if you're being that fussy). The build up looks very minor anyway and is most likely because of the bad earthing of the housing causing electrolysis not mineral deposits.

[Mikkel]

So the red circled bolt is an electrically poor connection to the thermostat housing by virtue of it being a vibration damping mount of rubber. That makes sense. That bolt looks substantially bigger though - how did it fit?

The diameter and thread of all four bolts are the same. I suppose somebody may have thrown one of the original ones away and replaced it with something else during a (perhaps the) botched maintenance job where the earth-wire was misplaced.


No need to use distilled water (you want demineralised anyway if you're being that fussy). The build up looks very minor anyway and is most likely because of the bad earthing of the housing causing electrolysis not mineral deposits.

Depends upon your location I'd expect. I understand we have quite soft water here in Chch, dunno where you'd have hard water in NZ - but if you did calcium deposits like those will occur when water is heated close to the boiling point. I've seen much worse in electrical kettles in Denmark (very hard water) than what's inside that housing...
I should be able to get deionised water at the lab if I wanted.