Overheated ZX - any ideas?

[ChristoT]

This is something that has been puzzling me all month.

As you're probably aware, my ZX-4 blew up on the 31st of December (yeah, fuck you too, 2013!), and I'm trying to work out why. And how! How could a bike travelling at 70mph through cold air overheat? It's a watercooled engine, true, but why would it blow up at that speed? It would be more understandable if it had been in town, but not, this was on the A303, braking for the Andover slip road (seeing a friend). And the speed at which it blew up concerned me too - one minute it was registering just above stone cold, and then within under 10 seconds, the needle was registering the red zone. The knocking noise followed soon after, and now the entire coolant system smells of burning rubber.

I won't be able to get the engine off to strip it for a while, so does anyone know what would cause the bike to overheat so dramatically to give me places to look? The oil/water pump idea seems to have been a red herring - when the mechanic at Hatfield drained the oil, there was nearly no contaminatio, aprt from what would be expected from a bike that had been standing a while. Looks like the head gasket is OK too.

The rad fan, on the other hand, has half melted!! 

[alexanderfitu]

Did the water pump not fail? Did the system have enough coolant in it as well?

[ChristoT]

Did the water pump not fail? Did the system have enough coolant in it as well?

The pump may have failed, but the bike was full of coolant - it hadn't lost anything to the outside or the oil! I'm getting confused.

But even if the coolant pump HAD failed - with a 70mph cold wind blasting the front of the engine, I'm amazed it overheated as fast as it did, if at all! Especially as it was cruising along in top gear!

[alexanderfitu]

If the pump fails the engine will heat up very quickly, even going along at 70mph, but then gauge would probably still show cold as I think the sensor is in the top of the rad.

[Hamos]

possibly a blockage?  Some crud in the coolant system broke off and blocked an engine passage.  No cool water in, but heat still coming out?

Or on oil passage blockage leading to seizure?

[ChristoT]

If the pump fails the engine will heat up very quickly, even going along at 70mph, but then gauge would probably still show cold as I think the sensor is in the top of the rad.

On the ZX, the gauge is at the bottom left of the rad. But I don't know it that's the inlet or the outlet.

possibly a blockage?  Some crud in the coolant system broke off and blocked an engine passage.  No cool water in, but heat still coming out?

Or on oil passage blockage leading to seizure?

I suspect a blockage, The header had some mysterious, thick red goo at the bottom of it that came out neon pink after being mixed with distilled water  . I suspect the rad and pipes are similarly clogged.

Seizure, I doubt, as the bike still starts cold, and has run fine up to 3/4s temperature (hotter than it ever used to, admittedly), with no funny noises.

[rustyrider]

A common problem on some cars is that the impeller in the water pump is plastic pressed onto a steel shaft and comes loose.  Any restriction in the cooling system is going to increase the resistance on the impeller making it start to slip.  Once it starts slipping it will heat the plastic very quickly and soon the shaft is spinning but the pump is doing nothing.  If that is the case, you only need to flush the cooling system and fit a new pump.

If it's the same as something else of course......

[robby boy]

Thermostat might be stuck shut, not opening and letting the hot water circulate, or a blockage somewhere.

[midden]

if the fans is melted perhaps it failed altogether. could be atleast partly to blame

[ChristoT]

if the fans is melted perhaps it failed altogether. could be atleast partly to blame

Yeah, it's melted the shaft, and it was banging against the radiator (not the knocking noise I heard on the road though). But at 70mph, the fan shouldn't BE on! What alarms me is how fast the system failed. That's why I fear a major fuckup.

Thermostat might be stuck shut, not opening and letting the hot water circulate, or a blockage somewhere.

One of the first avenues I plan to investigate.

A common problem on some cars is that the impeller in the water pump is plastic pressed onto a steel shaft and comes loose.  Any restriction in the cooling system is going to increase the resistance on the impeller making it start to slip.  Once it starts slipping it will heat the plastic very quickly and soon the shaft is spinning but the pump is doing nothing.  If that is the case, you only need to flush the cooling system and fit a new pump.

If it's the same as something else of course......

There's a really nasty burning smell from the rad cap, like scorched rubber. Not pleasent, and very worrying! I plan to give the pump a full overhaul.

On a ZX-4, the pump runs both the oil and coolant system. If that failed, I guess the engine could have overheated from oil starvation, and no cooling.

Certainly an avenue to investigate!

[Deefer666]

Ideal moment to stuff a zzr-600 engine in it then!

[darrsi]

If you had a blockage or clogged up waterways then the coolant would've overheated, got pushed into the expansion tank then it would boil like a kettle and get dumped on the floor if it couldn't circulate properly.
Then when the bike cools down any remaining fluid would get sucked back into the main system, leaving you with a very low or empty expansion tank.

I've actually watched it do this on my previous bike.


That's why it's always worth the occasional quick shake of the bike on the centre stand to check the coolant level is where it should be, 'cos it's a very good indicator if the system's in good shape or not.
If all is well the levels should pretty much stay the same when the bike is cold, other than a very minor top up every few months if at all needed.

[ChristoT]

If you had a blockage or clogged up waterways then the coolant would've overheated, got pushed into the expansion tank then it would boil like a kettle and get dumped on the floor if it couldn't circulate properly.
Then when the bike cools down any remaining fluid would get sucked back into the main system, leaving you with a very low or empty expansion tank.

I've actually watched it do this on my previous bike.


That's why it's always worth the occasional quick shake of the bike on the centre stand to check the coolant level is where it should be, 'cos it's a very good indicator if the system's in good shape or not.
If all is well the levels should pretty much stay the same when the bike is cold, other than a very minor top up every few months if at all needed.

Oddly, the header level didn't budge an inch, and the full coolant level was present and accounted for.

If the water pump went poof though, the oil pump would have gone too. Oil starvation, and lack of cooling...  This is beginning to sound pricey...

[CRH]

why dont you just flush the entire system take out you thermostat incase that was the problem to begin with?...then try running it again just on water and see what happens ....test the thermostat seperatly in a saucepan of hot water up to boiling point and see if it opens and try to record the temp at opening use a temp probe ....my jag years ago did same thing when it overheated due to thermostat jamming shut?...and i got that burning smell like you describe!!

[ChristoT]

why dont you just flush the entire system take out you thermostat incase that was the problem to begin with?...then try running it again just on water and see what happens ....test the thermostat seperatly in a saucepan of hot water up to boiling point and see if it opens and try to record the temp at opening use a temp probe ....my jag years ago did same thing when it overheated due to thermostat jamming shut?...and i got that burning smell like you describe!!

The cooling system is the first thing I'm checking, CRH.

My worry is the horrific knocking noise from the engine. And as the coolant pump and oil pump are linked on this bike, oil starvation is a real concern, along with the damage that can do.

[darrsi]

Well it seems you're not alone with the melting fan anyway!

http://www.kawiforums.com/ninja-250r/165083-250r-radiator-fan.html


Some ideas here as well:


http://answers.yahoo.com/question/index?qid=20081116071756AA3ijbo

[darrsi]

Did you put the coolant in yourself, or was it there from the previous owner?
If there was more water than coolant then the fluid would boil like kettle water, as coolant/antifreeze raises the boiling point, as well as lowering the freezing point.

[ChristoT]

Did you put the coolant in yourself, or was it there from the previous owner?
If there was more water than coolant then the fluid would boil like kettle water, as coolant/antifreeze raises the boiling point, as well as lowering the freezing point.

Previous owner.

All I did was clean some of the gunk out of the header and top it up with distilled water.

[Gnasher]

All I did was clean some of the gunk out of the header and top it up with distilled water.

What gunk?

[ChristoT]

All I did was clean some of the gunk out of the header and top it up with distilled water.

What gunk?

I suspect a blockage, The header had some mysterious, thick red goo at the bottom of it that came out neon pink after being mixed with distilled water  . I suspect the rad and pipes are similarly clogged.

Seizure, I doubt, as the bike still starts cold, and has run fine up to 3/4s temperature (hotter than it ever used to, admittedly), with no funny noises.

When I was in France, I checked some of the fittings etc (and found an alarming number of them loose). I also found this thick, gel-like gunk in the header. I cleaned quite a bit out, and topped up the header with distilled water before setting out. I would have done a full coolant flush and replace, but I had other bike problems that seemed more urgent. I was planning on doing a full flush when  I got back to Chatteris, but the bike never made it.

[darrsi]

Did you put the coolant in yourself, or was it there from the previous owner?
If there was more water than coolant then the fluid would boil like kettle water, as coolant/antifreeze raises the boiling point, as well as lowering the freezing point.

Previous owner.

All I did was clean some of the gunk out of the header and top it up with distilled water.

So there is always the chance that the previous owner has been topping up with just water as well.
I think you really need to get rid of the old fluid, and probably best to do a Radflush as well, then refill with the proper mix just so you know for sure what's in there.


And as Gnasher says, what gunk are you on about?

[ChristoT]

Did you put the coolant in yourself, or was it there from the previous owner?
If there was more water than coolant then the fluid would boil like kettle water, as coolant/antifreeze raises the boiling point, as well as lowering the freezing point.

Previous owner.

All I did was clean some of the gunk out of the header and top it up with distilled water.

So there is always the chance that the previous owner has been topping up with just water as well.
I think you really need to get rid of the old fluid, and probably best to do a Radflush as well, then refill with the proper mix just so you know for sure what's in there.


And as Gnasher says, what gunk are you on about?

First I need to strip the engine to check for damage. So it will be getting  full clean anyway.

I have no idea as to what the gunk actually was (it smelt pretty foul!) I suspect it was old coolant which had mostly evaporated, leaving the stuff in the coolant as a concentrate in the system. It didn't flow that well, and obstinately sank.

[Gnasher]

It sounds to me you've been unfortunately sold a dog not that you want to hear that or that it's needs pointing out to you but I think that's the whole point.   It's very, very likely based on what you've said most of the rad matrix is blocked by the said gunk, it's also possible the said gunk is a form of rad weld put in to seal whatever the real reason is/was for the owner selling the bike!     I've seen things of a very similar nature before, it's also possible the head or liner/s are holed somewhere rad weld can when mixed with escaping combustion gases turn to goo as you put it!  It's very likely I'm wrong as trying to diagnose complicated issues via owners descriptions is very difficult if not impossible without seeing things for your sake I hope I'm wrong!   I'd seriously look at Deefer666 idea though 

[ChristoT]

 A ZXR400 engine should fit, I might do that if the ZX engine is completely dead.

[darrsi]

Coolant on a hot engine is normally a sweet smell.


Radweld could cause gunk, blockages and a different smell, so that's a very good shout.