Coolant boiling and engine getting v hot

[aaron0288]

Now I've only just purchased this bike, and this problem didn't show itself on the test ride.

It's a 1991 l model with 34,000 on the clock, and has just had the head gasket done. After a small half an hour ride, when I turned the engine off, I could hear the coolant bubbling, and a bit of steam came out of the front of the bike. When for another short ride, the bike seemed to get very hot, and more bubbling noises when turned off again.

Could it be a sticky thermostat?

[Mori Man]

That or a huge airlock in the system.

While cold remove the rad cap and see if the coolant is visable , top up as necessary.

Start bike and let it warm up on choke (this is best done on paddock stand or have some one hold it up for you)

The coolant level should drop but looking in you should see it flowing past. As the bike warms up it will expel air , if you give it gentle rev's you will see the coolant rising

Have you rad cap in hand and as soon as you see it rising on it's own - usually when the thermostat opens and your getting the full capacity flowing , bung the cap on before it all starts pouring out.

NB* Your potentially messing with hot fluids so wear protection ( Durex will not work! )

That should have expelled any air in the system.

If it is still pressurising the system its more likely the head is warped and thats causing the problem - this usually leads to piles of steam coming out of your exhaust as coolant flows into the cylinders and makes it a bitch to start again.

If thermostat has never been replaced it will do no harm putting a new one in - its a bit of a fart about getting the cover off otherwise I would have said pull it out and run with out one, if it takes a month to warm up or never gets to running temp then thats been your problem but having done mine just have a new one ready to go back in. First sign of trouble switch off though or you will cook the new unit which has probably happened when it blew the head gasket originally.

MM!

[cargo]

Could just be an air lock but in all the time I've had zxr400 I've never experienced that happening and I'd have the radiator off and drained a lot...............


I'd have had serious questions for the previous owner....................like why did you spend all this money on a head gasket job and the sell the bike ?
Who actually did this work and is there a receipt ?
Was the head properly torqued down ?
What was the reason for replacing the head gasket ?
Was the engine seriously over heated pre new gasket ?


The steam you can see could be coming from a lose hose connection or a hole in the rad.
Did you check the coolant level before you took the bike for a second outing ?
Did you top it up ? (answering no to that is the wrong answer)
.
You need to throughly check the entire cooling system make sure there is no air in there and ALL connections and hoses are tight and not leaking either when hot or cold.
Visually check the radiator for holes/leaks again hot and cold.
Check that the water pump is working
Check for kinks in all hoses
Check the thermostat operation..................remove it and put it in a container of hot/boiling water and watch it open or not as the case may be.

If the cooling system check out 100% ok then you looking at maybe a blown head gasket question is then why ? was it a botched job bythe previous owner ? or is there something more fundementally wrong like a warped head ?


Frankly I'd be very wary of buying a bike if the seller had told me with a smile " it's got a new head gasket".......................big big alarm bells would be ringing in my head and I wont some good answers to some questions.

[aaron0288]

Checked the coolant level which was fine. There was no sign of oil in the coolant and vice versa.

[aaron0288]

Well today it took a few go's to start.

Then within no more than literally 3 minutes of it starting (from cold), the needle was 3/4's up the temp gauge! It then proceded to point to the big red h within another 5 minutes! Stopped the bike, no bubbling sounds this time, no steam. Started the bike up again, revved it to about 6000rpm, hey presto, steam from the front of the engine, and a little dribble of coolant on the floor. Noticed that the fan doesn't work, but am starting to think that's the least of my worries.

[cargo]

When you say steam from front of the engine..............where exactly.
IF it is coming from the engine as opposed to the raditor then looks like blown headgasket.

note the big IF

as old old and wise man once said measure twice cut once


Make sure of EXACTLY what the symptoms are before setting about a fix

[CaNsA]

The same thing was happening on mine.

HG had indeed gone.
Got it replaced by a trusted bike grease monkey and it was sorted.

If you see bubble under the rad cap then its a defo HG issue dude.
And as said before, countless time i have drained dry and filled the cooling system with out getting an airlock.

[Tirpitz]

And as said before, countless time i have drained dry and filled the cooling system with out getting an airlock.

+1 on that. I've just drained and flushed my cooling system as part of getting a laid-up bike back on the road. Refilled with coolant as easy as shelling peas, no airlocks, absolutely simple job, runs perfect.

I'm afraid it looks way more serious than that. At this time of year I'd be surprised if a holed rad would manifest overheating quite as quick as you experienced the last time. Sounds more like gasket issues.

[aaron0288]

I'm new to these bikes so forgive me for the question, but the coolant tank on the right hand side of the bike, just above the oil level glass, is that the overflow tank? If so, where's the normal coolant tank?

[cargo]

I'd not call it an overflow tank.................expansion tank would be more accurate and yes thats it on the right just above the oil sight glass.

there is alos a cap on the radiator for filling/toping up...................but only when it's cold or you'll get burnt fingers

[aaron0288]

So coolant needs to be topped up from the radiator cap? Expansion bottle is obviously full.

[Mori Man]

So coolant needs to be topped up from the radiator cap? Expansion bottle is obviously full.

Yip top up coolant from rad cap.

There is a Max/Min line on the expansion tank - you want it somewhere from the middle to three quarter mark.

Haven't blown a head gasket on the bike before but one did go on a car I had - temp went sky rocket and I left a fog cloud behind me NO coolant in oil though but had to get a section welded between the two inner combustion chambers on the head then it was skimmed. Car sounded sweet as a nut when I bolted it all back together (gave it a de-coke too)

[aaron0288]

Update.

The bike gets hot only when on the move, and that's over 40mph. Keep it a low revs (under 5k), and below that speed, even sitting in traffic, and it stays at normal operating temp.

[cargo]

problem solved then keep it under 40

[Mori Man]

No chance of a ticket