Hitachi zx 25 overheating...

W

Will zaxis 25

New member
Hello all, any wizards out there? I'm trying stop my zx25 overheating. The manual for it doesn't mention the cooling system.
IMG_20210703_191249.jpg
I've put a new thermostat in, the rads are clear, I've flushed the system. Nothing has stopped it from overheating after about 10mins of work. I'm wondering if there is air in the system. I've attached a photo with an arrow pointing to a possible bleed point. Does anybody know what this is? It has ptfe tape in the threads. The big pipe next to it seems to go to the radiator but doesn't seem to get water in it. Any help much appreciated.
Will
 
JD450A

JD450A

Feral as Fk
Hello all, any wizards out there? I'm trying stop my zx25 overheating. The manual for it doesn't mention the cooling system. View attachment 25787I've put a new thermostat in, the rads are clear, I've flushed the system. Nothing has stopped it from overheating after about 10mins of work. I'm wondering if there is air in the system. I've attached a photo with an arrow pointing to a possible bleed point. Does anybody know what this is? It has ptfe tape in the threads. The big pipe next to it seems to go to the radiator but doesn't seem to get water in it. Any help much appreciated.
Will
Buy a coolant/combustion gas test kit. Personally I would be jumping towards Head gasket. in terms of the engine.

Is the Hydraulic oil up to spec and full and when was the last time the Hydraulic filter changed?
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
Hello all, any wizards out there? I'm trying stop my zx25 overheating. The manual for it doesn't mention the cooling system. View attachment 25787I've put a new thermostat in, the rads are clear, I've flushed the system. Nothing has stopped it from overheating after about 10mins of work. I'm wondering if there is air in the system. I've attached a photo with an arrow pointing to a possible bleed point. Does anybody know what this is? It has ptfe tape in the threads. The big pipe next to it seems to go to the radiator but doesn't seem to get water in it. Any help much appreciated.
Will
I'd say that plug is for a pressure bleed to get all the air out of the system ... big air trap in that top hose to the left.
head lacking water and will quickly turn to steam, super heating the coolant system

some renaults had a similar issue and had a pressure head bleed tool ... basically a header pipe on a rad cap to force all the air out of the system ... could never get it out the various bleeds with out using at least 3ft of head
someone's DIY jobbie
1625339803723.png
 
craig

craig

Well-known member
I'd say that plug is for a pressure bleed to get all the air out of the system ... big air trap in that top hose to the left.
head lacking water and will quickly turn to steam, super heating the coolant system

some renaults had a similar issue and had a pressure head bleed tool ... basically a header pipe on a rad cap to force all the air out of the system ... could never get it out the various bleeds with out using at least 3ft of head
someone's DIY jobbie
View attachment 25788
Looks like its on the inlet manifold to me.
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
Looks like its on the inlet manifold to me.
That plug is on inlet manifold pipe is air intake pipe, check fan belt tension,
I did wonder TBH as t'other hose looked to be top hose, but never having seen one, I'd placed my faith in the OP as knowing it was a water jacket ... would explain the crazy convoluted rubber routing though and almost asked the Q myself. :rolleyes::unsure:
 
W

Will zaxis 25

New member
Buy a coolant/combustion gas test kit. Personally I would be jumping towards Head gasket. in terms of the engine.

Is the Hydraulic oil up to spec and full and when was the last time the Hydraulic filter changed?
I will find out about the hydrolics. As for the head gasket, there is no oil in water or v.v. And it doesn't seem to get pressurised before it gets hot.... I will look into the test kit thanks👍
 
JD450A

JD450A

Feral as Fk
I will find out about the hydrolics. As for the head gasket, there is no oil in water or v.v. And it doesn't seem to get pressurised before it gets hot.... I will look into the test kit thanks👍

Won't always get cross contamination. Exhaust gas test is cheap and piece of mind. Other question would be whether the impeller on the water pump is heating up and then spinning on the shaft.

Trouble is there's all manner of potential issues on the little machines that will make them hot..

R.E the big pipe is the Air intake pipe for the engine.
 
W

Will zaxis 25

New member
I did wonder TBH as t'other hose looked to be top hose, but never having seen one, I'd placed my faith in the OP as knowing it was a water jacket ... would explain the crazy convoluted rubber routing though and almost asked the Q myself. :rolleyes:

That plug is on inlet manifold pipe is air intake pipe, check fan belt tension,
Yes belt is good, fan is drawing well👍
When you say overheating are you certain it really is overheating and not a faulty temperature gauge ?
When it gets to the red line and starts beeping it's bubbling to the expansion tank. So I think the sensor works...
 
W

Will zaxis 25

New member
Won't always get cross contamination. Exhaust gas test is cheap and piece of mind. Other question would be whether the impeller on the water pump is heating up and then spinning on the shaft.

Trouble is there's all manner of potential issues on the little machines that will make them hot..

R.E the big pipe is the Air intake pipe for the engine.
Thanks, we had a mechanic out to try and sort it, they fitted the thermostat. I guess he would have checked that it was pumping then, but I wasn't around so I'll double check that.
So is it water in the exhaust gasses you're testing for?
 
W

Will zaxis 25

New member
I did wonder TBH as t'other hose looked to be top hose, but never having seen one, I'd placed my faith in the OP as knowing it was a water jacket ... would explain the crazy convoluted rubber routing though and almost asked the Q myself. :rolleyes::unsure:
Yeah sorry I think I confused things saying I thought the pipe went to the rad😁
 
JD450A

JD450A

Feral as Fk
Thanks, we had a mechanic out to try and sort it, they fitted the thermostat. I guess he would have checked that it was pumping then, but I wasn't around so I'll double check that.
So is it water in the exhaust gasses you're testing for?

That sounds like a fitter more than a mechanic.


Testing for combustion gases in the water jacket.....

You won't be able to check the water pump without removing it, which will require a new gasket..... if he's not charged for a gasket it's not been off.
 
W

Will zaxis 25

New member
Is the machine hard to start/labouring when running? If so the hammer petel could be stuck on slightly.
If that's OK I'd be checking the water pump
It doesn't seem to be labouring but saying that, I guess I might just be used to how it sounds.... I'll look into that thanks
 
A

Alan caddy

Active member
It's usually exhaust gases in the coolant, that your checking for, you can get cream that changes colour if combustion gasses are in the water cheap at car parts shops, when cold you can take of a hose heading to heater hold up high start machine and water should pump out if not water pump not working at all
 
JD450A

JD450A

Feral as Fk
Yeah sorry I think I confused things saying I thought the pipe went to the rad😁

Edit, I see your only at Bovey Tracey..... Buy the Combustion test kit. PM me your phone number and I will pop up and look next Friday night if you want..... No charge to look see but a donation to my beer fund is appreciated if the problem is solved.
 
W

Will zaxis 25

New member
That sounds like a fitter more than a mechanic.


Testing for combustion gases in the water jacket.....

You won't be able to check the water pump without removing it, which will require a new gasket..... if he's not charged for a gasket it's not been off.
OK thanks very much👍
 
W

Will zaxis 25

New member
It's usually exhaust gases in the coolant, that your checking for, you can get cream that changes colour if combustion gasses are in the water cheap at car parts shops, when cold you can take of a hose heading to heater hold up high start machine and water should pump out if not water pump not working at all.
Thanks Alan 👍
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
It's usually exhaust gases in the coolant, that your checking for, you can get cream that changes colour if combustion gasses are in the water cheap at car parts shops, when cold you can take of a hose heading to heater hold up high start machine and water should pump out if not water pump not working at all
trouble is it could work fine when cold ... have seen an impeller let go on the shaft when hot before .... Rory had one on a truck a few years ago ... difficult to test safely when hot, in situ
 
Top