and the plastic one , and the alloy one too .... sorry to be going back to basics ,,, no harm in undoing the return hose from the heater to see whats going on there too ,,, its all in front of you any ways
- Thread starter julianf
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You would think so, but when the viscous fan went on my Merc the bottom hose was red hot.
julianf
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Ive not had time to look at this again until today. Just taken it for a short drive to get the needle off the end of the red...
Laser thermometer is reading about 75c externally. Id imagine that means up to temp internally, but ive changed the sender anyway, and the new one is identical reading to the old. Ill change the gauge later, but...
The bottom pipe isnt really warm. Certainly not hot. Which must mean its a flow issue.
The cab heater is getting hot, so that must mean, surely, its not a water pump issue, but a thermostat OR pipe blockage issue.
Its a new stat, replacing an old one, and there was no change when replacing. Ive got another engine here, so i guess ill pull an old stat from one of them, and either just change it again, or cut it up. But i think it would be wise to take off all the hoses too and make sure there's not a lump of something in any of them. I cant really see how there could be, but the symptoms point to that kind of thing, so there might be.
If i take the top off the headder tank and rev the engine, i can see the odd, infrequent bubble. Obviously this could be head gasket, or it could just be small amounts of residual air from all my messing about.
As i understand it, head gasket failure causes overheating in two possible ways -
a) all the coolant burns off in the cylinder (this clearly isnt the case) and
b) exhaust gasses causing air locks in the coolant system
...which, again, doesnt seem to be the case, as the flow through the heater matrix is good (i know this by all the times i had to stop on the way back the other day - engine off, cab heater blower on, until the heater matrix cooled - then starting the engine again, to start the water pump again, got the air flow from the heater matrix hot again within seconds - so the hot water was certainly being pushed by something!)
Symptoms certainly seem to be pointing to a thermostat / pipe issue, but i am mindful of the infrequent bubbles in the header.
Ill go and pull a thermostat from a breaker engine in a bit.
Laser thermometer is reading about 75c externally. Id imagine that means up to temp internally, but ive changed the sender anyway, and the new one is identical reading to the old. Ill change the gauge later, but...
The bottom pipe isnt really warm. Certainly not hot. Which must mean its a flow issue.
The cab heater is getting hot, so that must mean, surely, its not a water pump issue, but a thermostat OR pipe blockage issue.
Its a new stat, replacing an old one, and there was no change when replacing. Ive got another engine here, so i guess ill pull an old stat from one of them, and either just change it again, or cut it up. But i think it would be wise to take off all the hoses too and make sure there's not a lump of something in any of them. I cant really see how there could be, but the symptoms point to that kind of thing, so there might be.
If i take the top off the headder tank and rev the engine, i can see the odd, infrequent bubble. Obviously this could be head gasket, or it could just be small amounts of residual air from all my messing about.
As i understand it, head gasket failure causes overheating in two possible ways -
a) all the coolant burns off in the cylinder (this clearly isnt the case) and
b) exhaust gasses causing air locks in the coolant system
...which, again, doesnt seem to be the case, as the flow through the heater matrix is good (i know this by all the times i had to stop on the way back the other day - engine off, cab heater blower on, until the heater matrix cooled - then starting the engine again, to start the water pump again, got the air flow from the heater matrix hot again within seconds - so the hot water was certainly being pushed by something!)
Symptoms certainly seem to be pointing to a thermostat / pipe issue, but i am mindful of the infrequent bubbles in the header.
Ill go and pull a thermostat from a breaker engine in a bit.
If your IR thermometer is reading 75 at the point the temp sender goes into the housing then the gauge shouldn't be reading as if it is overheating. (I have a VDO gauge on my 200tdi that reads in degrees and a matched sender - when I use the IR thermometer on mine pointed at the housing around the sender, it reads exactly the same as the gauge +/- a degree or two)
I think the gauge is faulty from what you have written above Julian. Could there be an earth fault? Does it go through the motions of going through normal? How quickly does it go to indicating red hot/overheating? Is it possible someone has muddled the gauge up with the wrong sender?
Bottom pipe being tepid sounds normal too if the rad is doing its job...
To me, this is all pointing to a faulty reading on the gauge.
I think the gauge is faulty from what you have written above Julian. Could there be an earth fault? Does it go through the motions of going through normal? How quickly does it go to indicating red hot/overheating? Is it possible someone has muddled the gauge up with the wrong sender?
Bottom pipe being tepid sounds normal too if the rad is doing its job...
To me, this is all pointing to a faulty reading on the gauge.
julianf
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Could be stuffed, but then everything was getting pretty (subjectively, i had no measuring kit) toasty when i went for the MOT test.
There will be no mis-match, as it was working back in 2015. It could have broken since, but there will not be a mis match.
There could be wiring faults, but, as i understand it, the earth is through the engine block, so if that was bad, not even the IP fuel solenoid would work. There are, of course, degrees of bad. Ill see what happens to the gauge if i connect a jump lead between the head and the battery terminal.
Ive got another of these gauges - i can try that also. It otherwise performs as you would expect though.
A uk company makes an adapter to fit a thermocouple where the (unused on mine) EGR temp sensor would otherwise mount, on the centre of the head. I might get one of them.
julianf
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Just swapped the gauge - no difference.
Its not boiled, as ive been cautious.
The way i understand the gauge - two terminals, one +12v, and one to the sender.
The +12v is from the switched live, via fuse 3. This +ve voltage is then earthed, through the sender, to the housing, and the gauge measures the senders resistance. There's no earth required on the dash for this (other than for the illumination bulb, but that just slots in from the back anyway).
So, my engine earth could be bad, or a partial short on the wire from the gauge (im not certain, but i think the resistance falls as the temperature increases - so a break in the wire would read cold, and a dead short to ground would read hot)
Ive not tried the additional earth to the engine yet. I came in to see (youtube etc) if the thermostat housing could be removed without removing the timing case. Im sure it must be possible, but there is poor access to one of the lower bolts.
(im looking to remove the whole unit from another engine and transplant it)
Its not boiled, as ive been cautious.
The way i understand the gauge - two terminals, one +12v, and one to the sender.
The +12v is from the switched live, via fuse 3. This +ve voltage is then earthed, through the sender, to the housing, and the gauge measures the senders resistance. There's no earth required on the dash for this (other than for the illumination bulb, but that just slots in from the back anyway).
So, my engine earth could be bad, or a partial short on the wire from the gauge (im not certain, but i think the resistance falls as the temperature increases - so a break in the wire would read cold, and a dead short to ground would read hot)
Ive not tried the additional earth to the engine yet. I came in to see (youtube etc) if the thermostat housing could be removed without removing the timing case. Im sure it must be possible, but there is poor access to one of the lower bolts.
(im looking to remove the whole unit from another engine and transplant it)
not done it yet
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Question - dothey drive the gauges from a voltage regulator these days? If it’s giving 12V, instead of approx 10.5V, the gauge will read a lot high than it should. Same might apply to the fuel gauge?
octo0072000
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has this got a ballast resister on the back of the clocks if so change it affects the temp and fuel gauges
julianf
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Wiring diagram shows white wire from ignition switch, to fuse 3 where it then changes to a green wire, which goes to a headder (junction) and then on to fuel and temperature gauges - no resistors etc - i assume they must be integral to the gauges themselves?
Ive not got the fuel level gauge in play at present. Ill test the voltage on the green wire later.
Ive not got the fuel level gauge in play at present. Ill test the voltage on the green wire later.
owas
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Mine did that, said I was overheating when I wasn't.
Put a new wire from the gauge to the sensor and it reads perfect now.
Well It did,My timing belt went the other day
octo0072000
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pushrods in the vice to straighten then new belt and away you goMine did that, said I was overheating when I wasn't.
Put a new wire from the gauge to the sensor and it reads perfect now.
Well It did,My timing belt went the other day
owas
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Unfortunately looks like one of the cam followers have broken too so head off when I can find abit of spare time,
Did find out the land rover specialist I used to do the timing belt about 15k miles ago didn't actually replace anything but the belt, old style pulleys still there
All done properly now.
julianf
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Mine did that, said I was overheating when I wasn't.
Put a new wire from the gauge to the sensor and it reads perfect now.
Well It did,My timing belt went the other day
Ive not even tried to look, im just asking you instead -
Where do you get the connector for the sender from? The push on thing thats round?
(i tested the feed to the gauge - thats a solid 12.whatever volts)
owas
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I think I used a bullet connector, but had to squash it till it would actually fit on tight
julianf
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I think I used a bullet connector, but had to squash it till it would actually fit on tight
...I'll do it tomorrow. Thank you.
julianf
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...or today.
(it made zero difference btw!)
So, today, new sender, new gauge, and new wire. Zero change.
I have ordered a thermowell for the centre of the head (where the EGR sensor fits) and, when that turns up, ill be able to get a digital read-out from an entirely different system.
I might drop the coolant tomorrow, and fill it up with washing powder, and give it a burn. Ive read that can clean up some stuff, and a real-life friend has confirmed it worked for them once, so i guess ill give it a go. Very little to loose.
(it made zero difference btw!)
So, today, new sender, new gauge, and new wire. Zero change.
I have ordered a thermowell for the centre of the head (where the EGR sensor fits) and, when that turns up, ill be able to get a digital read-out from an entirely different system.
I might drop the coolant tomorrow, and fill it up with washing powder, and give it a burn. Ive read that can clean up some stuff, and a real-life friend has confirmed it worked for them once, so i guess ill give it a go. Very little to loose.
julianf
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Probably. I mean i wouldn't even need to take it out of the car - i have all the parts I've already taken out!
I'm not sure its not a display issue either. I do know that all the pipes were hard the other day and weeping at the joints, but that may well just be that id not properly tightened them.
