Wierd Overheating Issue

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
Naughty-Monkey

Naughty-Monkey

Member
Posts
30
Location
Guernsey
Hi all,
Just replaced the radiator on my 300tdi. Put in a new thermostat at the same time. However, it overheats with the thermostat in. Take it out, all ok.
I have triple checked for air locks and pressure tested the system which is good.
So i thought it was a falty thermostat. Bought another and its the same.
Tested both in a saucepan of water and they work, at boiling. Proper boiling point, not a degree before.
Obviously the thermostat is not opening, but why not? I think its in right. All clean.
Engine all runs fine with no thermostat in. But obviously i dont want to run it like this.
Anyone got any ideas? Im baffled.
Thanks
James
 
hmm, on the gauge. But it would get all the way almost to the red.
Admittedly its not boiling and steaming or anything, but the gauge is about 9\10 and the radiator still cold.
 
Seems hot, but i must admit not screaming hot. surely the thermostat would open before the gauge gets to the red ? Unless the temp sender is broken or something?
 
Can I ask has it always read hot ? Also is it original to the car (the engine)?

J
 
Hmm, that could be it. The car is mostly a 300tdi but it was rebuilt by the bloke i bought it off. The engine is 300tdi but could have come out of a disco? The axle is disco as I think you identified last week.
 
Marjon. No, before radiator and thermostat change it was fine and only got over half (on the gauge) when i was towing heavy loads. I chucked the old thermostat out. Wish i hadnt now.
 
Naughty-Monkey said:
Marjon. No, before radiator and thermostat change it was fine and only got over half (on the gauge) when i was towing heavy loads. I chucked the old thermostat out. Wish i hadnt now.
Click to expand...

So if you undo the bleed point on the thermostat housing it is full of coolant?
Did you place the thermostat with the vent hole at the top?

Cheers
 
Naughty-Monkey said:
Marjon. No, before radiator and thermostat change it was fine and only got over half (on the gauge) when i was towing heavy loads. I chucked the old thermostat out. Wish i hadnt now.
Click to expand...
one temp sender is blue/green the other black
does top hose get hot and rhs of rad as looking from the front ie intercooler side
 
Sounds to me like it’s something you changed then.

you tested 2 stats and both seem to not open early enough.
Or the water is not getting round the rad properly, is going straight down and out.

does the whole rad get warm when you run it without the stat?

J
 
what i'd do, start engine from cold with expansion cap off
let it get hot, if it starts boiling/spewing coolant, then its overheating and needs fixing. if it doesn't then either the sender or dash is wrong.
 
The hose at the top on the rhs is cold with thermostat in. Without, its hot and the entire rad is hot. I even filled the radiator completely from the rad plug.
I did put it with the vent hole at the top, it wont go in any other way.

Is the thermostat the same for disco\defender?

Its so odd. Everything is good, without the thermostat. Rad is warm throughout, heater works, all pipes seem warm but not too hot. As soon as i put the thermostat in, temp goes up to 9\10 before I have to stop.

Agreed, it must be something ive changed.
I changed:

Radiator
Thermostat
Cyclone vent on rocker cover.
To try and fix the overheating, i also changed afterwards, that valve thing that comes from header tank and splits into 2. Made no difference.
 
Think as it was fine.
Then you had the overheat.

do you have an IR thermometer thingy? To check the flow in the rad when it’s warming up.

I would go with the stat some say they have had bad ones before. Think it’s 88° but don’t know the engine. Or how hard they Maybe to bleed.

I once had a dodge and it could be a pig, go up hill and glue a big dollop of air the gauge would drop to cold;)

J
 
I just read somewhere else that the standard 300tdi thermostat is supposed to open at 88 degrees. Im sure when I tested both the termostats they didnt start to open until the water in my saucepan was proper boiling. Might get a temperature sensor in and see.

Could it be anything to do with the antifreeze i put in? Surely not.
 
Naughty-Monkey said:
I just read somewhere else that the standard 300tdi thermostat is supposed to open at 88 degrees. Im sure when I tested both the termostats they didnt start to open until the water in my saucepan was proper boiling. Might get a temperature sensor in and see.

Could it be anything to do with the antifreeze i put in? Surely not.
Click to expand...
stats open slowly, you you put the pan on a high heat then it will boil before you notice the stat opening
 
Naughty-Monkey said:
I just read somewhere else that the standard 300tdi thermostat is supposed to open at 88 degrees. Im sure when I tested both the termostats they didnt start to open until the water in my saucepan was proper boiling. Might get a temperature sensor in and see.

Could it be anything to do with the antifreeze i put in? Surely not.
Click to expand...

yes check stats in a pan with a proper temp reading do it slowly.
No antifreeze won’t change that.

Naughty-Monkey said:
I can borrow a IR thingy from work. What do I do, run the engine and check where its heating up?
Click to expand...

You can get a better idea of actual engine temp.
Plus you can follow the heat in the rad. Your rad (I believe) goes top “in” across to other side (probably using half the rad)down then across back to the bottom and “out”
Check it doesn’t go straight down (just incase)

if the gauge is getting hot but the engine really isn’t then go back to the sender.
I am sure you can work out the rest without me typing it :)

Also just to chuck something else in the mix. As you said it was fine then started overheating.

Waterpump??


J
 
Naughty-Monkey said:
The hose at the top on the rhs is cold with thermostat in. Without, its hot and the entire rad is hot. I even filled the radiator completely from the rad plug.
I did put it with the vent hole at the top, it wont go in any other way.

Is the thermostat the same for disco\defender?

Its so odd. Everything is good, without the thermostat. Rad is warm throughout, heater works, all pipes seem warm but not too hot. As soon as i put the thermostat in, temp goes up to 9\10 before I have to stop.

Agreed, it must be something ive changed.
I changed:

Radiator
Thermostat
Cyclone vent on rocker cover.
To try and fix the overheating, i also changed afterwards, that valve thing that comes from header tank and splits into 2. Made no difference.
Click to expand...
are you going for a run to get it hot during tests or just stood with engine running
 
You must log in or register to reply here.

Similar threads

M
Series 3 200tdi overheating
Replies
5
Views
328
tottot
tottot
Birdbrain
200tdi Defender thermostat
Replies
1
Views
293
miktdish
miktdish
tarphenry
P38A thermostatic control for fans
Replies
15
Views
770
Datatek
Datatek
Lucknow Landy
Running hot after a new thermostat
2
Replies
24
Views
1K
Jack Handle
J
Lucknow Landy
Still running hot after new thermostat
Replies
7
Views
672
Dippypud
Dippypud
Back
Top