cooling

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waddy1200

Active Member
Posts
141
Location
near scunny
Right ive read rave and was wondering if i was right in my thinking on this one. The cooling system on my 2001 4.0 has a bypass system on it where as when it is cold and before it gets up to temperature it bypasses the thermostat and goes round the engine, heater matrix etc etc. Now my temp gauge sits bang on in the middle no loss of coolant but the top of the radiator is hot top pipe is hot, heater blows out hot air bottom pipe is hot but the bottom of the radiator is stone cold and so is the pipe that leads to the thermostat. Now would i be right in thinking that if the thermostat wasnt working during this cold weather it wouldnt overheat and temp gauge wouldnt move from the middle due to the heater being on full all the time while im using the car there for taking a lot of the heat away from the engine.
 
no its only cold on the radiator side of the thermostat i would have thought it would open up as ive got a 12 mile daily drive to work and 12 back all of it done at around 50 mph
 
cheers james im keeping an eye on it but the temp gauge has never moved think i might just put a new thermostat on it to be on the safe side id rather eyre on the side of caution than run th gauntlet. i must be getting old cos not long ago id have said of bugger it ill worry about it when i breaks.
 
temp guages often dont straight away and sometimes not till a bit late but to stop asap, theres a latent effect , doesnt it allways , my 3 amigoes on my td5 came on and after checking found wheel sensor so i thought id put a new hub kit on at the end of the week after all thos wheel bearings run for ages like that next day wheel was dangerously wobbly ,£200 just when i didnt want it
 
Mine is the same at the moment and I have two stats thast I have tried as long as the top hose is hot and the top of the stat is hot you should be ok if in doubt take the stat and put it in a pot of boiling water and watch t open
 
no its only cold on the radiator side of the thermostat i would have thought it would open up as ive got a 12 mile daily drive to work and 12 back all of it done at around 50 mph

The thermostat on a petrol P38 will be opening in under a mile - let alone 12. It must be opening or you'd be overheating in a big way in 12 miles. The P38's cooling system's capacity is marginal to say the least.
 
cheers james im keeping an eye on it but the temp gauge has never moved think i might just put a new thermostat on it to be on the safe side id rather eyre on the side of caution than run th gauntlet. i must be getting old cos not long ago id have said of bugger it ill worry about it when i breaks.

You haven't got a temperature gauge - you have a pointy traffic-light system. The gauge acts as a gauge in the warming-up phase, then the needle will sit dead centre as long as your temperature is within the normal range, should you exceed that range it'll go to three quarters, and then the red zone with the light on if you exceed that second range.

Most modern cars work that way these days. It stemmed from research done by Ford in the 80s, customers preferred gauges to warning lights (they found them comforting) but didn't like fluctuation of the temperature gauge as it introduced doubt about the dependability of the car. So the gauge became a warning light system in the gauge format. The days of prior warnings of doom via a slightly higher than normal temperature reading are long gone. Your "temperature" gauge will lie to you until you run into trouble.
 
You haven't got a temperature gauge - you have a pointy traffic-light system. The gauge acts as a gauge in the warming-up phase, then the needle will sit dead centre as long as your temperature is within the normal range, should you exceed that range it'll go to three quarters, and then the red zone with the light on if you exceed that second range.

Most modern cars work that way these days. It stemmed from research done by Ford in the 80s, customers preferred gauges to warning lights (they found them comforting) but didn't like fluctuation of the temperature gauge as it introduced doubt about the dependability of the car. So the gauge became a warning light system in the gauge format. The days of prior warnings of doom via a slightly higher than normal temperature reading are long gone. Your "temperature" gauge will lie to you until you run into trouble.
+1, the temp gauge on the L322 gets to the middle around 75degC - operating temp is 105degC and the gauge will move from centre above 115degC....

So the temp range with the needle sitting square centre is between 75degC and 115degC....
 
The thermostat on a petrol P38 will be opening in under a mile - let alone 12. It must be opening or you'd be overheating in a big way in 12 miles. The P38's cooling system's capacity is marginal to say the least.

So any ideas why the top of the stat and top hoses are hot and the bottom of stat and hose from rad to stat are cold - mine is doing the same with new rad new stat and new cap - just interested
 
Ha not down here positively balmy
And gents another question if the system has lost so much coolant that the temp sensor is not sitting in fluid what does it read ? When mine blew top hose off and cooked the temp guage never budged have since checked and it does register overheating odd to me
 
Ha not down here positively balmy
And gents another question if the system has lost so much coolant that the temp sensor is not sitting in fluid what does it read ? When mine blew top hose off and cooked the temp guage never budged have since checked and it does register overheating odd to me

If there is no coolant around it, it can't register the coolant temp. Try running the engine without coolant and watch where the temp gauge is when the engine seizes up. :D:D
 
Well I was lucky and got away with it but the needle stayed bang in the middle which I thought was worrying so if the cooling system drops the lot you dont know until way too late
 
On the L322 when the Water Pump went south and leaked....Dash temp gauge read Hot....Digital Read out read -128...photo attached....
 

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So any ideas why the top of the stat and top hoses are hot and the bottom of stat and hose from rad to stat are cold - mine is doing the same with new rad new stat and new cap - just interested

It doesn't matter if it's -15 out there - there's not enough coolant capacity in the system with the thermostat closed to keep a V8 happy. The diesel by nature puts slightly less demand on the cooling system - even so it take quite a lot of energy to haul 2.5 tonnes of steel along through a permanent four wheel drive system. The thermostat must be working or stuck slightly open if the car's not rapidly overheating.
 
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