TD5 Wont Run up to Temperature After New Rad

Hi Guys

I have been battling with this for a few months. I changed out the original (leaking) radiator for an aluminium replacement (not Alisport). Since then I have been unable to get her up to temperature, unless I am giving her beans going up hill on a motorway. I have changed the thermostat three times with no result.

My understanding was the thermostat remained closed until the engine was up to sufficient temperature to require cooling from the radiator. So if the radiator is more efficient the thermostat should just remain closed for longer.

Any ideas ?

Thanks

that's a new one on me.
I have to drive mine to get it warm, and as long as my heaters are not on full it stays there. Is your temperature sender working OK? I'd be tempted to use a temperature gun or something on a hose when it's running and see if it is reading correctly. Does your heater work ok? if so it probably is up to temp

Have you routed the hoses correctly from & to the thermostat? When the motor has been running a while, have you felt the hoses for temperature differences? Mind your fingers on fan & belt. That should give an indication if the thermostat is jammed open. As you've changed the 'stat it shouldn't be that. Bled out, it shouldn't make any difference how big the rad is, the 'stat should regulate the temperature.

It worked fine until you changed the rad ... I'd go over exactly what you did when you changed it, hoses in the correct place, none pinched or twisted, electrics in correct place, thermostat right way up, bleed it again, and again ...

Thanks guys, Im fairly confident the sender does work at is shows temp if i give her beans. Heater does not work (unless giving it beans). I will get a digital temp reading of lower and top hose and report back. My old local Indie fitted the rad, been back once and they pointed to the thermostat so i changed it a couple of times.

When you have replaced the stat have they all been from the same manufacturer and supplier, could be a duff batch? Have you tried pouring water through it to make sure it is closed and you could also try testing it in a pan of hot water to make sure it opens at the correct temp.

You have increased the cooling capacity of the rad as alli rads generally have a larger cooling surface (bigger tubes), they are designed for performance engines that are upgraded.
Buy a cheap digital thermostat and measure at temp sender see if same as gauge. If it is look at changing the thermostat for one that runs hotter 78 Deg or so. That's your problem as Land Rover rads are designed to run in deserts ( that's why so large), My message is don't mess if you don't understand thermodynamics and Boyles / Charles Law as you will fook up your engine as many others do.......

The rad makes no difference to the thermostat, that opens based on the temperature of the water coming from the engine, the thermostat shuts off the flow to the rad isolating it from the system.

Fit a higher temp thermostat possibly?

Oh yes it does mate Boyles and Charles Law is at work here pressure / temp/ volume co efficient. Lower pressure and increased volume means lower temp, increase volume / lower temp thus pressure. If the water coming from the rad is at lower temp / pressure then stat will have no effect as it cannot operate as it should as its bypassed. Remember water boils on Everest at 43 Deg. It makes me laugh as people fit bits and mess despite Land Rover spending millions and millions on design not understanding how engines actually work

Stat is bypassed when it's closed though so water doesn't flow through the rad?

Exactly my point its open when it should not be so engine full cooling and not reaching temp

if that's the case, do as I used to on a old racing motorbike, tape up half the radiator to get it up to temperature

Make sure its not a Harley you use then and only Jap crap, gorilla tape is recommended and tell the DVLA of modification along with insurance company!

viscous fan could be locked up solid and with ally rad its just too much if you dont have a viscous fan id look at fitting one or remove you existing fan and go electric . i have an electric fan from an evoqe on my series .

Right, sorry I have been trying to figure this out with a few other things (disco transfer box and new brakes all round) (another post later). Since my last post I have flushed the system and fitted a genuine thermostat, which has made no difference. I am now running a front rad muffler just to get it up to temperature on motorways, but concerned about intercooler/EGT issues.
The general consensus from most of folks I talk to is that you can have as large a radiator as you like, the thermostat determines how much coolant is sent that way to cool down and in turn cool the engine.
Not sure I understand where hobroydharry is coming from though.

- Viscous fan is not locked up, only operating at low speeds and startup.

So have I put the pipes on the wrong way round when I first changed it (4 thermostats ago) and not noticed?, resulting in continuous flow through the rad (even when closed). Does anyone have a picture of one fitted to a defender TD5?

thats a bloody conumdrum and a half . try starting from cold and see if water is circulating it shouldnt until it gets up to temp as to what might cause this id guess at it bypassing the stat somehow , will it warm up anymore with the heater turned to cold ..????

Water circulates from start, bleed screw on top hose will flow from the beginning. Putting the heater on will bring the temp down slightly.

The gauge appears to be working, as it changes in line with what you would expect.

My only thought is that I have the thing plumbed in wrong.

im fairly certain water shouldnt be flowing from cold my m51 bmw doesnt do it other than through the heater system im guessing something has been fitted wrong and is allowing water to bypass the stat im not familiar with td 5 engine so i cant really say what to try or give you an idea of a cause but id certainly be inclined to think the water is getting past the stat somehow and not allowing it to close off the flow thus getting up to temp . try getting a decent pic of your engine bay on here and possibly someone more familiar with td5 might take one look and point out a incorrect pipe etc

Hi guys.

I have been on and off trying to diagnose this issue and still have not managed, the engine does get up to temp on long motorway journeys, but never to a proper temp unless i close the rad muff. But that raises other concerns.

As mentioned this occurred after fitting an aluminium rad, it has a genuine thermostat fitted. Its the third one tried.

My only thought left is that it is not fitted correctly. I have a pretty ropey picture of it fitted, have i got the two hoses at the top the wrong way round ?
(the angles exit from the top is going towards the passenger wing).

Can anyone shed some light on this, the next step is take it to a specialist and see if they can sort it.

Thanks

Hi all
I am going to resurrect this thread as it still seems to be an issue. I have been battling for some time now to get my TD5 to get up to temp and stay there since a new aluminium rad was fitted, a few points:
- Long runs up hill, gauge will respond with the engine running up to normal temp and the heater will work
- If I'm not working her she will cool right back down again
- 20 min drive to work int he morning will not see the temp gauge move at all.
- I was using a rad muffler for a while but I was concerned about EGT temperatures creeping up.

What I have done so far:
- She is on her third thermostat, a genuine one
- I have bled the system countless times, with the front of the landy facing up a steep bank

Before I go and fit a fourth thermostat or pay an Indie a fortune to dig around for the problem I was wondering if anyone here could spot something I have missed or has experienced a similar issue.
Is there a definitive way to bleed the system?

Ta muchly