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Discussion Starter · #1 ·
My DD is a '93 200tdi 110.

I have zero issues with it starting, driving, or overheating on a regular basis. Temp Guage warns up to dead center and stays there. I always keep the coolant level right.


However, the once or twice a year I take long drives 2-4 hours on the highway, the temp Guage goes all the way up to the beginning of the red line, and I have to stop and try to let it cool off.

I'd like to fix whatever the problem is so I don't have to worry.

What would be the recommended replacements and/or fixes to solve the issue?
 

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It could be one of several things, but I’d start with the cooling system and Make sure your radiator is clean (when was last time you had it flushed and cleaned/inspected?) and your viscous fan clutch. Also, stock gauges may make a mountain of a mole hill. Verify temp. It may just be a little warm and not overheating. I have my radiator cleaned every few years.
 

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Discussion Starter · #3 ·
It could be one of several things, but I’d start with the cooling system and Make sure your radiator is clean (when was last time you had it flushed and cleaned/inspected?) and your viscous fan clutch. Also, stock gauges may make a mountain of a mole hill. Verify temp. It may just be a little warm and not overheating. I have my radiator cleaned every few years.
Was thinking that re the radiator, I have never had it cleaned in my ownership of about 5 years. Is it worth cleaning vs just getting a brand new one for ~$300?

I wouldn't be as concerned with the gauge if it always ran like that. It concerns me more that it's only when I am really working the engine, which to me seems like it can't stay cool at that workload.
 

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Get an infrared temp gun and take a true reading when in the middle and near the red so you know exactly what the temp really is before you begin any fixes.
 

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Go Mundo Maya!
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a new HD EX MOD version radiator and intercooler pack is cheap and easy to install. Check your injection pump fuel pin and make sure it’s not grooved or sticking, new thermostat and flush coolant. Easy driveway repairs and will surely make a different on your daily driver.
 

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Discussion Starter · #6 ·
Get an infrared temp gun and take a true reading when in the middle and near the red so you know exactly what the temp really is before you begin any fixes.
I did that last year w an infrared temp gun and it was def getting HOT, don't remember the exact reading, Trouble is I am making a long trip in a month and wont be able to get it up to that temp before then to get a readont.

a new HD EX MOD version radiator and intercooler pack is cheap and easy to install. Check your injection pump fuel pin and make sure it’s not grooved or sticking, new thermostat and flush coolant. Easy driveway repairs and will surely make a different on your daily driver.
Link? Thank you!
 

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1991 Defender 110 Beach Runner 2 Door 200tdi
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a new HD EX MOD version radiator and intercooler pack is cheap and easy to install. Check your injection pump fuel pin and make sure it’s not grooved or sticking, new thermostat and flush coolant. Easy driveway repairs and will surely make a different on your daily driver.
I am running a Chinese aluminum radiator from Amazon and it takes a drive through hell to get it above 180. Also have a Rev TEC fan that come on at 195, but rarely comes into play.

Primecooling 3 Row All Aluminum Radiator for Land Rover Defender & Discovery I, 300TDI 90/110 2.5 4X4 BTP2275 https://a.co/d/ew8WG1R

 

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That is the correct location for the needle. The middle is low and means the thermostat is leaking. The gauge center is designed for the earlier engines with the 82 C thermostats. This means they show high with the 88 C thermostats.

Double check with an IR temperature gun. If it still bothers you install a better gauge. The highest you should see is around 94 C at which point the fan should engage. If it goes above that, you fan viscous unit is the first thing to check.
 
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Discussion Starter · #9 ·
That is the correct location for the needle. The middle is low and means the thermostat is leaking. The gauge center is designed for the earlier engines with the 82 C thermostats. This means they show high with the 88 C thermostats.

Double check with an IR temperature gun. If it still bothers you install a better gauge. The highest you should see is around 94 C at which point the fan should engage. If it goes above that, you fan viscous unit is the first thing to check.
Typically on a 5-30 minute drive my gauge sits right around dead center. I can check with the gun but again, rarely get it to that "red" zone but twice a year and don't want to get stuck. Where should I aim the temp gun?

I haven't done any radiator work in my 5 years of ownership...

Thanks!
 

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Typically on a 5-30 minute drive my gauge sits right around dead center. I can check with the gun but again, rarely get it to that "red" zone but twice a year and don't want to get stuck. Where should I aim the temp gun?

I haven't done any radiator work in my 5 years of ownership...

Thanks!
Measure the temperature on the thermostat housing between the head and the thermostat. It is very common for thermostats to leak and you run cold most of the time. With a good sealed thermostat, the engine should go up to the opening point (88C, 190 F) fairly quickly and then sit there. It will only rise above this temperature when you work the engine fairly hard without enough natural air flow over the radiator. At that point the fan is needed. With these trucks it is rare that the fan is needed when driving on the road. Because of that, you may not know the fan is not working until you hit the right circumstances to require it. If you are finding temperatures over 200 F (94 C) and the fan is not locked up, then that is your issue. Failure of the viscous unit is very common.
 

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1991 Defender 110 (ROW) 200tdi
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Ditto on the IR temp gun. I was having similar issues on mine, where it would spike way up. Coolant levels were good. Checked with IR gun, and the temp was fine. Ended up being that the nut that holds the ground wire on the back of the gauge had vibrated off, so just another case of bad grounding!
 

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My DD is a '93 200tdi 110.

I have zero issues with it starting, driving, or overheating on a regular basis. Temp Guage warns up to dead center and stays there. I always keep the coolant level right. View attachment 475888

However, the once or twice a year I take long drives 2-4 hours on the highway, the temp Guage goes all the way up to the beginning of the red line, and I have to stop and try to let it cool off.

I'd like to fix whatever the problem is so I don't have to worry.

What would be the recommended replacements and/or fixes to solve the issue?
I have a 1993 Defender 200 Tdi and I was experiencing the same issue. I chose to replace most of the cooling system (thermostat, flushed radiator, viscous fan, temp sensor) etc and then I finally realized that the truck wasn’t actually overheating but rather the temp gauge was malfunctioning as resistance changed in the circuit because as we know the wiring of Defenders of this age is usually a mess.

i agree with taking an infrared temp gun and measure the temps of the head in the back middle and front.
After you exceed 30 mph the viscous fan has little benefit. So I’d check it and it’s an easy replacement but at road speed it has little to do with the cooling effect.
 
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