LT77 with 200tdi, slight overheat highway speeds.

elbee

Well-known member
Hey guys,
I'm just making sure my truck is running normal for this setup.

I'm currently driving from VA to WA.

I just noticed that the truck will run pretty hot if its doing anything over 60/65-ish. I think the turbo is boosting up the heat as after 60/65 I am outrunning my 5th gear.

I have a vicious fan and an electric on the main radiator, but should i add an electric fan on the intercooler (its an upgraded alisport)? I feel like the truck has plenty of power, but i guess the gearing is too low make use of it all. It would be awesome to be able to cruise at 70, but 60-65-ish has been working alright.

I am running KM1s 255/85/r16 on wolf rims.


truck has been running great, the biggest issue was just getting out of West Virginia on 64.
 

DiscoDavis

Well-known member
What does the gauge say and what are the actual temps?

normal seems to be a tick above half on the gauge. Head temps on mine around 195-200 usually.
 

AdamSanta85

Well-known member
What is hot? My 200TDI also gets hotter on the highway. I would try to keep it under 205-210ish. Usually I get up to 198-202ish if I am trying to do 70-75 for a while. My fan turns on at 205ish. It hasn't turned on yet. 189 - Low 190's around town or taking it easy.
 

javelinadave

Administrator
Staff member
I just noticed that the truck will run pretty hot if its doing anything over 60/65-ish. I think the turbo is boosting up the heat as after 60/65 I am outrunning my 5th gear.
That is my experience too and see my signature for an explanation why.
 

Uncle Douglas

Well-known member
Hey guys,
I'm just making sure my truck is running normal for this setup.

I'm currently driving from VA to WA.

I just noticed that the truck will run pretty hot if its doing anything over 60/65-ish. I think the turbo is boosting up the heat as after 60/65 I am outrunning my 5th gear.

I have a vicious fan and an electric on the main radiator, but should i add an electric fan on the intercooler (its an upgraded alisport)? I feel like the truck has plenty of power, but i guess the gearing is too low make use of it all. It would be awesome to be able to cruise at 70, but 60-65-ish has been working alright.
I am running KM1s 255/85/r16 on wolf rims.
truck has been running great, the biggest issue was just getting out of West Virginia on 64.
Just a guess but do you have a 1.6 transfer case ? When you say you are over running 5th gear that typically only happens if the truck is geared too low. What is happening is that you are revving so high that the water pump is pushing the coolant through the radiator so fast its not having a chance to transfer the heat off. The intercooler isn't your problem- the flow through your radiator is.

Change your transfer case to a 1.4 or 1.2, or slow down to drop the rpm to a reasonable range. Today was a cool day in the region-hope you don't hit 90 degree weather out west.

The function of a turbo is to pump cool air into the intake. The turbo isn't a source of over heating. Incorrect timing, poor cooling, or too much fuel are the ways to overheat a diesel.
 

mgreenspan

Founding Member
I could be automotively illiterate but from all my reading about cooling systems and issues I believe at highway speeds a fan is not doing much of anything to help. A higher speed temp rise would be the result of an inefficient radiator, coolant flow problem, or possibly an air flow problem.

Check the gap between your radiator and intercooler if you have one in front od the other and make sure it isn't huge causing an airflow bubble. Do you have a full width radiator and intercooler, an upgrade might be in order. Another possibility is you may have some wonky water pump pulley that is to big or too small causing to slow or to fast of coolant flow. Our you may need to adjust it. There are Million things. What t case ratio do you have?
 

rocky

Well-known member
I've seen electric pusher fans supplenting the viscous. Good for off road but it's simply vehicle movement cooling things down on the highway.
 

jymmiejamz

Founding Member
Callsign: KN4JHI
You don't need a fan on the highway. Assuming your radiator is in good shape and you don't have a thermostat issue (I had a thermostat on a 300 Tdi not fully open), you need to increase your cooling capacity with a bigger radiator.
 

elbee

Well-known member
thanks for the feedback!
i have a standard setup radiator with intercooler taking up about the quarter of the area.The electric fan is from the previous owner.

Weird thing is that after some days on some rough roads and putting in new coolant (concentrated, not 50/50) I am able to do 70/75 down the highway, even at altitude of 5,000ft+. Not exactly sure why the truck is running better, i feel like may something got un-clogged in the radiator, plus the concentrate is better at cooling? I may try to find a place to flush it, if possible. The fluid still looks clean though.

I'm stopping by harbor freight to pick up an IR thermometer to record temps, as my temp gauge is still the stock one from the 19j (it seems to be accurate, just the needle sits higher on the gauge.).

My transmission is stock 1989 civilian LT77. Where can i find the serial number on it?

Screen Shot 2017-06-12 at 2.09.52 PM.jpg

Screen Shot 2017-06-12 at 2.12.11 PM.jpg
 

globallandrovers

Well-known member
If your car originally had a 19J engine then the main problem is the fact that you will have a 1:6 transfer box fitted like Doug said.

Defenders are not race cars, they are work horses. they were never designed to do 70mph plus speeds.
 

AdamSanta85

Well-known member
Weird thing is that after some days on some rough roads and putting in new coolant (concentrated, not 50/50) I am able to do 70/75 down the highway, even at altitude of 5,000ft+. Not exactly sure why the truck is running better, i feel like may something got un-clogged in the radiator, plus the concentrate is better at cooling? I may try to find a place to flush it, if possible. The fluid still looks clean though.
My understanding is pure concentrate will make your truck run hotter then 50/50 since water transfers heat better.

This truck just came off the ship? If so you injectors might be cleaning up after sitting for a while.

My transmission is stock 1989 civilian LT77. Where can i find the serial number on it?
Crawl underneath and look for a serial number. Shouldn't be hard to find. Same for your transfer case. It will likely have a sticker on it that says if its a 1.4 or 1.2
 

elbee

Well-known member
Yup, this thread is just make my truck is running correctly for the gear ratio and for the fact that the defender is an aluminium tool shed on wheels.

I'm just trying to make sure my truck is running within average specs.
 

mgreenspan

Founding Member
If you aren't complaining about getting to 60-65 your truck is running mostly correct. If you're revving super high and want to go faster for highway or at least the same speeds with lower rpms then swap to a taller tcase ratio. As suggested, you probably have a 1.6. A 1.4 was standard and a 1.2 will drop the rpms more.
 
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