Woodstock Walt
Silver Member
Hi, all. I recently completed this repair/modification on my 2019 4540 with 230 hrs. I thought I'd share some info on the cause/effects of this common problem, as well as the fix.
If you're like me and live in a cooler climate and own a Mahindra 4540 or 4550 that has not had this part installed, you've likely noticed the coolant temperature gauge rarely moves off of the lowest peg. The only time I'd ever seen mine climb off the lowest peg was while grading our gravel road with a 6' box blade on an 80* summer day.
This was concerning to me because I am familiar with the negative effects of operating a cold diesel engine under load. I use my 4540 with a Winco 15k PTO generator to power our house during the frequent power outages we experience year round, so obviously operating the engine at ~2000 RPM for hours on end with cold coolant is a long-term reliability concern.
I tried covering the radiator with cardboard, which allowed the coolant temp the rise just slightly above the coolest peg after running the generator for multiple hours. I removed the mechanical fan and replaced it with a Flex-A-Lite e-fan with an independent thermostat, under the assumption that the fixed mechanical fan must simply move too much air over the engine. The e-fan allowed the coolant to rise to operating temp flawlessly, but struggled to keep the engine cool under heavy loads. I'd much rather have an engine that runs cold than one that overheats, so I removed the e-fan setup and reinstalled the factory mechanical fan.
After doing some research, which admittedly I should have done more to start with, I discovered that this is a common problem among 4540/50 owners, often mistaken for a faulty coolant temperature gauge. The cause is the EGR vent hose indicated below, which by design allows coolant to bypass the thermostat. However, this design allows enough coolant to flow that it prevents the engine from reaching operating temperature in colder climates.
If your tractor is affected by this like mine was, you can test the solution by temporarily clamping this line closed with vise grips or a similar tool. I clamped mine shut to test the fix, and sure enough my coolant temp started to rise with the engine idling at 1000 rpm and 30* outdoor air temp. However, a small amount of coolant does need to be able to flow through this line, so this is not a permanent fix.
The fix is to replace the factory vent hose fitting, circled below, with one that restricts the free flow of coolant through this line. The restrictive fitting is sold through Mahindra, I purchased one through my local dealer. The part number is #006029544D1 EGR Vent Adaptor.
Simply disconnect the vent hose attached to the fitting on top of the radiator (make sure you do this with the engine cold), remove the factory fitting, replace it with the new adaptor, and reconnect the vent hose. A deep 17mm socket worked best for me, but be careful as the threads in the radiator are plastic, and one could easily overtighten the fitting and strip the threads.
Here's the factory fitting with the vent hose removed:
(Engine wasn't completely cooled, thus the mess)
And the new restrictive adaptor compared to the factory fitting:
It took me less than 5 minutes to install this part and it made a phenomenal difference in the way my 4540 runs. Once the engine reaches operating temperature, which takes about 10 minutes of high idling for me, it runs much smoother and quieter than it did when it ran cold. More powerful and more efficient, too.
If you're like me and live in a cooler climate and own a Mahindra 4540 or 4550 that has not had this part installed, you've likely noticed the coolant temperature gauge rarely moves off of the lowest peg. The only time I'd ever seen mine climb off the lowest peg was while grading our gravel road with a 6' box blade on an 80* summer day.
This was concerning to me because I am familiar with the negative effects of operating a cold diesel engine under load. I use my 4540 with a Winco 15k PTO generator to power our house during the frequent power outages we experience year round, so obviously operating the engine at ~2000 RPM for hours on end with cold coolant is a long-term reliability concern.
I tried covering the radiator with cardboard, which allowed the coolant temp the rise just slightly above the coolest peg after running the generator for multiple hours. I removed the mechanical fan and replaced it with a Flex-A-Lite e-fan with an independent thermostat, under the assumption that the fixed mechanical fan must simply move too much air over the engine. The e-fan allowed the coolant to rise to operating temp flawlessly, but struggled to keep the engine cool under heavy loads. I'd much rather have an engine that runs cold than one that overheats, so I removed the e-fan setup and reinstalled the factory mechanical fan.
After doing some research, which admittedly I should have done more to start with, I discovered that this is a common problem among 4540/50 owners, often mistaken for a faulty coolant temperature gauge. The cause is the EGR vent hose indicated below, which by design allows coolant to bypass the thermostat. However, this design allows enough coolant to flow that it prevents the engine from reaching operating temperature in colder climates.
If your tractor is affected by this like mine was, you can test the solution by temporarily clamping this line closed with vise grips or a similar tool. I clamped mine shut to test the fix, and sure enough my coolant temp started to rise with the engine idling at 1000 rpm and 30* outdoor air temp. However, a small amount of coolant does need to be able to flow through this line, so this is not a permanent fix.
The fix is to replace the factory vent hose fitting, circled below, with one that restricts the free flow of coolant through this line. The restrictive fitting is sold through Mahindra, I purchased one through my local dealer. The part number is #006029544D1 EGR Vent Adaptor.
Simply disconnect the vent hose attached to the fitting on top of the radiator (make sure you do this with the engine cold), remove the factory fitting, replace it with the new adaptor, and reconnect the vent hose. A deep 17mm socket worked best for me, but be careful as the threads in the radiator are plastic, and one could easily overtighten the fitting and strip the threads.
Here's the factory fitting with the vent hose removed:
(Engine wasn't completely cooled, thus the mess)
And the new restrictive adaptor compared to the factory fitting:
It took me less than 5 minutes to install this part and it made a phenomenal difference in the way my 4540 runs. Once the engine reaches operating temperature, which takes about 10 minutes of high idling for me, it runs much smoother and quieter than it did when it ran cold. More powerful and more efficient, too.
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