How to change the temp probe and thermostat.

[Big-Bird]

The 4M40 has great access to most of the engine bay components. If you ever wondered how to work on some common parts for the cooling system...boo-boo I got you covered!

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Thermostats and Temperature Probes are very important to the 4M40 because when they misbehave they affect fuel economy, glow plug life expectancy(and how the GP system functions). A bad temp probe sends a bogus signal to the computer and prevents the glow plug system from functioning at top efficiency. The Thermostat is stuck open or the rubber seals have gotten hard (age) the coolant will continuously circulate through the rad and in winter the engine won't reach proper operating temps. Fuel won't atomize properly, it certainly won't burn fully and your Delica will have crap fuel economy.

How to fix these???Actually its very easy and best done when the engine is cold.

Remove the intercooler unit and set it aside. Drain and capture the coolant at the butterfly valve located on lower rad tank (drivers side). The valve should be turned 1 to 1.5 turns, any more than that and the plug pops out and coolant sprays everywhere. Also remove the rad cap and the Air-Plug(in my hand) located beside the fresh air intake vent for your heater/AC system

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Next remove the 2 bolts that hold the thermostat housing. There is no need to loosen the rad-hose clamp as the housing and hose can be moved aside easily. There will be a mess soon so get the catch basin positioned for the next part!

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Once the cover is off you will see the nose of the thermostat sticking out. It will need some gentle prying with a screwdriver to get it free....here's the messy part folks.

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Install the new thermostat with the springs in first. The thermostat doesn't care what clock-position its in but I do prefer to have nose laying horizontally. Next bolt up the housing....now if all you needed is a new thermostat then button everything back up including the intercooler.....DON'T install the Air Plug yet!!!!!

Add coolant until nearly everything you drained is poured back in. Next start the engine and watch for fluid to start rising out the air-bleed hose...just before it starts to dribble out install the air-plug and gently tighten.....its only plastic. Add coolant to top off system and you're done. Wash the engine off as coolant can ruin belts and it stinks when it bakes off a hot engine.

[Big-Bird]

The all important tempurature probe sends a signal to the gauge in your instrument cluster and its also monitored by the Glow-Plug system.

The probe is located next to where the upper radiator hose attaches to the intake manifold.

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The probe has 2 contacts and the power connection does have a release clip.
Once the connection has been removed you will need a deep 14mm socket to remove the old plug and to install the new one(the deep socket prevents damage to the spade connections)

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Add teflon tape only to the threads on the new sensor and reinstall. Plug it in.
Top up coolant after you install the intercooler....the air bleed plug should be removed to let trapped air exit the system. Your're done!!! Simple.

This is some of the stuff I'll cover on our Calgary Delica Tech Night........we should do a webcast for Delica.ca! Who has web-savy and will be attending the tech night????

We might be doing ball joints and brakes that night! Fun stuff!

[islander20]

Great post, I have learned so much from this site all the helpful pictorials. Im about to setup a engine temperature sensor for an overheat alarm, would you recommend attaching the probe in the same location as the existing sensor?

On the topic of balljoints, do you know the average lifespan of the balljoints on the Delica? Im about to put a 2" lift on the van and am thinking about swapping out the balljoints while I am there. They were replaced 50,000km ago and aren't showing any weakness.

Thanks!

[stever1000]

Excellent write up!!

When would you recommend doing this?

[macro]

Great post, I have learned so much from this site all the helpful pictorials. Im about to setup a engine temperature sensor for an overheat alarm, would you recommend attaching the probe in the same location as the existing sensor?

On the topic of balljoints, do you know the average lifespan of the balljoints on the Delica? Im about to put a 2" lift on the van and am thinking about swapping out the balljoints while I am there. They were replaced 50,000km ago and aren't showing any weakness.

Thanks!

You could always replace them and keep your old ones around as spares. When I lifted mine, my balljoints went within the year because of the new angle.

Nice write up Big-Bird, very clear! My temp gauge is intermittently working again oddly enough...

[stever1000]

My thermostat was replaced last year, but no idea about the temp probe. Did your temp probe fail or why did you decide to change it?

[Big-Bird]

The temp gauge wasn't reading properly and the glow plug relay wasn't shutting off soon enough. Decided to do the change of both parts at the same time.

[FalcoColumbarius]

Excellent write up Big-Bird. I've loaded a copy of your post into L400 Dedicated Category Reference Forum >> Cooling & Oil ~ for convenient posterity, with a link back to the original thread (this one).

Falco.