Thread: oil cooler circuit 300tdi

Don't know the intricacies, but Mike at britannica restorations has a video on it's workings.
It fairly sure it shows that it's always closed and opens when a certain temp is reached.

My guess is that if it fails(ie. gets stuck) it would be closed, unless it's open at the time(of sticking) and therefore would get stuck open!

I have an oil temp gauge in in very high ambients oil temp can pass coolant temps.
On a drive out to Wilcannia area, it was in the low 40's. At the time I had some intermittent issues with coolant overheating.
From memory normal hot ambient oil temps were in the 70-80 range, but I was getting coolant up in the 100's.
Slowly oil started to follow(as you'd expect). Coolant temp issue was related to A/C on or off, so easy to manage.
Coolant would drop back down into the low 90s over a period, but oil temps would take a lot longer, and for a good time(say 30 mins or more) oil temp could be in the mid to high 90's but coolant would drop back down into the low 90's high 80's at the same time.
Longest continuous drive time I did was approx 2 hrs(maybe 1:59 or something).

I would reckon in Aus .. yeah, it's probably worth keeping it connected.

Turbo's certainly heat up oil. I wouldn't risk not having it operating.

Originally Posted by AK83

Don't know the intricacies, but Mike at britannica restorations has a video on it's workings.
It fairly sure it shows that it's always closed and opens when a certain temp is reached.

My guess is that if it fails(ie. gets stuck) it would be closed, unless it's open at the time(of sticking) and therefore would get stuck open!

I have an oil temp gauge in in very high ambients oil temp can pass coolant temps.
On a drive out to Wilcannia area, it was in the low 40's. At the time I had some intermittent issues with coolant overheating.
From memory normal hot ambient oil temps were in the 70-80 range, but I was getting coolant up in the 100's.
Slowly oil started to follow(as you'd expect). Coolant temp issue was related to A/C on or off, so easy to manage.
Coolant would drop back down into the low 90s over a period, but oil temps would take a lot longer, and for a good time(say 30 mins or more) oil temp could be in the mid to high 90's but coolant would drop back down into the low 90's high 80's at the same time.
Longest continuous drive time I did was approx 2 hrs(maybe 1:59 or something).

I would reckon in Aus .. yeah, it's probably worth keeping it connected.

Hi Ak83

Where do you have your oil sender installed?

Originally Posted by edddo

Just wondering - is this circuit even necessary? What would happen if it was bypassed or closed.
And if the oil thermostat fails - does it fail open or closed?

yes, and depending on what you;re doing almost critically so.

If its closed off, you cook the oil and it breaks down faster

The thermostat (IVe never seen one fail personally, housing leak Ive seen plenty of) in theory will fail closed, its just another variant of a wax plug thermostat like the one in the cooling system.

Originally Posted by travelrover

Hi Ak83

Where do you have your oil sender installed?

I got oil pressure and temp gauge(s)

Removed the warning light sender, installed a two plug adapter, added another twin plug adapter to the closest port for pressure sender unit too. So adapter onto adapter kind of setup.
A bit clunky, and if needed to remove has to be done ins specific order due to limited rotational space. Not ideal, but could never find an adapter with 3 ports(instead of two) to fit.

I did think to self, why keep the warning light sender unit when I have a pressure gauge, but the adapters were cheap enough and not hard to daisy chain, so why not.
VDO sender units running to a 1Gauge unit.

Originally Posted by BathurstTom

Turbo's certainly heat up oil. I wouldn't risk not having it operating.

Yeah, this is true, but also the V8s have them too.
My guess is more likely that in off road/arduous conditions, keeping oil a little bit cooler is better than allowing it to get way too hot.

Another reason could be capacity design too.
IIRC my old mans 60 series had something like 11 lt sump or something mad like that. I don't remember any oil cooler(may have, just can't remember it).

Originally Posted by Blknight.aus

yes, and depending on what you;re doing almost critically so.

If its closed off, you cook the oil and it breaks down faster

The thermostat (IVe never seen one fail personally, housing leak Ive seen plenty of) in theory will fail closed, its just another variant of a wax plug thermostat like the one in the cooling system.

Thanks - are these standard in UK vehicles as well or an addition to Aus spec for hotter running conditions?

I ask because this circuit is a source of irritating oil leaks of various kinds..and clearly because of what it is - a reliability factor with possible catastrophic results.