CDTI - low operating temperature?

[Workhorse]

Hi all,

I finally got round to working out the dashboard diagnostics on my 2004 75 diesel so that I could see what was going on with the engine temperature. The temperature gauge has always looked on the low side, but I wasn't sure if that was just the gauge under-reading.

Basically, the temperature initially goes up quite rapidly, which would indicate to me that the thermostat is working as it should at least initially. However, after mixed driving the needle only goes about of a third of the way up the dial, which I now know equates to about 70 degrees, so on the low side.

I'm assuming this means I need to look at my thermostat, but I'm just a bit confused that it's initially picking up temperature fine, but it's not getting to the 90 or so degrees I'd expect to see. Is it a case that it's opening a bit too early?

Any thoughts welcomed!
Thanks all

[T-Cut]

To use a well trodden phrase, they all do that. The cause is almost always due to the way these thermostats deteriorate. They start opening earlier and prevent a normal running temperature to be reached. Diesels run pretty cool anyway, but with a properly operating thermostat, it will reach the 85-90C you want. The most popular/easiest/cheapest fix is the inline stat modification.
Some reading: https://cse.google.com/cse?cx=013872...85.H6tDMLnO4gQ


And the correct brand is important.


TC

[DMGRS]

As TC says, very common - over the years we've been working on perfecting the various solutions thrown around for this problem.

First up, easiest - the inline thermostat in the top hose. We offer a kit for £9.99 that includes instructions, a thermostat we know works well and hose clamps - everything needed - https://www.dmgrs.co.uk/collections/...tat-89-degrees

If you'd rather change the original, we offer a 'V3' thermostat which is designed to avoid the original mode of failure - here: https://www.dmgrs.co.uk/products/r75...evised-version

Finally, I had to do the job myself with the V3 - so I wrote a bit of a guide here including a bit more info on each option, and a How To guide for fitting it:
https://the75andztclub.co.uk/forum/s...d.php?t=164968

[Workhorse]

Okay great, thanks both. I'm about due a big service so I'll add a thermostat to the list. I've seen the inline modification, but I'll probably have the original changed as I know it'll annoy me knowing the faulty one is still there!

[marinabrian]

Originally Posted by Workhorse

Okay great, thanks both. I'm about due a big service so I'll add a thermostat to the list. I've seen the inline modification, but I'll probably have the original changed as I know it'll annoy me knowing the faulty one is still there!

It's a three hour job to change the original, and the new one will go the same way.

Compare that to a fix for less than a tenner and fifteen minutes to carry out, both of my diesels have the Renault 5 thermostat fitted

Brian

[clf]

Originally Posted by marinabrian

It's a three hour job to change the original, and the new one will go the same way.

Compare that to a fix for less than a tenner and fifteen minutes to carry out, both of my diesels have the Renault 5 thermostat fitted

Brian

Wahler 3029.89 fitted 4-5 years ago, and still maintaining 86 degrees without issue now. I am surprised, to be honest. It is a bodge, but such an effective bodge it has to be called a fix really.

[BoroRover]

Originally Posted by marinabrian

It's a three hour job to change the original, and the new one will go the same way.

Compare that to a fix for less than a tenner and fifteen minutes to carry out, both of my diesels have the Renault 5 thermostat fitted

Brian

As ever, sound advice. My diesel was running cool...thermostat. Fifteen minutes after Brian turning up, job done, instant fix, fine ever since. What's not to like ?

[Workhorse]

Okay so I didn't quite appreciate how involved changing the original is, so I'm coming round to the inline mod- I'm assuming that the difficulty with the original is simply down to access?
I think a new clutch will be needed in the not too distant future, so is the original item something that could be replaced relatively easily at the same time?

[Daveluck]

Originally Posted by Workhorse

Okay so I didn't quite appreciate how involved changing the original is, so I'm coming round to the inline mod- I'm assuming that the difficulty with the original is simply down to access?
I think a new clutch will be needed in the not too distant future, so is the original item something that could be replaced relatively easily at the same time?

So...just my opinion as I'm somewhat hamfisted.

No!

The thermostat change is a pig of a job unless the engine happens to be sitting in a cradle or on a bench. It's fiddly and prone to being messed up by bending pipes and pinching o rings...and there is no guarantee the thing will operate as expected.

I've had a new thermostat in a drawer in its packaging for approx 3 years and that is where it is going to stay.

So unless it's leaking leave it alone and go with the R5 solution.

As an aside...have we had any reports on the longevity of the V3 thermostat? Matt?

[Mike Noc]

Originally Posted by Workhorse

I think a new clutch will be needed in the not too distant future, so is the original item something that could be replaced relatively easily at the same time?

Sadly not - it is on the other side of the engine to the gearbox.

The inline stat is a very easy fix, but as mentioned the thermostat housing seal and coolant pipe O ring can leak over time, and you can renew both of these if you replace the original stat.

The original water pumps are very good. Mine almost made 300k miles before it bought the farm - better than a K Series any day of the week!








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