Diesel inline thermostat mod and increase in MPG
 

I had time today to fit the inline thermostat to my 2.0 CDTi today, which I bought from Mat at DMGRS. Fitting it was pretty straight forward, even though as I don't have a Dremel, I had to remove the inlet manifold and attack the top hose clip with a hacksaw.

Once fitted, I put everything back together and took the car for a 100 mile drive out to Wisbech and back to see the inlaws. Amazingly after my previous personal best at Grandad driving (50.4 MPG) I managed an overall 55.4 MPG.

The engine is now running between 84 and 89 degrees (as opposed to between 60 and 64) and finally my heater blows warm.

I couldn't be happier with the results of such a simple modification.

Two things I did notice:

1. the inlets and EGR valve are covered with about 4mm of oily crud - is that OK / normal? Should I clean the EGR valve?

2. A narrow bore pipe leads from the front of the EGR to what I guess is whatever activates valve - the bracket that holds that gizmo has broken and it's flapping around under the ait intake duct. I guess I need to do something about that fairly quickly. I was thinking of cabletying it out of the way...

Cheers...

Simon.

A lot of members clean out the EGR and also fit a "by-pass"
You will find lot`s of info on here if you use the google search on the main page.
Ken.

Diesel inline thermostat mod and increase in MPG
 

That amount of crud in the egr is normal. Nothing at all to worry about but it really would benefit the car from giving it a good clean. You could then either refit and clean it every year or so or you could deactivate it by pulling off the vacuum hose and plugging the end of it. That would stop it building up more sludge. The other option as already suggested is to fit a bypass. This simply means removing the egr and replacing with a straight through pipe. I think Dmgrs sell them.

There's thoughts on both sides of the benefits of cleaning it or replacing it with a bypass.

As far as that loose bracket goes. They all seem to do that and cable tying is the way forward!


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Thanks for the replies, chaps.

I've just read the mammoth thread about the EGR Bypass:

http://www.the75andztclub.co.uk/foru...ad.php?t=12517

My conclusion based on that is that I think I'll remove it, clean it out and then refit. I'll do a few long journeys with the vacuum tube connected and then block it up temporarily and see if I can see any difference in performance and economy and make a final decision based on that. Certainly in the 20-or-so pages of the thread above, there didn't seem to be a clear answer either way.

Also I'm glad it's not just my car that has that failed bracket. Cable ties to the rescue!

I took it for another 120 mile run down to Leigh on Sea today and back, motorway driving on the way down and A-road on the way back. The 75 returned an indicated 52.3 MPG over the whole journey so I'm very impressed both with the improvement after sorting out the thermostat, but also with the car itself. It's like driving my Daimler in terms of ride quality and refinement, but with about twice the fuel economy.

It must be said that I'm getting those economy figures by driving differently to normal - very gentle acceleration and as little braking as possible but I did 70 mph where possible on the M11 and kept up to speed limits on the way back too. Not running the air-con and also having my tyres between 34 and 35 PSI both also must help.

Cheers for now...

Hey there,

Nah - the book pressure for the CDTi Tourer is 34 PSI - so mine are thereabouts. My pump doesn't have an accurate enough scale so I inflate them to just under the 35 PSI mark.

You've probably read it somewhere in the monster EGR thread you mentioned but when you get around to cleaning the EGR, do wear gloves and make sure you're not wearing anything that you will ever want to wear again. The crud gets everywhere and sticks like the proverbial to a blanket.

Well worth saying again though! Cheers for that :D

Glad you like the thermostat kit - it's usually the first thing I fit to a new 75/ZT entering the 'fleet'!
An EGR Bypass (and sadly, inlet manifold cleaning session) is usually the 2nd thing.

Toasty heaters just in time for winter... :)