Maverik 211 Posted April 27, 2015 Just replaced the gasket and housing on my Def 200Tdi as per other post, but on my quest to get the best out of the cab heater, when I was fettling the engine last summer I noticed that the water take off from the thermostat housing to the heater (vie the cylinder head pre heat pipe) the actually hole from the thermostat housing is quite small and almost obstructed... so I purchased another housing and planned to make the heater pipe outlet larger... after some more thinking and engine fettling I found that just by putting slightly larger pipework to the heater made a massive difference to heat output, going along the same lines rather than outrageously enlarge the stub piece, I found that just by running a 10mm drill bit down the hole cut away the restriction that you can see when you look down it. Anyhow here's what I did the one on the left is factory, the one on the right is after I ran the drill bit down it. I thought long and hard about any consequences to the rest of the cooling system for me opening it up a bit, but couldn't think of anything directly other than a less restricted flow of water to the cab heater. Its will probably be difficult to quantify the improvement, but just putting it out there. Mav Share this post Link to post Share on other sites
Bowie69 563 Posted April 27, 2015 Gotta help with flow lots, if you wanted to be even more fancy you could chamfer/smooth the edges of the hole too Share this post Link to post Share on other sites
Mo Murphy 292 Posted April 28, 2015 Mav, so which pipes did you enlarge that made such a difference and by what amount ? I take it from your write up that it made a tangible improvement ? Mo Share this post Link to post Share on other sites
Maverik 211 Posted April 28, 2015 Hey Mo, I swapped out the two pipes that go from the heater to the engine, simples, they where what I believe to be original era too i.e. 1986 I'd never paid much attention to them until one day one looked like it was slightly narrowing, so I had a couple of pipe taken from a D1 which are somewhat wider in diameter, with a bit of fettling and cutting I got them to fit (but I've also got my Webesto heater plumbed in now - which confuses things a bit but not much). The difference was HUGE (for me) I might have been deprived of cab heat before so its all relative... but the whole process got me thinking about narrowing of the heater circuit anywhere along its system hence the above wee mod. When I had the Camel 110, that thing used to put out an amazing amount of heat, I did a small experiment where I mounted a thermocouple in the driver side windscreen blower duct, I started engine from cold a drove the same circuit twice, with my truck and the Camel, I found that there was just shy of 20 degree temp difference between it and my 90 (90 being the colder one), that started the quest for improvement. So after changing the pipes its difficult for me to measure the improvement as I don't have the Camel anymore, but during this past winter I didn't need a thermocouple to tell me I'd found one of the reasons for lack of heat. Share this post Link to post Share on other sites
Mo Murphy 292 Posted April 28, 2015 Ok Mav, good call with the thermostat housing though. I'll have a look at mine next time I change the thermostat. Mo Share this post Link to post Share on other sites
