Have you got the little flaps in the system - parts 41 and 42? Very little air goes forward from the engine fan at idle so the electric fan is needed to boost it. But without the flaps air will back up the wrong way. Are the main control valves opening fully - the ones controlled form the cab? Also there's some flaps in the electric fan itself.
Exactly that! I used the technically innovative method of sticking gaffa tape over the stove pipe tops. The T4 engine fan does enough work to be able to feel it at windscreen end, turn the bilge blower on and you can't hold your hand over the vent too long! I too mounted the bilge blower as far for'ard as possible. (see what I did there?) So far, no melty melty.
Are your heater control cables definitely operating the flaps at the top of the riser pods correctly? Sounds like they are shut to me!
I'll give your suggestions a check in the next few days. I'm pretty sure the main flaps work from the cables but I'll definitely check the other flaps 41 and 42
You'll struggle to check 41&42 with the engine in situ, even if they're missing it wouldn't stop air getting to your screen if everything else is in order, neither would having no snail fan or thermostat!
Not that difficult actually; if you get the tin off above the silencer, you'll see two removable covers (part 26). But I admit lack of these flaps will only be a problem if you are finding that the electric fan is not having much effect at idle.
Your tubes are blocked then. The main one down the middle - does it have an insulating wrapper round it? I took the wrppaer off mine and there was no longer a steel tube inside - just a 2" x 6" shard. The rest was flakes of rust. Further up the tube was blocked for several feet with mouse nest stuff. A good carrier bag full. This is normal, particularly if it came from the USA.
Yes it does have the insulating wrap, it is from the USA. The tube is a bit crusty when I press it so I suspect your right Zed. What's the cure....weld a new one in or do a DIY ducting job?
Either, and after welding a couple in, DIY ducting is often easier - twin walled waterproof duct is available on ebay. It depends what you find. The last one I did still had + 6" either end so slipping a bit of flexible ducting on was a no brainer in terms of time. Same result.
