Engine, Type 4, 2 ltr, twin weber had low compression on number 3 cylinder. Specialist suggested a dropped/burnt valve but it's worse - the head has cracked. A new head has been ordered from Heritage. The specialist thinks the thermostat may not have been opening fully as the cause and has suggested jamming the flaps open (by not fitting a new thermostat) as I don't want a repeat on the new head. Is this a good idea - I think it may be and am prepared for a longer warm up/slightly worse fuel consumption or does anyone have a different solution? There is currently no tinware underneath the engine. Thanks. Jeremy
You need the bottom tin for the thrmostat to work properly, so rather than abandon the thermostat, why not fit the tin?
Thermostats of T4s fail open? Sounds unlikely to me but someone with more knowledge than me will be along presently I am sure. I have heard it said that air leaks on the brake servo circuit can cause cylinder 3 overheat. By the way Paul Weeding on here does the under engine tin in fibreglass (its rocking horse poo to find OG)
I've run a T2 1800 with no thermo. for three of four years now. I had an old time VW guy tell me to "pin" the flaps 1/2 open and shut with a screw through the flap that "stands" on the edge of the tin to keep it open. I've had no issues with over heating. I do have the "under tin" in place though.
I have more faith in VW engineers. Not an expert on T4 engines but , worth testing the thermostat - put it in fridge for 10mins, measure the height then boil a kettle drop it in a cup with said hot water, leave it in for a few mins, it should expand, if not then its stuffed. Fins and tinware must be inplace and please dont use that cheap aftermarket chrome type tinware use boring black stuff,its there for a reason. Its likely your cylinder heads are just old and suffered fatigue (assuming its old?)
If you don't have the under tins, then the thermo won't open properly as the air flow, under the van, when driving will cool the thermostat!!
There's a guy on VZi selling MASSES of tinware at the moment. http://www.volkszone.com/VZi/showthread.php?t=1136001
VW fixed the weakness of the T1 alloy cases by using aluminium engine cases on the T4, so one of the next weaknesses exposed is the T4 engine cylinder head and its ability to get overheated. This is why the Americans get fixated on the Cylinder Head Temperature - fitting a second gauge to their T4 setups to monitor the temperature with a sender bolted down under a sparkplug. and back off quickly as the CHT changes very rapidly. I think its also because there are a lot of pilots in the USA using VW derived engines where the CHT is a major indication of the engine fuel/air mixture. So they can buy a 4 cylinder head temperature setup intended for an aircraft engine. I think also that fitting a Air Fuel Meter (wideband lambda sensor etc) can also warn you that the engine is running lean and possibly hot under load and tells you to re-tune it richer or clean out the jets. If it is running rich it may also run hot just it tends to run smoky and you notice it.
Thanks for all the replies. I'll get some under tins. I trust this specialist as he was a foreman in a VW dealership, cut his teeth as an apprentice on air cooled stuff and more importantly came recommended by other air cooled owners. His orignal thinking was an air leak but that wasn't apparent, but Paul's suggestion that a lack of under tinware may cause unintended cooling of the thermostat may be the reason. Jeremy
Disabling the thermostat cooling system will shorten the life of your engine. No ifs, no buts. If he's such an expert he should know better.
If you trust this guy why are you asking for advice ? Screwing flaps so they are half open is pure madness so is not running a thermostat , fit as vw intended ...thermostat ,under tin ,flaps
lhu1281 - to answer your question, simply because I like to be as informed as possible and this forum provides some really helpful and useful advice. 'Underwear' now prchased and thought being given to getting hold of a cylinder head temperature thermocouple/sensor and gauge and new thermostat. VDO don't seem to fare too well - has anyone any experience of one of these http://www.ebay.co.uk/itm/Cylinder-...arts_Vehicles_CarParts_SM&hash=item2592a7ab47
Have a read on Ratwell site about cht gauges. I bought a dakota digital on his advise and an very pleased with it. I know lots will tell you it's a worry gauge, but it allows you to keep an eye on your engine. Always suprised how hot it can get on a long climb (living on Dartmoor, no shortage of hills ) but gauge will tell you when to back off and change down.
