over heating issue

[Shayward]

Hi all
I have recently installed the rebuilt 300tdi. After a thorough check, fired it up and it all seemed well. idled for a good half hour, pre flight checks, all good. First run and after a hill overheated. Topped up water but still issues and no heater. Figured we had an air lock. Followed all good advice on this forum, thought I had it sorted, still over heating. In short, it will idle all day, no heat in heater though. Give it a run and the heater will kick in eventually for a short time and then stop again. Shortly thereafter temp climbs and I stop before I have a bigger problem. No sign of oil in water or vice versa so I am hoping have not caused an issue with first hot spell.( pressure from head gasket etc ) Thought I may have left a rag in the system as I used a few to plug things up during the rebuild. Pulled the thermo housing and water pump housing off again and flushed system. No obvious blockages. The bolts were not super tight. Have checked thermostat and in fact replaced, also new water pump. My current thinking is sucking air around pump / thermo housing or radiator cap not working properly. I don't have gear to test this. before I give up and drop down to specialist any advice? thanks in advance. Shaun

[Boony73]

Is your viscous coupling working?

[Shayward]

Fan all looks good. I thought about it but if the fan was stuffed then we would see heat through heater as temp rises? heater is cold even with temp gauge coming up and then I have had a burst of warm / hot air before losing it again. that is why I was thinking blockage or air lock. take it for a drive and put under load and then temp rises pretty fast
thanks for the suggestion

[Tank]

Fan all looks good. I thought about it but if the fan was stuffed then we would see heat through heater as temp rises? heater is cold even with temp gauge coming up and then I have had a burst of warm / hot air before losing it again. that is why I was thinking blockage or air lock. take it for a drive and put under load and then temp rises pretty fast
thanks for the suggestion
You should never ever let a newly rebuilt engine (or an old one for that matter) idle for as long as you have stated, you may have glazed the bores by doing so, a new engine needs to be run and worked to bed the rings into the bore.
As far as overheating goes, this is what I do to avoid air in the system.
First remove the 2 plugs, one in top of rad. and the other in the Thermostat housing.
Turn the heater controls up to max..
Fill through the header tank till coolant flows out of rad. top, fit plug while coolant still running out top.
Then fill from top of thermo. housing, when full replace plug .
Take it for a drive and drive it like you stole it for at least 1/2 an hour, park it overnight and check coolant level, top up if necessary.
Might pay to check before doing above that the 3 way T-piece is not blocked, it is near the header tank with the small hoses that come from the thermo housing/ rad. to header tank, good luck, regards Frank.

[Shayward]

Thanks Frank, have replaced T piece and about to check the cap. it will be a weekend job now as my week is shot.
cheers