Bongo Fury

Basically, van is getting to temperature where the thermostat should open but bottom hose remains cool and this time the radiator fans have kicked in. I have a self bleed kit installed and this is the diesel engine. Read on for the specifics which may answer some of the things you are already thinking about

OK so I've replaced the water pump, thermostat, both alternator belts and aircon belt this week. I've also bypassed the rear heater matrix due to the sorry state of the metal pipe.

I drained, flushed and refilled the system and bled it pre any of these changes, all ok and bottom hose got warm. Then did all the above changes, checked new thermostat opens in a pan, it did, when i removed the old one I did the same and it did so it was obviously ok but replaced it with the working new one anyway.

Since then I flushed it again using holts speedflush to ensure all could be clean as I could get it, this involves adding 250 ml of the holts to the system with water, bleeding it, getting up to idle temperature (which it did and again bottom hose got hot) then 10 minutes of fast idle, let it cool and drain it.

so i let it cool over night, drained this morning and have just added 50:50 Halfords OAT and distilled water via the coolant tank and have followed what ive done previously, however, this time where the thermostat usually opens at about 87 degrees and the bottom hose opens, this time its gone to 90, not opened and the radiator fans have now kicked in keeping it cool and bottom hose is cold.

So, I've halted proceedings for fear of doing damage to the head.

So, either Im figuring Ive had bad luck this time and theres an air bubble trapped somewhere or the rad fans are keeping the rad too cool to open the thermostat and I guess I should disable them?

Any help would be appreciated.

It does sound as though you do have an air lock in there as no other overheating problems are current. if you can I'd do away with the self bleeding system and revert back to the 3 part video found on here. bleeding air out on my diesel (96) takes between 40 minutes to an hour and can't be rushed it really can't. the benefit of not using the self bleed kit is that you partially bleed the system using the up and down funnel technique before you even start the engine.

Hmmmm was afraid it wouldnt be a fan thing, needed to hear it from someone though I guess.

I don't think that the self bleed kits the issue, it's been fine so far. I may have just rushed it this time and the only other thing I did differently was filling from the coolant tank only with rad cap off until the water came out of it then put rad cap on and carried on filling via coolant tank.
Whereas other times Ive filled rad up first, I might drain and refill again.

Never understood how that self bleed causes the air to come out of the engine! The 2l petrol is a different engine to the diesel and V6 less likely to trap air inside. The whole process on the video's is about getting a surge of pressure thru the engine to help expel the air, the self bleed kit only bypasses the section outside of the engine, but then the that is what the normal bleed tube is about anyway.

drained and rebled again this afternoon and all went perfectly this time, bottom hose nice and hot, no fans, highest temp was 88 which is what Ive always seen before.

Must have been the way I filled it that one time which is weird but there was nothing different I did.