Bongo Fury

Can anyone help Ben?

"I have a 2.5 Diesel, N reg and I am based in Notingham. New cam belt has been fitted and the engine starts straight off the turn of the key and sounds great but one thing. I keep filling up the water as we think there is an airlock. When I drive up to 50 mph the orange coil light on the dashboard flashes and when I stop the engine the fans or something keep turning over for about 5 minutes or so. My mechanic said he is going to get a special bleed tool which creates a vacuum but I just wanted to check with you in case it could be something else. I am driving to Cornwall in a week so need to sort. Thank you for your time"

I suppose we really need a bit more info, was anything else done when the timing belt was changed ?? ie was the cooling system disturbed ?
If the system has air in it there must be a reason. unless we know that the cooling system was disturbed when the work was done then bleeding the cooling system probably wont help long term. Need to first find out where the coolant is going.

Second that.

What makes him think he has an airlock?

Presumably he is topping up because coolant level dropped. How low has it got, below low mark, down to black pipe?

Definitely bleed the system to get it to a known good state. Then test and monitor. Does level drop slowly over time or is it ejected when engine hot. Test for gases in coolant. Pressure test cooling system.

LCA or extra temp sensor fitted? If so what are they saying?

No need to interfere with cooling system for cam belt change but maybe either coincidence or something disturbed.

to quick check for airlocks,

with the engine not running squeeze hard and quickly the top hose out of the head, listen for the air moving about, squeeze the bottom hose from the rad back to the stat housing, again listen for air moving, if its full you may hear the jiggle pin clicking on the thermostat, it wont click if air is present here, it will click if the water is lifting the jiggle pin as it is a float when the water hits it it shuts.

to check for air in the heaters you either loosen a clip on each side of the heater unit/s or run the engine to see if they get hot (this has obvious risk to the head).

dont ignore the fact that the fans are coming on, this is saying the sensor is either faulty, the wire has been knocked or bad connection, or the sensor end has broken, or its doing its job ----- its hot.

in my experience the vac fill system is not always successful in removing all the air, the vac will pull in coolant via the easiest (not blocked route) and may leave air in the harder to pull through routes.

If you have the air conditioning on the engine fan will run .. but on the diesel I believe the coil light coming on indicates it's the scavenger fan that's cutting in ..

From your comment ...." My mechanic said he is going to get a special bleed tool which creates a vacuum" ... I assume it is not a garage job as most would have a Vacuum / purge kit to hand ..(even as a 100% amateur I have) ..



Did he change the water pump as part of the cam belt job .. ??

Or maybe the strain / tension on the old water pump shaft fitting the new belt as allowed air to pass the seals into the coolant system ..??

Sorry to hear your problems. The only thing I can add....after a recent overheat I was asked to feel the top hose before starting the engine and gauge it's "feel". Once you have gauged the feel run the engine from cold and hold the top hose again and see if it has become harder. Apparently this can take from 30 secs to 3 mins so keep checking it. If it swells and hardens exhaust gasses could be entering the cooling system.

I have never seen my coil light come on when the scavenger fan came on recently 2.5D here. (But then the Bongo was clearly not well at this stage)

All seemed ok as far as my hoses.

Unfortunately despite checking the hoses myself before the Bongo went to a reputable garage. It turns out with a new thermostat and rad + rad fan switch that when the system had reach 80C+ something odd started happening. Spitting fluid out of expansion tank and scavenger fan whirring and sadly pipes hardening suggesting either gasket or head has blown/cracked. It is still being diagnosed I have not heard anything for a while. So the basic from cold test seemingly does not guarantee there is no problem but it seems to be the first thing to check as others have mentioned.

Good luck.