Coolant change experience
Posted: Sun Nov 30, 2008 8:04 pm
I'd seen from some old reciepts that our recently purchased '96 had a new top hose two and a half years ago, this probably being the last time any new coolant was put in.
So this week I've changed the coolant, and the experience has raised some questions that I hadn't seen the answers to on these forums.
I researched the procedure, looked at parts diagrams etc and I followed the fact sheet (again, thanks for producing these
) and used method No 1 to bleed the system.
What initially surprised me was that after draining the radiator when I took the top hose off I found it to be empty, and when water was poured into it the water came out of the radiator plug. I have since found out that there is a "by-pass" system (that explains the small bore pipe going into the bottom of the rad). So if your Bongo has the by-pass system then there is no need to take off the top pipe.
After draining and flushing (as much as I could without access to a hosepipe) I refilled with coolant. I tied a bucket to the handbrake and hung the bleed hose onto its rim. When I started the motor about 1 Litre of coolant was ejected from the bleed pipe, and the expansion chamber needed a little topping up. During the 10 min "idle phase" the level in the expansion chamber increased slightly and there was no coolant loss through the bleed hose. When the revs were increased for the next phase there was only a little loss through the bleed hose, with a subsequent drop in the expansion chamber. It took about 20 mins (rather than the 6 to 9 mins) for the thermostat to open (warm bottom hose), and again, there was only a small ejection of (hot) coolant from the bleed hose.
At this point the fact sheet suggests that both bleed hose and expansion chamber are now closed and a rev/idle sequence is followed. I did this, but thought it odd and wonder whether the bleeding process can continue with the bleed hose closed?
After putting the engine undercover back on (which doesn't need to come off BTW) a test drive seemed to indicate all was well. After cooling down (next day) aprox 1 litre was needed to top up the expansion chamber.
But, as a born worrier, I wondered whether the bleeding had been successful?
So this weekend I've tried the seesaw method as a check.
With a cold, dead engine I conected a funnel to the bleed hose and hung it off the door frame. I filled the funnel with quite a lot of coolant, and it wasn't until I heard the splashing that I realised the expansion chamber was overflowing
. I adjusted the height of the funnel to that of the chamber and idled the engine for 10 mins. At no time during this idling did any bubbles appear in the funnel or chamber.
I then needed assistance to rev the engine and juggle funnels etc. My idea was to warm the engine up enough to open the thermostat (took 20 mins last time), but every time the revs were increased the level in the funnel dropped, and the level in the expansion chamber increased. Letting the engine idle again returned the coolant levels. So no additional coolant needed adding. But I could only rev the engine for 5 to 10 seconds at a time (didn't want to "suck" air in through the bleed hose). I could increase the rev time to about 15 seconds by lowering the funnel. Consequently it took well over half a hour to get warm.
Eventually the bottom hose got hot. But still no air bubbled up through the funnel or chamber. So I'm guessing the system is fully bled, and indeed was fully bled the first time!
But the worrier in me is now concerned by the funnel coolant level dropping whilst reving the engine. Does this mean that there may be a blockage somewhere? Am I worrying needlessly?
So thanks again to all the threads I've read on here regarding coolant changes, and of course the fact sheets (along with their discrepencies
) for giving me the confidence to charge in there and get it done.
So this week I've changed the coolant, and the experience has raised some questions that I hadn't seen the answers to on these forums.
I researched the procedure, looked at parts diagrams etc and I followed the fact sheet (again, thanks for producing these
) and used method No 1 to bleed the system.What initially surprised me was that after draining the radiator when I took the top hose off I found it to be empty, and when water was poured into it the water came out of the radiator plug. I have since found out that there is a "by-pass" system (that explains the small bore pipe going into the bottom of the rad). So if your Bongo has the by-pass system then there is no need to take off the top pipe.
After draining and flushing (as much as I could without access to a hosepipe) I refilled with coolant. I tied a bucket to the handbrake and hung the bleed hose onto its rim. When I started the motor about 1 Litre of coolant was ejected from the bleed pipe, and the expansion chamber needed a little topping up. During the 10 min "idle phase" the level in the expansion chamber increased slightly and there was no coolant loss through the bleed hose. When the revs were increased for the next phase there was only a little loss through the bleed hose, with a subsequent drop in the expansion chamber. It took about 20 mins (rather than the 6 to 9 mins) for the thermostat to open (warm bottom hose), and again, there was only a small ejection of (hot) coolant from the bleed hose.
At this point the fact sheet suggests that both bleed hose and expansion chamber are now closed and a rev/idle sequence is followed. I did this, but thought it odd and wonder whether the bleeding process can continue with the bleed hose closed?
After putting the engine undercover back on (which doesn't need to come off BTW) a test drive seemed to indicate all was well. After cooling down (next day) aprox 1 litre was needed to top up the expansion chamber.
But, as a born worrier, I wondered whether the bleeding had been successful?
So this weekend I've tried the seesaw method as a check.
With a cold, dead engine I conected a funnel to the bleed hose and hung it off the door frame. I filled the funnel with quite a lot of coolant, and it wasn't until I heard the splashing that I realised the expansion chamber was overflowing
. I adjusted the height of the funnel to that of the chamber and idled the engine for 10 mins. At no time during this idling did any bubbles appear in the funnel or chamber.I then needed assistance to rev the engine and juggle funnels etc. My idea was to warm the engine up enough to open the thermostat (took 20 mins last time), but every time the revs were increased the level in the funnel dropped, and the level in the expansion chamber increased. Letting the engine idle again returned the coolant levels. So no additional coolant needed adding. But I could only rev the engine for 5 to 10 seconds at a time (didn't want to "suck" air in through the bleed hose). I could increase the rev time to about 15 seconds by lowering the funnel. Consequently it took well over half a hour to get warm.
Eventually the bottom hose got hot. But still no air bubbled up through the funnel or chamber. So I'm guessing the system is fully bled, and indeed was fully bled the first time!
But the worrier in me is now concerned by the funnel coolant level dropping whilst reving the engine. Does this mean that there may be a blockage somewhere? Am I worrying needlessly?
So thanks again to all the threads I've read on here regarding coolant changes, and of course the fact sheets (along with their discrepencies
) for giving me the confidence to charge in there and get it done.