Air getting into coolant system
Posted: Thu Jun 08, 2017 9:45 am
Hi community 
I have a problem with my coolant system, here's the story:
Coolant was leaking on to the floor, on inspection I found a split coolant hose under the passenger seat (the 's' shaped one that goes from the metal heater pipe to near the alternator/turbo).
I replaced that pipe and the bottom radiator hose as I had previously bought this in error anyway.
I refilled the coolant system and bled it using the see saw technique, but it took a lot longer than usual to achieve no bubbles in the funnel. Eventually we got there after about an hour and a half.
After finishing the bleeding process, the coolant level in the header tank dropped whilst I was tidying up, so i topped it up. After a few days and 2 short journeys I noticed the temp gauge fluctuating so I pulled over. There was coolant under the engine but I couldn't spot the leak. I tried to find the leak by topping up the coolant and leaving the engine running but couldn't see anything. I gave it some cycles of revs but still couldn't see anything, the temp gauge eventually went up and heaters were blowing cold air, so it appeared air had entered the system.
I topped up the water again then left the van for a few days, when I returned the header tank was almost empty, so I topped it up and tried bleeding it again. Without the engine running there were no bubbles. Started the engine and did the see saw technique for 45 mins (without revving the engine), but the bubbles persisted. The heaters were blowing hot air now. Tried revving the engine and the bubbles got more intense and then started spluttering vigorously so I turned the engine off. Without the engine running there were no bubbles when see sawing. During the whole process there was still no evidence of a leak but then it was difficult to tell because the ground was wet anyway.
I will return to the van today to see if the coolant level has gone down again whilst being sat there.
The other thing to mention is that I have had a milky white substance on the underside of the coolant header tank cap for quite a while, which maybe suggests oil is getting into the water? I also noticed this slime on the inside of the metal heater pipe when I replaced the hose. The oil level is relatively stable and there is no white slime on the oil cap. My theory is that air and/or oil is entering the system somewhere. A friend suggested there could be a leak in the oil cooler, if there is such a thing on the bongo?
Does this sound like a cracked cylinder head or something like that? I was considering taking it to my local approved bongo garage to see if they can spot a leak that I can't. The guy I bought it off did say he had something cylinder-related replaced (possibly the head, is that possible? Forgive my lack of understandig of engines!), but I can't remember what.
It's a 1996 with a few other problems but Ive just spent £800 getting it welded for the MOT so desperate to try anything to stop it being written off. Any advice/suggestions greatly appreciated.
Thanks very much in advance!

I have a problem with my coolant system, here's the story:
Coolant was leaking on to the floor, on inspection I found a split coolant hose under the passenger seat (the 's' shaped one that goes from the metal heater pipe to near the alternator/turbo).
I replaced that pipe and the bottom radiator hose as I had previously bought this in error anyway.
I refilled the coolant system and bled it using the see saw technique, but it took a lot longer than usual to achieve no bubbles in the funnel. Eventually we got there after about an hour and a half.
After finishing the bleeding process, the coolant level in the header tank dropped whilst I was tidying up, so i topped it up. After a few days and 2 short journeys I noticed the temp gauge fluctuating so I pulled over. There was coolant under the engine but I couldn't spot the leak. I tried to find the leak by topping up the coolant and leaving the engine running but couldn't see anything. I gave it some cycles of revs but still couldn't see anything, the temp gauge eventually went up and heaters were blowing cold air, so it appeared air had entered the system.
I topped up the water again then left the van for a few days, when I returned the header tank was almost empty, so I topped it up and tried bleeding it again. Without the engine running there were no bubbles. Started the engine and did the see saw technique for 45 mins (without revving the engine), but the bubbles persisted. The heaters were blowing hot air now. Tried revving the engine and the bubbles got more intense and then started spluttering vigorously so I turned the engine off. Without the engine running there were no bubbles when see sawing. During the whole process there was still no evidence of a leak but then it was difficult to tell because the ground was wet anyway.
I will return to the van today to see if the coolant level has gone down again whilst being sat there.
The other thing to mention is that I have had a milky white substance on the underside of the coolant header tank cap for quite a while, which maybe suggests oil is getting into the water? I also noticed this slime on the inside of the metal heater pipe when I replaced the hose. The oil level is relatively stable and there is no white slime on the oil cap. My theory is that air and/or oil is entering the system somewhere. A friend suggested there could be a leak in the oil cooler, if there is such a thing on the bongo?
Does this sound like a cracked cylinder head or something like that? I was considering taking it to my local approved bongo garage to see if they can spot a leak that I can't. The guy I bought it off did say he had something cylinder-related replaced (possibly the head, is that possible? Forgive my lack of understandig of engines!), but I can't remember what.
It's a 1996 with a few other problems but Ive just spent £800 getting it welded for the MOT so desperate to try anything to stop it being written off. Any advice/suggestions greatly appreciated.
Thanks very much in advance!