Air getting into coolant system

[djfairbrother]

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!

[Northern Bongolow]

where is your rough location.
you need to establish if there is a leak or not before bleeding as you could be wasting your time.
fill the system with water or coolant then i fit a car tyre valve to the overflow black pipe on the expansion tank, get a foot pump with a tyre pressure gauge on it and inflate the system to no more than 1 bar, most leaks are then very obvious especially if you fit a pressure gauge into the end of the bleed pipe and watch the pressure drop.
there are some harder to see leaks these are the water pump and the head crack.
once you get it air tight you may find that it bleeds up easier.
you could take it to a bongo specialist to do a positive pressure test, but most will do a vacuum test, this doesnt always show where the leak is or even if it has one due to the vac pulling the leak closed if its on a pipe joint.
dont drive it far until you have got it air/water tight.
good luck.

[djfairbrother]

Thanks very much!

Are the car tyre valves easy to fit to the overflow pipe? And the pressure gauge to the bleed pipe? Would I do all that with the engine off and cold, yeah?

Im in Newcastle. Nearest bongo specialist is 15/20 mins drive. Do you think that would be too far? If they can do a positive pressure test would that achieve the same as the DIY solution you suggest?

Thanks loads for your help!

[Northern Bongolow]

just go round the bin at your local ats etc, they cut them off when they fit new tyres. get a knife and pear back some of the rubber stem so that it fits tight in the pipe, its rubber to rubber so grips well. do it with the engine cold and off.

15 20 mins might just be 1 min too long, but its your shout really, i would ask them to tow it in.

[haydn callow]

If you have a old push bike innertube ( high pressure type) you can hacksaw the valve off, that also Does the job.

[djfairbrother]

Thanks for your help guys.

Inflated the system and found the leak, it's on the t piece at the end of the metal O/S rear heater supply pipe, where there's been a horrible bodge with tape and putty at some point in the past.

Local bongo garage have quoted £110 to replace and bleed, new pipe and hoses are going to cost about another £100. Being as skint as I am, is it possible to cut out the t piece and replace with a DIY version using a standard copper pipe connector (friend suggested this), or does this just sound like a terrible idea?

How difficult is it to replace the metal pipe and connecting hoses myself? I'm certainly well practiced in the bleed process now!

Thanks again for all your help...

[haydn callow]

Yep ,, you can do as you suggest.....use proper hose to make connections. It is a bit of a bodge and you will have another half dozen rubber/metal joints to possibly leak.
Treat it as a short term fix

[cmm303]

Hoses are reasonably easy to replace.
One of the metal pipes to the rear heater snakes its way to the front and is a fiddle to replace - never done it myself but from looking at the vehicle and reading here it would need a bit of dismantling.

[Northern Bongolow]

have a read of this,

http://igmaynard.co.uk/bongo/forum/view ... =3&t=58378

[djfairbrother]

Thanks all. On my way to the garage, stopping every 5 mins to allow engine to cool! Ordered new steel pipe and hoses in the end.

[Muzorewa]

While they're at it, get them to look at the steel ATF pipes running gearbox oil to & from the radiator, those pipes are in the same vicinity as your coolant pipe and if they're similarly corroded you may as well get them done while the vehicle is in bits. It may have been the subject of a similar previous bodge but you wouldn't want to spring a leak there shortly after having sorted the coolant leak

[djfairbrother]

Thanks for the advice, I'll ask them to take a look.

[cmm303]

I know the list goes on .... (I received this advice last year and went weak at the knees!!) but whilst the cooling system is in bits replace

• thermostat (use Mazda one)
• if water pump is original then replace it
• temp sensor for ECU (aghh, my memory, think its the two wire one ... somebody will help me out)
• I skipped changing my radiator and guess what leaked 13 months later!!
• Radiator caps x 2

I also replaced all the hose clips (34 of 'em) but opinion is divided on how necessary that is. Certainly replace any that are corroded.

[Northern Bongolow]

yes its the 2 wire one. looks like a min list to keep things going for a while