my coolant is making me go bongo!

[LawrenceStanley]

Hi Guys,

I recently purchased a 1996 bongo, it's old but its a lovely vehicle. I've just completed a 2300km trip to and around Scotland from Cornwall and I have had some strange coolant issues I am hoping someone might be able to help with. fyi it has a low coolant alarm.

So firstly, the bongo looses coolant. I know that because on cold days after the engine hasn't run for a few hours the coolant level drops in the expansion tank and the alarm starts. This is the first thing i don't understand. Why not on a hot day during use?!

Anyway, due to being in remote places I have had to top up with regular water quite often. on one short (3mile) drive we parked up for a cuppa and i noticed loads of coolant dripping out of the bottom left corner of the radiator. checked all over and couldnt see a leak. Assumed it was from behind a fan but it definitely was not the coolant tank. topped up with water, drove around for at least 50 miles and no leak after...

On our 12 hour drive back to Cornwall, around Manchester, we encountered the inevitable traffic jam, after a while of stop starts i saw steam coming from the front bonnet! oh no, engine is cooked i thought, but luckily it was at that moment we started moving again. drove to next services (5 miles ish) and there was evidence of water spraying out, but no leak visible and topped up coolant tanks and all way good. by rights the engine should have been toast! but still cruising along happily...

Drove all the way back and the last 5 miles the temperature gauge started fluctuating, going from 11 o'clock to cold and back... and still no visible leak. radiator is still full. expansion tank not so much...

Does anyone know what on earth is going on?

[mikeonb4c]

Old Bongo radiators are known to start leaking where the top joins the matrix usually. Could it be that? Had to have mine replaced at about 20 years old.

P.s. don't much like the sound of the fluctuating gauge though. Need to find the cause. Hope there's no air got in the system esp as it can draw air in upon cooling when there's a leak that compromises the pressurised/closed system. Have a Bongo specialist look at it if possible.

[Bob]

Mike is right.

You have a leak which needs fixing, personally I wouldn't drive it until it's done as you will cook the head, if not done already.

Also, as Mike says, the system must be bled after working on it or if the level has dropped below the header tank. Search for 'Youtube Bongo Bleeding' or similar.

I'm guessing it's a diesel?

[g8dhe]

Sounds like it could be the coolant radiator - that is not the one you see from the front that's for the air-con, take the air scoop of and underneath you will find the coolant system radiator with the fans mounted on the back of it. The top section is plastic and the seal between it and the metal radiator below is a common place for leaks to appear. fairly cheap replacement cost £100 for the radiator itself.
Do remember the coolant system is a sealed and pressurised system, so don't open it when hot, an leaks mean your no longer reaching the correct pressure which can be disastrous.

[Northern Bongolow]

The bongo holds about 14lts of coolant.on a cold day this may actually measure 13.9. on a hot day it may measure more like 14.1. density and volume and ambient temps and all that tecky stuff.
The air space above the correct level in the exppansion tank is as important as the coolant level. The level must be set at the correct height or it will blow it out of the expansion tank, this then runs down behind the nearside headlight where you observed it .
Sat in a traffic jam after a long run may make the stat open, then the front fans come on to keep everything at the correct running temps, this could be when you see a little steam if there is water on the innards of the rad etc.
Your last sentance says rad full, exp tank not so full. This is correct and how it should be.
Q.
Are you filling the expansion tank to full.

[LawrenceStanley]

Thanks for your help guys! I figured out the coolant problem, there's a leak where the plastic radiator top clips in near the top hose. It was a slow leak but I still have no idea how i managed to drive from Scotland back home without cooking the engine!

I'm right down in the depths of cornwall so i think i'm going to have a go at fitting a new radiator my self, i understand it's a relatively straight forward job.... Does anyone know if its worth changing hoses etc while its all out?

Also this maybe a silly question, but where does one purchase 14l of coolant?

[g8dhe]

Well best to check the hoses and see what condition there in, but if they are original then they will most likely be close to or older than 20 years! I think I would be inclined to replace the large bore hoses which get the most flow and worst temperatures. The coolant comes as concentrate which you mix down to normally 50% - check the bottle - in which case you only need 7l of concentrate or possibly less.

[Bob]

Any car shop or Amazon can supply anti-freeze, also many super markets, eg Asda.

You mix 50/50 so need to buy a minimum of 7 ltrs. I'd likely buy 10.

It's important to use it all year as it contains a corrosion inhibitor to stop Bongy's inards rotting.

Also needs to be changed at 2 years, or 5 years if using 'long life', and it's important to flush out all the old coolant if changing the type.

[LawrenceStanley]

Good intel! I think i'll change all the bigger hoses as they are looking quite old. Is sticking a hose in there and flushing it through still a thing these days?

Out of interest, has anyone managed to successfully do the "see-saw" bleeding technique whilst also pressing the accelerator and checking the header tank all on their own

[Northern Bongolow]

Only if you have a walking stick handy and some good gloves

[Bonneville]

I'd do the steel large bore pipes as well:



Note the Norma clip on left and aircraft quick-release on right. Nothing would stop the weep from this crusty old pipe. Best replace them if the budget allows.

Sat in a traffic jam after a long run may make the stat open, then the front fans come on to keep everything at the correct running temps

Just a point of order, Mr Chairman, but does the stat cycle in this way on a Bongo? My 2.0 is the same as everything else I've worked on: stat speeds warm up of engine and is fully open after about 5-10mins (feel top hose for the stat opening point), once engine is at temp, stat remains open until engine shut down and cooled off. Idea is to reduce warm-up time not to participate once the head is at temp. Bongo may be different given size of cooling system.

[mikeonb4c]

A good point Bonneville and one i've had similar thoughts on despite insistance the Bongo has a very different / non standard cooling system. And surely stat opening and fans coming on are different events at different temperatures?

[Bonneville]

Yes, I agree. Rad fans will come on when the temperature exceeds a given limit. On an OBD2 vehicle that point can be read off the diagnostics but likely to be +100 and the stat will be wide open by then. Operating temperature of engine is above stat value (88), typically 90-95. Stat's job is to hold the water in the head so warm up time is reduced along with engine wear (and your feet get warm quicker in winter). Having the stat close while the engine is at temperature will reduce the circulation and I've not seen it yet but then I've not seen an installation like a Bongo yet...those coolant pipes are very long.

[ade33]

Pretty much the first job I did on our van was replace the radiator, after it sprung a big leak at the top. Replacement with a pattern rad was a straightforward task, and the bleeding process is long-winded but follow the YouTube videos precisely and you won’t go far wrong. I took it slowly with the bleeding for fear of making a hash of it, three of us spent most of an evening carefully see-sawing the air out the cold system before firing it up. Another 40 minutes or so saw it up to temperature and, fingers crossed, properly bled. No coolant problems since, though I do wish I’d replaced at least the big hoses while the system was open.

My top tip, make sure you get the right funnel to fit in the bleed hose securely. I lost count of how many bits and funnels I bought before finding the one that a) fitted neatly and b) didn’t leak or come adrift when it got hot. And it gets hot. Wear gloves and rig up some wire or something so you can hang the funnel up somewhere while you are bleeding.

[Bob]

And safety glasses.

Worth refering to 'Little Johny Head in a Bongo'.