The correct way to "Block Test" a bongo?

[Kolski]

Hey all.

My bongo 2.5TD has developed a bit of a cooling system gurgle which is resulting in sporadic overheating and I wanted to do a block test first to confirm if its exhaust gases (via the head?) or something else. The coolant system was checked over recently with a few old radiator pipes replaced early in year so, based on other bongonauts experience.. I'm thinking the head gasket is on it's way out. The bongo has just clocked 100,000 miles.

I've got hold of a testing kit with the fluid, test cylinder and egg-pump but the instructions are telling me to do this from the top of the radiator. This doesn't seem accessible without removing the air intake (for the turbo?). I've seen a few posts with test results.. green liquid etc .. and a few people mentioning doing it from the header tank although this result may not be as reliable as doing it from the radiator?

Can anyone help and provide or point me to a step-by-step to get an accurate result before I go off and buy a new head gasket kit?

Thanks in advance.

[missfixit70]

Header tank is the same coolant as the rad , do it from there, if you do it from the rad you'll empty out a litre or two of coolant from the header. FYI That air intake is just for the heater/aircon, should only be held on with two scrivets to expose the top of the rad.

[Kolski]

Thanks for the advice Kirsty.

Ok.. so I've set up the tester on the header tank. I let the engine come up to temp without the header pressure cap on and started the test with the engine still running.

What I noticed was that it seems to suck air in from the escape vent rather than through the cooling system. So.. I blocked the escape vent off and then the tester decided after a few pumps to just suck up a load of coolant and turned the liquid a blue/brown colour.

Right.. try again.. drain off some of the coolant from the header tank.. same thing.

The test says to pump gasses through for approx 1 min but all I'm doing it seems is either sucking in fresh air or dirty coolant.

[dandywarhol]

Where's the "escape vent"?

[Kolski]

The little black rubber hose just prior to the pressure cap on the coolant header tank.

But.. I think I've sussed it now.. I had to drain even more coolant out to give the test a chance to suck in air rather than fluid.

Thankfully, it didn't go yellow straight away but did take on a slightly greenish tinge after some vigorous pumping so diagnosis would suggest the start of a head gasket failure.

Costing up the replacement comes in at about £350ish for a new gasket, bolts, skim and labour.. Which is not too bad.

When I got the Bongo a few years ago with 80k miles on the clock I factored in about £1000 p/a maintenance costs and she's not been nearly as draining as I imagined. In fact, I think I'll give her a bit of a treat and spend a couple of hundred quid in the bodyshop and valet as well.

Cheers all.

[dandywarhol]

Still can't understand how its "sucking in air" from the overflow tube if the cap is off

[Aethelric]

How does the block tester work?
Does the block tester have to be in contact with the gas in the cooling system? On a "normal" engine this would end up in the top of the radiator or header tank, but in a bongo the gas collects in the head.
Or does gas dissolve in the coolant and is then given off in the head? And what gas is it looking for?

Dave

[missfixit70]

Looking for exhaust gasses in the coolant which should end up in the header/expansion tank.

[Aethelric]

Looking for exhaust gasses in the coolant which should end up in the header/expansion tank.

Any idea what exhaust gas in particular Kirsty? You don't get much carbon monoxide off a diesel, especially on low load. I think the main emissions are particulates. Is a block test actually reliable on a bongo?

[Nevets]

Looking for exhaust gasses in the coolant which should end up in the header/expansion tank.

Any idea what exhaust gas in particular Kirsty? You don't get much carbon monoxide off a diesel, especially on low load. I think the main emissions are particulates. Is a block test actually reliable on a bongo?

The blue liquid in the block testing unit changes to yellow/green when it detects carbon monoxide,with diesels engines it takes longer to test due to low amounts of carbon monoxide present in the vapour which is emitted out of the expansion tank when the engine gets up to temp..

The test is very reliable when used correctly
If the vehicle has suffered previous head/gasket problems and hasn't been flushed out it can still be detected.

Cheers Steve#

[Aethelric]

Looking for exhaust gasses in the coolant which should end up in the header/expansion tank.

Any idea what exhaust gas in particular Kirsty? You don't get much carbon monoxide off a diesel, especially on low load. I think the main emissions are particulates. Is a block test actually reliable on a bongo?

The blue liquid in the block testing unit changes to yellow/green when it detects carbon monoxide,with diesels engines it takes longer to test due to low amounts of carbon monoxide present in the vapour which is emitted out of the expansion tank when the engine gets up to temp..

The test is very reliable when used correctly
If the vehicle has suffered previous head/gasket problems and hasn't been flushed out it can still be detected.

Cheers Steve#

Thanks Steve. I was thinking of investing in a block tester. They seem to cost less than a garage charges for doing the test.

[dandywarhol]

The Sealey combustion leak tester detects CO2, carbon DIOXIDE.
You can also take it along to your friendly MOT station and ask them to use their 4 gas analyer to sniff for CO2

[Aethelric]

The Sealey combustion leak tester detects CO2, carbon DIOXIDE.
You can also take it along to your friendly MOT station and ask them to use their 4 gas analyer to sniff for CO2

CO2? Ah I can see how that would work.