Checking the Cooling system etc

[TonyBongo]

After sitting in my Garage for about 5 years, now that I’ve replaced the battery, replaced the old diesel and engine oil (ATF oil looks good), changed the fuel filter, and fitted a low coolant/engine temp alarm, I’m about ready to take my Bongo for an MOT to get it back on the road.

So far I’ve only ran it for short periods on the driveway, so I’m now ready to run it for longer to get the engine up to temp and check that everything, and in particular that the cooling system, is working properly.

Can anyone advise what I should check for, especially regarding the cooling system. I can observe the engine temp on the Haydn alarm and coolant levels in the header tank, look for water under the vehicle, and check that the front and rear heating systems blow hot, but is there anything else that I should check? E.g. how can I check whether the thermostat is working? When should the fans kick in?

Hopefully the engine will tick over happily at around 97C

Thanks

Tony

[wonkanoby]

you can feel bottom hose to radiator to see when stat opens

turning on a/c will get fans going

[haydn callow]

You seem to be doing all the right things.......just go ahead but if your low coolant alarm goes off, stop and find out why.
Your temp alarm should be reading about 85/90c if you have put the sensor on the back of the cylinder head as per instructions.

[TonyBongo]

Thanks Guys,

For the 'bottom hose to radiator', should I check this at the engine end (after thermostat), or at it enters the bottom of the radiator, or doesn't it matter? How hot should it get (barely, moderate or ouch). I imagine that it will only start warning up once the stat opens - any idea how long that is likely to take with engine idling or approx. how hot the engine would normally be before it opens (the engine temp sensor is on the back of the cylinder head as advised.

Cheers

Tony

[haydn callow]

It will take over 30 mins to open stationary, it may not open at all when driving normally. A hot day going uphill may well get it open.
When it does open the bottom hose where it exits the rad will be to hot to hold for more than a few seconds.

[TonyBongo]

Thanks again - I'll let you know how I get on.

[mikeonb4c]

Personally, i look for the standard temp gauge to be moving off the cold stop towards its 11 o'clock position about 5 mins roughly after engine start and moving off on my diesel Bongo. It used to take 10 mins before a new thermostat was fitted. I'm not saying that's a perfect check, but its a healthy indicator. I've had similar experiences on other cars also.

[haydn callow]

Mike,
I doubt a thermostat would be anything but closed under those circumstances. The temp sensor is on the head/block so unless your gauge is modified the stat opening/closing would not affect the gauge.......I drove all the way from Somerset to the bash and the stat never opened......I then checked about a dozen others arriving from all over the country, not one had a hot bottom hose, just slightly warm.

[mikeonb4c]

Mike,
I doubt a thermostat would be anything but closed under those circumstances. The temp sensor is on the head/block so unless your gauge is modified the stat opening/closing would not affect the gauge.......I drove all the way from Somerset to the bash and the stat never opened......I then checked about a dozen others arriving from all over the country, not one had a hot bottom hose, just slightly warm.

I know nothing about the science i'm afraid, just what i observed. But could we be missing something here. The behaviour of the gauge and the behaviour of the thermostat require different discussions. Regarding tbe gauge, it clearly knows the different between a cold engine and one that has reached operating temperature. And the time the needle takes moving from one positiom to the other feels like the time an engine might take reaching its operating band. Turning to the thermostat: if, for example, a thermostat was not responding properly could it perhaps be allowing coolant to circulate in a cold engine when it shouldn't be allowing it. And if so, might an engine take longer to reach operating temperature? And might it be safer/sensible if by design old thermostats failed in the open position? I don't know but maybe someone could comment?

My wife had a Nissan Sunny, similar vintage as the Bongo. Its engine temp gauge needle was slow to move off the stop and reach the mid position from a cold engine start. The heater was also not very effective. This was most noticeable when on the move in cold weather. I suggested she ask the mechanic at the garage whether it might need a new thermostat. The mechanic dismissed that idea, 2 years running at service time. The third year i took it in for her and said i wanted it changed regardless. The problems ended immediately.

Which is why i offer my observations, without prejudice

[Northern Bongolow]

you are quite correct mike in what you say, and it indeed could be applied to a bongo.

as an add on to that, the bongo temp gauge doesnt move until the engine/head coolant temp is very near 50 deg c. this is backed up with other gauges i have fitted. this doesnt mean that the entire system is at 50 deg, just the heater loops and the top rad recirc loop that goes through the expansion tank back to the engine. the expansion tank is a good easy place to measure system temps if you want to point one of those infa red guns at somewhere.

the bottom hose circuit will be a lot lower in temps until the stat starts to open, this is 82 deg c.

to do a rubbish test on the stat (in place ) squeeze hard the bottom hose with the engine not running, this will lift the jiggle pin (float) on the stat, this will make it click or tic. this may mean that the stat is closed, it also says its got a stat in the system . if the stat is stuc open it probably wont tic as the water will take the easy route through the stat and the float is already lifted or floating.

[mikeonb4c]

you are quite correct mike in what you say, and it indeed could be applied to a bongo.

as an add on to that, the bongo temp gauge doesnt move until the engine/head coolant temp is very near 50 deg c. this is backed up with other gauges i have fitted. this doesnt mean that the entire system is at 50 deg, just the heater loops and the top rad recirc loop that goes through the expansion tank back to the engine. the expansion tank is a good easy place to measure system temps if you want to point one of those infa red guns at somewhere.

the bottom hose circuit will be a lot lower in temps until the stat starts to open, this is 82 deg c.

to do a rubbish test on the stat (in place ) squeeze hard the bottom hose with the engine not running, this will lift the jiggle pin (float) on the stat, this will make it click or tic. this may mean that the stat is closed, it also says its got a stat in the system . if the stat is stuc open it probably wont tic as the water will take the easy route through the stat and the float is already lifted or floating.

Thanks Ady, reassuring to hear that. I know the Bongo system is a complex one, with the heater circuit playing a part in it, so direct comparisons with a Nissan Sunny aren't possible. But the change in behaviour in the Bongo gauge before and after fitting a new stat was quite marked - you couldn't miss it really. And I had a tremendous feeling of deja vue when it happened

[TonyBongo]

Test went OK I think.

Ran engine, primarily on idle. It took about an hour to get up to 97c (according to Haydn cylinder head temp gague) at which point fans would intermittently kick in bringing temp down to 91-94c. Bongo temp gague moved to 11 o'clock position when the engine reached around 70c.

Vents blew warm air front and back when switched on.

Hose at bottom of radiator was initially cold then got warm/hot after engine had ran for a while.

No sign of any liquid escaping. Coolant appeared to rise about 5mm in header tank and the hoses at the bottom of the header tank and the tank itself felt warm.

Nice to have the Haydn temp gague-gives confidence to do the test (and drive the van).

[TonyBongo]

Is getting up to 97c sat on idle on driveway ok? Would the temp be lower if vehicle was moving and has airflow over engine, even if revs are higher? I won't know until I drive vehicle to garage for service and MOT.

[mikeonb4c]

Is getting up to 97c sat on idle on driveway ok? Would the temp be lower if vehicle was moving and has airflow over engine, even if revs are higher? I won't know until I drive vehicle to garage for service and MOT.

Yes I think it should. I've yet to mount my TM2 sensor in the approved position but to give you an idea my TM2 shows 85c or thereabouts in traffic, dropping to 72c or thereabouts when on the move (and engine not doing exceptional work) and/or when I switch the scavenger fan on. My sensor is a bit more exposed to airflow than the approved position so the movements are probably more exaggerated, but they illustrate the significant cooling effect of airflow.

[Simon Jones]

Have you changed the coolant and brake fluid? Both have a 2 year replacement schedule regardless of use. Maybe once you've had the maiden voyage it would be worth changing both. The anti-corrosion properties of the coolant will be be quite weak by now and the brake fluid absorbs moisture over time which can cause rusting within the brake calipers as well as a spongy brake pedal.

The temperature will be lower once the vehicle starts moving as the air flows thru the radiator. On my V6 at motorway speeds, the coolant leaving the radiator can be up to 30C lower than going in.