Over heating enquiry

[jsforest1991]

Hi Everyone,

I'm after some troubleshooting tips.

I have had my Bongo since October 2020, I managed to do about 2000 Kms in it and it appeared to be working fine.

About three weeks ago I took it out for the day. I was fixing my roofbox so had it ticking over for a while (30 mins) then took it for a two mile trip. On restarting the coolant alarm came on. I checked and topped up with 1/2 litre.

I then took it on another 2 mile trip and sat having some lunch while it was ticking over. I then heard the cooling fans come on, temp gauge hadn't moved and saw water, popped the bonnet and water was coming out of the tank overflow pipe. I turned the engine off and left it for 30 minutes. I checked the coolant, put another 1 litre in to get it to the marker in the tank and set off again to get it back home.

100 metres later the temp gauge went straight to hot and I pulled over.

My friend then told me about the see saw trick to get air out of the system, so we tried that and I managed to very slowly get the van home with the temp gauge going to 1pm ish. While doing the see saw test we noticed by taking the plastic cover off the radiator cap was not fitting correctly and losing water very slowly.

After this I installed the Rusty Bongo bleed kit as I had one, just not managed to fit it yet and did a full drain and bleed of the system and put new coolant in. Put a new 1.1 pressure rad cap on and when turning the engine on, the coolant level raised and started to overflow. My heart sank as this is a sign of a HG failure. My friend contacted Rusty and they suggested a stuck thermostat could also cause this.

In the meantime I noticed my front fan was no longer blowing.

So the following week, I changed the thermostat after draining at the radiator the drain plug and whatever came out of the housing. I fitted the new thermostat, put the coolant through a muslin cloth as plenty of bits had come out, filled, bleed the system the best I could for air. This time getting about 6 litres out and putting about 7 litres back in. I started the engine and the coolant did raise, followed quickly by bubbles and dropped, it kept doing this for a while but never overflowed from the tank. Great, I thought, I might be lucky and its air and not the HG. I then did the resistor modification to the temp gauge to get a better reading from it. I then did a stationary warm up and the thermostat opened as the radiator bottom hose got warm. I then tested the old thermostat in a pan by boiling and it did open!! OK, I must have had a real large airlock

I took it for a short drive of two miles 30 mph, never going over 2rpm and everything appeared to be OK. Took it for a 6 mile run on 50mph, the gauge went to midday after mile 3'ish stayed for another mile then started going up until it reached one and never dropped. I checked the bottom hose from the rad it was warm and no fans on.

As I still had a problem, I had a water pump to change as part of servicing to do so I put this on. Had new alternator belts and I put those on and I also changed the radiator. I drained and bleed again, this time getting 10 litres back in. I did the stationary test again and the bottom pipe opened. I then took it for a two mile trip,, the temp guage got to 12:20'ish, got back home, kept it at 2000rpm while stationary and the temp dropped to just below midday. Great, the thermostat must have opened to the radiator and its cooled. My front interior fan was still not working (as expected) but tried the rear fan and working and blowing hot air.

I then took it for a 4 mile trip and the temp guage got past midday and kept going, I parked up the cooling fans were on and the bottom hose cold. When I turned off, after 30 seconds, I could hear bubbles going to the coolant tank. I left it for 1.5 hours, did the return journey the temp gauge was a little lower, parked up, cooling fans were on and bottom hose not warm. I then left a few hours and checked the coolant and I have not lost any or any major amount. My friend suggested keeping a little stick to use as a marker so I have some idea if its lost any. So I did that, therefore I can say I did not appear to loose any.

My next plan is to get a compression test to understand if my HG has failed and I'm going to keep squeezing pipes. I still think i have air in the system. I will also do a pressure test on the cooling system with the old tyre valve.

If anyone has any experience similar to mine or tips on what to try, it would be much appreciated.

Another point, I've been smelling the coolant tank when bubbles come up with the top off and I can only smell coolant and not gas. But that could be completely down to my smelling ability.

Thanks

[Ian]

Here's something else you could try. It's test to see if your cylinder head is buggered. It's taken from the "Overheating" fact sheet in the members area of the main BF website.

The best way to prove the theory is by taking the vehicle on a 30-minute run and parking it up for the night. When the engine has cooled enough to work on, remove the glowplug rail and all four glowplugs from the cylinders. In the morning, return to the vehicle and place a strip of card some 9” by 20” (20 x 40cm) across the top of the glowplug holes and turn the engine over. the glowplug holes act as vents and anything in the cylinder will be forced up through them rather than down the valves. With any luck you will have three black carbon styles ‘splots’ and a larger watery splot where water has collected in the cylinder overnight. (Note, it is possible to have failure in more than one cylinder.)

[jsforest1991]

Great, thanks. I will test that

[g8dhe]

You are aware that there is also the scavenger fan that is used to keep the engine housing cool when there isn't any air flow from moving ? Given that you can't actually see any of the fans with out opening the passenger seat (scavenger fan) or removing the cabin air intake under the bonnet to see the radiator cooling fans the various fan noises can be confused.

[jsforest1991]

Hi Geoff,

Thanks for that.

Both times I referenced the front fans, I was stood at the front of the Bongo and the engine running and the fans were loud. Do you think this could still be the scavenger fan?

Also if it was that and not the cooling fans, do you think something is wrong with my temp sensor?

So I should check this on the next test, thanks for that to confirm which set of fans.

Cheers

[Ian]

This is from the Bongo Clinic:

Q: Can you explain what the different fans are for? I understand that there are radiator fans, and a scavenger fan? What do they do? (Barry from Monmouth)

A: The Scavenger fan is the one situated directly in front of the engine pointing upwards, it pushes air through the engine bay. It mainly comes on when static and the normal airflow has stopped hence causing the engine bay itself to heat up. It is controlled by an air-input sensor. The engine cooling fans are the ones behind the radiator which draw air in to cool the radiators, they also come on when the air con is selected to ensure that the air con radiator receives sufficient cooling. They are controlled by a temperature sender unit that sits low down on the cylinder head.

[jsforest1991]

OK, I've managed to borrow a compression testing kit, I'll do that and post the readings.

I'm also tempted to get a digital temp reader to get a better idea of the engine temperature instead of just the 'mod' temp gauge.

[Ian]

If you are going to get a proper tem gauge, these are the best: http://www.coolantalarm.co.uk/shop/inde ... oductId=26

[rita]

OK, I've managed to borrow a compression testing kit, I'll do that and post the readings.

I'm also tempted to get a digital temp reader to get a better idea of the engine temperature instead of just the 'mod' temp gauge.

Could I ask, what is the compression kit, and how to use it ?

[philsteward]

OK, I've managed to borrow a compression testing kit, I'll do that and post the readings.

I'm also tempted to get a digital temp reader to get a better idea of the engine temperature instead of just the 'mod' temp gauge.

Could I ask, what is the compression kit, and how to use it ?

Hi, it is my diesel compression testing kit which I have lent to the OP, removal of either the glow plug or the diesel injector, use the correct adapter, turn the engine over and record the compression reading. Complete on remaining 3 cylinders in the same way, and the readings should be within 10% at most of each other.

Something similar to this...https://www.ebay.co.uk/itm/262967984849

[willow2u]

I did a mod on my previous bongo bought a digital temp gauge and sensor got an ally t piece which screwed into head so I could use new sender and original. Took dash gauges out and cut digi gauge into a gap on the right hand side of temp gauge so it was nicely in eye line perfect and had modded original gauge as back up sorted

[jsforest1991]

Sounds very neat.
Got any pictures and details of the make of sensor?

Cheers

[willow2u]

I’ll dig through old hardrive see if I can find them worked really well to

[willow2u]

Also while I had the cluster apart I bought a float switch cut hole in expansion tank put float switch in there and plumbed wiring into back of cluster into an unused symbol on left or right side so if level dipped it would light up. It never did dip but I would randomly test it by poking it down a bit to make it light up just peace of mind

[rita]

OK, I've managed to borrow a compression testing kit, I'll do that and post the readings.

I'm also tempted to get a digital temp reader to get a better idea of the engine temperature instead of just the 'mod' temp gauge.

Could I ask, what is the compression kit, and how to use it ?

Hi, it is my diesel compression testing kit which I have lent to the OP, removal of either the glow plug or the diesel injector, use the correct adapter, turn the engine over and record the compression reading. Complete on remaining 3 cylinders in the same way, and the readings should be within 10% at most of each other.

Something similar to this...https://www.ebay.co.uk/itm/262967984849

Hi than for your reply , I thought it was some sort of new coolant test kit. Its worth a try but I doubt if a cylinder compression test would show up, especially as these heads usually have a hairline crack in the valve chamber. Never the less I suppose its worth a try. Good luck.