Pressure V Temperature

[Aethelric]

Driving south on the M6 this afternoon steady 70 my pressure gauge was reading 15psi (my thermostat is where it should be on the outlet of the head) now and again the pressure dropped then recovered. Now I also record water temperature (metal temp wont record this) , so what was happening?

The thermostat was working (opening and closing)

So are you looking for help, or comments, or questions or.....

[daveblueozzie]

I'm not mechanically minded. i don't understand half or even most of the techie stuff. Mazda/Ford built the bongo, it works for most of us, but your not telling me they didn't develop as they went along, if they built a bongo today do you think it would be exactly the same in every way under the bonnet/seat in the engine compartment..
TGP has developed a different system that he is testing and trying to let everyone know that it works. don't belittle a person for changing something that works, that is what the Japanese have done to everything that has been developed, they make it smaller/better more user friendly. thegreatpretender has only done what the Japs have been doing for years, hes trying to improve the cooling system to work better. i don't know if it's good or bad ,if it works great, if it doesnt its back to the drawing board. but please don't snub an idea that may just have been developed if someone had brought it forward in the first place.

SORRY rant over.

[dandywarhol]

Driving south on the M6 this afternoon steady 70 my pressure gauge was reading 15psi (my thermostat is where it should be on the outlet of the head) now and again the pressure dropped then recovered. Now I also record water temperature (metal temp wont record this) , so what was happening?

The thermostat was working (opening and closing)

Maybe the top tank pressure relief valve opened now and again - it shouldn't of course, unless someone's been messing about with the design of the system and it is overpressurising......................

[roosteruk]

I'm not mechanically minded. i don't understand half or even most of the techie stuff. Mazda/Ford built the bongo, it works for most of us, but your not telling me they didn't develop as they went along, if they built a bongo today do you think it would be exactly the same in every way under the bonnet/seat in the engine compartment..
TGP has developed a different system that he is testing and trying to let everyone know that it works. don't belittle a person for changing something that works, that is what the Japanese have done to everything that has been developed, they make it smaller/better more user friendly. thegreatpretender has only done what the Japs have been doing for years, hes trying to improve the cooling system to work better. i don't know if it's good or bad ,if it works great, if it doesnt its back to the drawing board. but please don't snub an idea that may just have been developed if someone had brought it forward in the first place.

SORRY rant over.

Its not belittling him Dave.
I understand what TGP is saying, I am a Time Served Diesel Fitter. I have worked on engines all my life and I know what TGP is right. I have not come across a system where the thermostat holds back cooler coolant, but the Japs had many millions of £££' more than TGP to develop the system thats fitted. I am not saying I distrust his findings or ideas, I just don't think it should be fixed as it isn't broke, unless he has lots of £££'s to investigate his idea. Remember, lots of engines are blown to bits on test-beds, before the answers are found by manufacturers.

The systems I have worked on, have the thermostat fitted so that it holds back coolant that is getting hotter as the engine runs. As the temp reaches an optimum level, the thermostat opens, allowing the hot coolant into the radiator, thus cooling it.
According to what TGP initially said, the thermostat on a Bongo works in the opposite way, in that it allows cooled coolant into the engine. This seems wrong as the cooled coolant from the radiator, is likely to close the thermostat. Now if I have that wrong, I am sure TGP will put me right, if its correct, then I hope he tells me so too?

Karl

[Aethelric]

Oh I see. Its a one of "those" questions.

Your thermostat opened allowing hot coolant into the top hose and the header tank. This heated up the air in the header tank causing an increase in pressure in the cooling system as whole. When you eased of the throttle the header cooled and the pressure reduced.

[The Great Pretender]

Thanks Dave, im not puting anyone down just trying to move the coolant/ head problem forward. The reason for this thread was because I was supprised that the Bongo ran so cool in those conditions. Im not prepaired to shoot anyone down on here but would love the chance to talk face to face with some.
As other threads have been locked because of attitude please close this one down.
I am not posting anymore threads on this site as it upsets some.

Dandy im not gonna reply, you belive what you want.
Rooster the stat requires the coolant entering the engine above 82c to open it...........how hot do you think it will leave the engine?

But I will be back.........................

[daveblueozzie]

TGP has requested this thread be locked , i will lock it if needed or delete any post as needed. please keep this section of the forum for techie stuff not for sarcastic remarks or bad mouthing people.
TGP has given a lot of info on the forum some of you may have benefited from it. we hope he will keep posting his findings .

[dandywarhol]

The stat will open at 82 deg. by whatever method of temperature it can get. That could be by coolant temp, engine/stat housing heat soak temp. or a combination of both.
Either way, it starts to open at 82 and is fully open at 95. The temp of the coolant LEAVING the engine in a conventional Bongo setup is controlled by the design of the system which includes the heat conduction from the cylinders, volume of coolant, the surface area of the pipes/radiators/tanks etc.

The majority of modern vehicles have a wax stat which starts to open between 88 and 92 deg. and are prone to fail more often than one operating at a lower temperature.
It's my belief that Mazda (and VW/Audi since the early 80s) have elected to go down the "stat in the return side" to make the system more reliable - as long as it's regularly serviced.

Some manufacturers are now fitting microprocessor servo controlled thermostats to enable the cooling system to operate within closer tolerances than before - and to overcome the unreliability of a waxstat operating under duress.

(This opinion is not designed to cause controversy and shall not be used in a court of law )

[haydn callow]

The header/expansion tank is part of the bypass/heater circuit, It always has "hot" coolant flowing through it, it is not dependant on the stat being open.

[Aethelric]

The header/expansion tank is part of the bypass/heater circuit, It always has "hot" coolant flowing through it, it is not dependant on the stat being open.

Us normal folk have hot water in the header all the time, but TGPs has got the stat in the top hose so the header will only get flow when its open.

Dave

[haydn callow]

Won't that mean the heater will be warm/hot/warm/hot ?? this is all to much for me to absorb.

[lizard]

I have spoken to Haydn at the Woodlands meet, but I dont think I explained my problems very well. So here they are.

As a simple owner who has no expert knowledge of the bongo system and having read loads of the posts on overheating I am still confused. Should the bongo show some, all or none of the following:

1 After a long high speed run have a bottom hose that feels as hot, (extreamly can't hold it for long) as the top hose. All the other hoses are hot as well as the header/degassing/expansion tank.

2 None of the fans are running, rad or scavanger.

3 Leaving the engine ticking over, the temp gauge climbs towards hot, I then chicken out and switch off.

4 When in traffic, the gauge slowly climbs towards the hot mark, if the hot mark is 2:00, then the needle is at 1:30, at this point I switch off no matter where I am.

5 If the traffic moves away at a reasonable rate cooling increases and the gauge goes back down to around 12:00/12:30

There is no coolant loss, Haydn alarm fitted, Mason alarm fitted, it has had a new head last year (previous owner), hoses changed, new water pump and a full service in Feb this year.

I am not sure if it is on its way to over heating or not. Everything appears to be hotter than any vehicle I have owned, inside and under the bonnet. Any thoughts on this subject would be of great help and stop a great deal of worring and confusion.

I put it on this post quickly before it gets locked

[Aethelric]

Hi Lizard

It sounds to me like your rad fans aren't operating. They are crucial when the engine is hot and the van stationary or slow moving. It could be the ECU sensor or defective fans (I found one on my bongo) or relays.

Dave

[lizard]

Thanks, that will give me something to look for and check

[The Great Pretender]

Thanks, that will give me something to look for and check

Just open the bonnet and turn on the air con to see if they work, they should be on.
Never had mine come on to cool the system.