Thread: Under bonnet seals - warning - do not remove

Originally Posted by glenhendry

Question 3: does anyone know what the ~10mm hard plastic tube is that terminates between the firewall and the coolany reservoir? It looks like a vent, and travels downwards towards the axels. It is much bigger and less flexible than the diff breathers tubes.

This melted tube is the breather tube from the carbon cannister. On late models the canister is down near the EAS tank, on earlier models it is over behind the EAS where the THOR Engine ECU is.

Hi Glen,
The cooling system is designed with great attention to detail by the cooling engineers so that the hot air is channelled down below the engine. They put pressure transducers around the bottom and front inlets and throughout the engine bay – then they measure the static pressures at many locations on both inlet areas and exit areas – at all engine loads including stopped idle.
They then modify seals and baffling to achieve the desired flow directions. This is modified by the swirl created by the engine fan – so there is quite a bit of design involved.
I’m not an engineer but I have just come from the state library where I was researching the topic.
So don’t remove any baffling whatsoever and make sure that all the seals and baffling along the edges of the radiator and AC condensers are in place.
The bonnet scoop would have to be designed in regards to the science involved, and anyway I think it would really detract from the beautiful lines of this vehicle.
For me this vehicle has the most beautiful design lines of any 4WD ever built.
You can setup a switch inside the cabin to switch your condenser fans on when stopped in traffic. I can send you the circuit if you like. This is my setup.
The heat dissipation to the atmosphere at idle ( stationary)on a hot humid day is very close to that of towing a heavy load or climbing a steep hill at about 80km/hr. The cooling system and particularly the radiator must be in tip top condition. Your coolant must be 50 -50 mix to depress the boiling point and stop any vapour forming in the coolant as it leaves the radiator enroute to the pump inlet – see my post on 300TDi overheating.
If you buy the TM2 engine watchdog – it has an auto switch facility that you can setup with a relay to switch them on at a set head temperature. This is my next job, having recently fitted the TM2.
The themistor for my TM2 is attached behind the alternator bracket – closest to the water jacket leaving number 2 cylinder( front right). The highest I have ever seen is 102 Celsius. Allowing for a plus or minus 2 degree error, this is still OK. An air cooled aircraft engine has a maximum oil temp redline of 135 Celsius.
BTW the hottest part of the coolant is where it rises at the back of the block. I have a separate coolant temp sensor there. It reads within 2 degrees of the TM2. As i said my TM2 is sandwiched between the right side head and the alternator bracket.
I also have a low coolant alarm by READRC tapped into the manifold just beside the standard temperature thermistor. This will stop my wife from driving if coolant is lost, as the alarm is very loud and she hates it as it tests its alarm as an integrity check on startup – if it stays on during start then she knows to stop and check water and she could not stand to drive any further if it goes off along the road somewhere – gotta love that‼
My radiator is the original at 13 years old( has been rodded 2 years ago) – but I never see water temps in excess of 102 Celsius idling is heavy traffic on hot humid SE Queensland days. When I switch on the condenser fans it drops it only by 3 degrees.
Hope this info helps.

Originally Posted by glenhendry

The problem is that the bonnet scoop will cause an area under the bonnet with higher or lower pressures, and this may stop or hinder through the radiator.

I think the best option to cool under bonnet once stopped is to fire up the air con condenser fans (off the aux battery) for a few minutes on a timer.

Here is the bonnet scoop thread.

Using the electric fans to dissipate heat sink effects works very well. I had a V6 Calibra for several years where this was standard fit. In that instance it was activated by a thermostat rather than a timer. In colder weather (15-20 degC ambient) it might run for 2-3 minutes depending on how warm the motor was. In hot weather (30 degC+) it would run for up to 10 mins.

After a long run home in Qld summer I usually raise the bonnet for a couple of hours!

Originally Posted by Hoges

After a long run home in Qld summer I usually raise the bonnet for a couple of hours!

Started doing this on hot days last year...

Mental note: Must fit that over ride switch for thermos before summer sets in.

To help this thread along I compared water temps at idle with the bonnet up and with the bonnet closed.
There is really no difference - maybe 1-2 degrees.
I left the car idling bonnet closed in the midday sun today for 10 minutes after a highway drive following by driving in traffic. The temp was 92 degrees.
I then lifted the bonnet and left it idling for 10 minutes - there was a light breeze blowing - the temperature stabilised at 91.
So the ultimate bonnet scoop to release heat during iding stopped in traffic would be no bonnet at all - however it makes no difference.

while I take your point regarding water temperatures, it's not just the water temp but rather the build up of the ambient still air temp under the bonnet after the engine stops and the exhaust manifold, radiator, engine block etc all radiating heat into the relatively small space just under the bonnet... where the EAS, battery and engine ECU reside. While it might get warm there during a hot run, at least the air is moving...I've yet to plot the rise in heat sink air temp. could be an interesting exercise!

PS I agree with you about the design lines.. I suspect that's what attracts most of us! I feel the same way about the YE Calibra. I had the 2.5L 5 sp manual V6 model which was a completely different beast from the dreaded 4 cyl version. Totally reliable, a CD of 0.25 or thereabouts ... was a sad day when the lease was up ...

Yes everything gets pretty hot for sure - but no different to any modern 6 or 8 cylinder. It is certainly an issue to think about. The ECU in the Thor P38 draws cooling air from the cabin - so that should be ok. Battery gets very hot.

Inlet air temps are also very elevated - 50 Celcius on a 30 degree day. You can watch it rise at idle stopped at the lights - monitor with any OBD tool

Not with a snorkel :-)