Under bonnet seals - warning - do not remove

[glenhendry]

I made a silly mistake, and now I am paying for it... :redface:

Lesson: Do not remove any of the bonnet seals. I removed one of the two foam blocks at the rear corner of the bonnet where it contacts the firewall. I hoped that this would allow heat to escape when stopped, but I did not anticipate the drastic affect it would have on air flow while driving. It acted as a sort of chimney and hot air was channeled out the new hole instead of going under the car and caused the coolant reservoir to soften and then pop (under its 20psi pressure). Thankfully the missus pulled over and no major harm was done. The ABS reservoir also looked heat affected and a largish plastic duct that vents under the coolant overflow.

History: For a long while now I have been concerned about the under bonnet heat, especially relating to the fuse box getting baked for hours after the car is parked up, with the clam shell bonnet all sealed up like it is. Not only heat, but 'corrosive battery fumes' had also been mentioned in posts and I wanted a way to get the heat out once parked up. I considered a bonnet scoop but learned folks warned that they could have undesired consequences.

Question 1: can I use the ABS reservoir off an earlier model on my 2000MY HSE? I have one, and they look identical. I believe that it is off of a 1999MY.
Question 2: do you all see water flowing (visibly) into the coolant expansion tank from the smaller hose underneath the tank (towards the front)? I never noticed that before. It comes from the inlet manifold via the throttle body.

[glenhendry]

Also, be very very careful when handling the hard plastic tubes from the coolant expansion tank to the throttle body. After years of heat, they are brittle and break easily, I broke mine in 3 places handling the expansion tank. A new one is $55.

[mtb_gary]

I made a silly mistake, and now I am paying for it... :redface:

Lesson: Do not remove any of the bonnet seals. I removed one of the two foam blocks at the rear corner of the bonnet where it contacts the firewall. I hoped that this would allow heat to escape when stopped, but I did not anticipate the drastic affect it would have on air flow while driving. It acted as a sort of chimney and hot air was channeled out the new hole instead of going under the car and caused the coolant reservoir to soften and then pop (under its 20psi pressure). Thankfully the missus pulled over and no major harm was done. The ABS reservoir also looked heat affected and a largish plastic duct that vents under the coolant overflow.

History: For a long while now I have been concerned about the under bonnet heat, especially relating to the fuse box getting baked for hours after the car is parked up, with the clam shell bonnet all sealed up like it is. Not only heat, but 'corrosive battery fumes' had also been mentioned in posts and I wanted a way to get the heat out once parked up. I considered a bonnet scoop but learned folks warned that they could have undesired consequences.

Question: can I use the ABS reservoir off an earlier model on my 2000MY HSE? I have one, and they look identical. I believe that it is off of a 1999MY.

The ABS resevoir is just that, a resevoir. It is not under any pressure and as long as the level sensor plug is the same (I think it is) there should be no difference. Whilst you have the new unit off give it a thorough clean. When I did mine I let it soak in a degreasing solution for a few hours then flushed it thoroughly with water, then leaving it in the sun to dry out for a couple of days. It is amazing how clean you can get them ;).

Gary

[TheTree]

Mate

Sorry to hear about your dramas :(

The coolant overflow pipe is the same as the air hose, 6mm nylon. Or you could just run fuel hose the entire run.

55 bucks is ridiculous !

Steve

[Hoges]

Thanks for the heads-up! ;) Mine became detached and I simply glued them back with Loctite Superglue as a matter of course, not realising that their practical significance...:angel:

[PeterH]

To answer your question 2, yes, it is normal to see coolant entering the overflow tank in the location you describe.

[davidsonsm]

I made a silly mistake, and now I am paying for it... :redface:

Lesson: Do not remove any of the bonnet seals. I removed one of the two foam blocks at the rear corner of the bonnet where it contacts the firewall. I hoped that this would allow heat to escape when stopped, but I did not anticipate the drastic affect it would have on air flow while driving. It acted as a sort of chimney and hot air was channeled out the new hole instead of going under the car and caused the coolant reservoir to soften and then pop (under its 20psi pressure). Thankfully the missus pulled over and no major harm was done. The ABS reservoir also looked heat affected and a largish plastic duct that vents under the coolant overflow.

History: For a long while now I have been concerned about the under bonnet heat, especially relating to the fuse box getting baked for hours after the car is parked up, with the clam shell bonnet all sealed up like it is. Not only heat, but 'corrosive battery fumes' had also been mentioned in posts and I wanted a way to get the heat out once parked up. I considered a bonnet scoop but learned folks warned that they could have undesired consequences.

Question 1: can I use the ABS reservoir off an earlier model on my 2000MY HSE? I have one, and they look identical. I believe that it is off of a 1999MY.
Question 2: do you all see water flowing (visibly) into the coolant expansion tank from the smaller hose underneath the tank (towards the front)? I never noticed that before. It comes from the inlet manifold via the throttle body.

Can l ask what the concern or concensus is with bonnet scoops? I've been considering one as a way to reduce the under bonnet temp.

[TheTree]

Can l ask what the concern or concensus is with bonnet scoops? I've been considering one as a way to reduce the under bonnet temp.

HI

Given what was said in the other thread, I can't see that it is going to cause problems. As long as you take care while wading :eek:

Steve

[glenhendry]

Can l ask what the concern or concensus is with bonnet scoops? I've been considering one as a way to reduce the under bonnet temp.

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 (http://www.aulro.com/afvb/p38a-range-rover/147633-project-bonnet-scoop.html?highlight=scoop) thread.

[clubagreenie]

I did similar on a RRC, using a damaged plenum and cut out the vent section where it rises up in the centre and let's cabin air in. Mount it 2/3rd's back in the dropped centre part of the bonnet. Keep it facing forward and add side vents (use the vents from the D pillars (C if it's a 2 door)) to the rear corners if the bonnet sides (as per the pics in the bonnet scoop thread. Underneath about an inch below made a plate that ducted this air L&R down the sides and across the exhausts while the air flow from the front followed it's natural path through, down and out the underside rear.

Don't have pics sorry but hopefully you get the idea. It can face either way, as long as it's ducted to keep the air flows separated.

[glenhendry]

Question 1: can I use the ABS reservoir off an earlier model on my 2000MY HSE? I have one, and they look identical. I believe that it is off of a 1999MY.
Question 2: do you all see water flowing (visibly) into the coolant expansion tank from the smaller hose underneath the tank (towards the front)? I never noticed that before. It comes from the inlet manifold via the throttle body.

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.

[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.

[peter51]

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.

[Hoges]

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 (http://www.aulro.com/afvb/p38a-range-rover/147633-project-bonnet-scoop.html?highlight=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!

[DT-P38]

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.

[peter51]

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.

[Hoges]

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 ...:dbcry:

[peter51]

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

[Keithy P38]

Not with a snorkel :-)

[Hoges]

Not with a snorkel :-)

snorkels are cool!:wasntme:

[Keithy P38]

Haha that's a good one!

[benji]

Hoges, that was disgraceful. ..:p

Too many dad jokes for you.

[DT-P38]

Thermo over ride and snorkel would keep me happy for now... although i did see a nice scoop on HighRR's LS1 equipped P38 a few weeks ago. So where is that Lucky 8 snorkel kit at now? I'm sure I preordered one off the prototype posting a month or so ago!!!

P.S. Hoges I guess you think fridges and Air Cons are cool too? :-)

[glenhendry]

Do we have schematics from anyone on how to fire up those thermo fans from the fuse box or becm? I'd rather not chop into the wires up front.

Sent from my SM-N9005 using AULRO mobile app

[benji]

It should be able to be done from the hevac ecu. That way it'd run through the relays etc.

[peter51]

This circuit refers to the 1999 P38.
Simple - Remove your bumper. Then locate the condenser pressure switches on the LH side of the vehicle. One is 2 wire and the other is 4 wire. The 4 wire one faces for and aft and is closest to the centre of the vehicle.

The 4 wire one has one wire which is Black with blue stripe.
To get both fans to run in parallel at high speed all you need to do is to allow an alternative earth path for this wire. Use a scotch lock to tap in and then an inline switch in the cabin to switch to earth.
See attachment.

If you have a TM2 then you can use it to switch the fans via relay - Post if you want that circuit as well.

[glenhendry]

Great info, thanks. Dumb question, what is a TM2? Is it a timer? If so please do provide wiring diagram!

Thanks

Sent from my SM-N9005 using AULRO mobile app

[mtb_gary]

Glen

I'm guessing Peter51 is referring to the Engine Watchdog TM2 (and TM4).

ENGINE WATCHDOG TM2, Engine Temperature Sensor and Low Coolant Alarm (http://www.enginewatchdog.com/tm2.html)

Gary

[996TURBO]

I made a silly mistake, and now I am paying for it... :redface:

Lesson: Do not remove any of the bonnet seals. I removed one of the two foam blocks at the rear corner of the bonnet where it contacts the firewall. I hoped that this would allow heat to escape when stopped, but I did not anticipate the drastic affect it would have on air flow while driving. It acted as a sort of chimney and hot air was channeled out the new hole instead of going under the car and caused the coolant reservoir to soften and then pop (under its 20psi pressure). Thankfully the missus pulled over and no major harm was done. The ABS reservoir also looked heat affected and a largish plastic duct that vents under the coolant overflow.

History: For a long while now I have been concerned about the under bonnet heat, especially relating to the fuse box getting baked for hours after the car is parked up, with the clam shell bonnet all sealed up like it is. Not only heat, but 'corrosive battery fumes' had also been mentioned in posts and I wanted a way to get the heat out once parked up. I considered a bonnet scoop but learned folks warned that they could have undesired consequences.

Question 1: can I use the ABS reservoir off an earlier model on my 2000MY HSE? I have one, and they look identical. I believe that it is off of a 1999MY.
Question 2: do you all see water flowing (visibly) into the coolant expansion tank from the smaller hose underneath the tank (towards the front)? I never noticed that before. It comes from the inlet manifold via the throttle body.

I removed the side seals and under windscreen seal 3 years ago without any bad effect. Very strange is your story...

[glenhendry]

Very strange is your story...

I suspect that it is the combination of a missing heat shield on that side, climbing a mountain range in summer in the middle of the day while towing a heavy camper trailer.