Cooling- it's hardly rocket science, is it?
Discussion
Right- I have had my Cerbera since June now, and it has behaved itself pretty well, except it overheated the other weekend going to the Griff Growl and now I am paranoid about it. It is possible that a freak occurance prevented the fan coming in on an isolated occasion, as I sat in traffic for a while on the way to the Monster Meet and the temp sat at about 110 degrees (The dial over reads by 5 to 10 degrees compared to a laptop reading)but I did have the heating on full blast to help things a bit, which was not much fun on a hot day. To ease my nervous twitch when sitting in traffic I am thinking of making some improvements.
Firstly, as a 97 car it has only one fan, not 2 as others I have seen, and on the Griff it replaced. So firstly I am thinking: upgrade to 2 fans.
Secondly, having checked it all out after the incident, fan coming on as it should at about 92 degrees (on laptop) but I think that is a very high temp to come in at, only 8 degrees off boiling. Is there a way of making it come in earlier? For example, on my Saab 9-5 the fan seems to come in much earlier and run for longer, including after the ignition is switched off (The cerb actually only boiled over when I stopped and turned the engine off, I guess because the coolant was no longer circulating in the rad. Result: only Cerbera at the GG on the Saturday, and I was sitting in a puddle of coolant; not good for the image!)
Thirdly, I would ike to add a fan over ride so I can manually switch it in early, if for example I stop in traffic. As this car has no air-con fitted I have a plan: There is a switch for aircon on the dash, and a cable at the front of the engine labeled "aircon clutch" I have not tested it yet, but I hope that the switch, when on, will result in some voltage at the end of the wire, allowing me to use it as an over ride somehow. Has anyone tried this, or done it in a different way?
It can't be that difficult to improve the situation, I hope, as there are plenty of big V8 engined cars out there these days from the main stream boys, and they seem to manage to control their temperature quite happily.
Thanks in advance
Jon H
Firstly, as a 97 car it has only one fan, not 2 as others I have seen, and on the Griff it replaced. So firstly I am thinking: upgrade to 2 fans.
Secondly, having checked it all out after the incident, fan coming on as it should at about 92 degrees (on laptop) but I think that is a very high temp to come in at, only 8 degrees off boiling. Is there a way of making it come in earlier? For example, on my Saab 9-5 the fan seems to come in much earlier and run for longer, including after the ignition is switched off (The cerb actually only boiled over when I stopped and turned the engine off, I guess because the coolant was no longer circulating in the rad. Result: only Cerbera at the GG on the Saturday, and I was sitting in a puddle of coolant; not good for the image!)
Thirdly, I would ike to add a fan over ride so I can manually switch it in early, if for example I stop in traffic. As this car has no air-con fitted I have a plan: There is a switch for aircon on the dash, and a cable at the front of the engine labeled "aircon clutch" I have not tested it yet, but I hope that the switch, when on, will result in some voltage at the end of the wire, allowing me to use it as an over ride somehow. Has anyone tried this, or done it in a different way?
It can't be that difficult to improve the situation, I hope, as there are plenty of big V8 engined cars out there these days from the main stream boys, and they seem to manage to control their temperature quite happily.
Thanks in advance
Jon H
I've also got a '97 car, but with Aircon. I've rewired both fans using a direct feed from the battery and some relays. I've also changed it so that both fans come on at the lower temperature trigger. Normally the ECU switches on the first fan at 92 degrees and the second at 95 (or something like that).
It would be easy to add a manual overide in this case.
This never made sense to me, as if the car is hot, its hot.
These seem to have made a worthwhile difference (along with the bonnet mounted numberplate
)
>> Edited by simonsparrow on Thursday 8th September 14:19
It would be easy to add a manual overide in this case.
This never made sense to me, as if the car is hot, its hot.
These seem to have made a worthwhile difference (along with the bonnet mounted numberplate
) >> Edited by simonsparrow on Thursday 8th September 14:19
Two fans are the aircon cars.
If you want to ease your twitchyness. Take off the engine cover at the front and you will see all the pipework. If you find the very thin metal pipe with a spirally thingy round out, coming from one of the pipes just behind the rad, and follow it. I will almost guarantee that it is tie wrapped to the water pipe under the airbox or very close to the manifolds. It then goes in the wing near the master cylinder area to the dashboard.
Reroute this pipe and attach it to the chassis rail instead of the water pipe. Your gauge temperature will start reading much closer to ECU temp. It gets rid of the clenched buttocks moments as you sit in traffic.
Sorry for the technical words used such as thingy but if you look you will see what I'm talking about.
If you want to ease your twitchyness. Take off the engine cover at the front and you will see all the pipework. If you find the very thin metal pipe with a spirally thingy round out, coming from one of the pipes just behind the rad, and follow it. I will almost guarantee that it is tie wrapped to the water pipe under the airbox or very close to the manifolds. It then goes in the wing near the master cylinder area to the dashboard.
Reroute this pipe and attach it to the chassis rail instead of the water pipe. Your gauge temperature will start reading much closer to ECU temp. It gets rid of the clenched buttocks moments as you sit in traffic.
Sorry for the technical words used such as thingy but if you look you will see what I'm talking about.
I bought a new alloy rad from Radtec with two fans and the cowling already mounted for my 97 4.2 without aircon, reasonably priced too.
Never had a problem since, the system doesn't even need topping up from month to month and I use the car all the time, 12,000 miles a year, some in London and sprint it in the Challenge Series. Fans come on at 92 and 95.
You will need to put another relay in the panel in the boot, just plug it in the wiring is already there, you will also find another connection in the engine bay for the second fan.
Whole job took about 90 minutes.
The single fan and old rad are basically not up to the job.
Never had a problem since, the system doesn't even need topping up from month to month and I use the car all the time, 12,000 miles a year, some in London and sprint it in the Challenge Series. Fans come on at 92 and 95.
You will need to put another relay in the panel in the boot, just plug it in the wiring is already there, you will also find another connection in the engine bay for the second fan.
Whole job took about 90 minutes.
The single fan and old rad are basically not up to the job.
jon h said:
It is possible that a freak occurance prevented the fan coming in on an isolated occasion,
Might have been a dirty plug/ bad connection to the fan sender, if you unplug the sender plug the fans should run on default mode continuously, but unfortunately it is located under the lower cover.
Caveat pre-emptor: I am not a mechanical engineer, but...
As the enginebay layout is broadly symmetrical (rad in the centre, hot manifolds both sides) wouldn't a more simple solution have been to have two identical fans that both come on at the same time? Result: quicker, more uniform cooling?
As the enginebay layout is broadly symmetrical (rad in the centre, hot manifolds both sides) wouldn't a more simple solution have been to have two identical fans that both come on at the same time? Result: quicker, more uniform cooling?
The temp that the fans comes on at is controlled by the ECU. To change the temps needs a new chip.
Joolz (trackcar) can do this. He's advertising on his new site (www.track-car-solutions.co.uk) for MBE twiddles over and above a remap.
Joolz (trackcar) can do this. He's advertising on his new site (www.track-car-solutions.co.uk) for MBE twiddles over and above a remap.
I have been watching the cooling carefully in my 4.5.
In France at Le Mans it didnt like the heat (40+ !!?).
In traffic it went to 115 at one point. Struggled to stay down at 100 and was often above that.
On Monday lunchtime I did M25 A1M etc- was a hot day. Car rarely went below 95. And was normally heading to 100 when traffic slowed. In heavy traffic didnt go above 105 and the fans brought down to 100.
So an upgraded rad seems to be the best solution to really help the cooling ie the fans seem to help but a better core would really help.
In France at Le Mans it didnt like the heat (40+ !!?).
In traffic it went to 115 at one point. Struggled to stay down at 100 and was often above that.
On Monday lunchtime I did M25 A1M etc- was a hot day. Car rarely went below 95. And was normally heading to 100 when traffic slowed. In heavy traffic didnt go above 105 and the fans brought down to 100.
So an upgraded rad seems to be the best solution to really help the cooling ie the fans seem to help but a better core would really help.
So your temp sat at 95deg when the traffic was flowing and gained 10-15deg in traffic on the fans?
sounds perfectly normal to me for a gauge that's over-reading by 10deg C.
stat temp is 84C, fans 95ish C. add the gauge error and you're bang on. Nothing wrong with your radiator at all I'd say.
sounds perfectly normal to me for a gauge that's over-reading by 10deg C.
stat temp is 84C, fans 95ish C. add the gauge error and you're bang on. Nothing wrong with your radiator at all I'd say.
trackcar said:
So your temp sat at 95deg when the traffic was flowing and gained 10-15deg in traffic on the fans?
sounds perfectly normal to me for a gauge that's over-reading by 10deg C.
stat temp is 84C, fans 95ish C. add the gauge error and you're bang on. Nothing wrong with your radiator at all I'd say.
Exactly what mine was doing till I rerouted the capilliary for the temp gauge. Now it reads great.
Thanks for all the advice.
I noticed this morning, when moving my Saab on the drive to wash it that the fans were on when I stopped, even after having had the engine running for only a minute or less. Perhaps they come on at low road speeds, not just high temp. I wonder how easy this would be to engineer?
Jon H
I noticed this morning, when moving my Saab on the drive to wash it that the fans were on when I stopped, even after having had the engine running for only a minute or less. Perhaps they come on at low road speeds, not just high temp. I wonder how easy this would be to engineer?
Jon H
jon h said:
Secondly, having checked it all out after the incident, fan coming on as it should at about 92 degrees (on laptop) but I think that is a very high temp to come in at, only 8 degrees off boiling.
As an aside, don't forget that the boiling point of a liquid is higher when its under pressure, so the water in the cooling system doesn't boil at 100degC.
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