Hybrid_From_Hell Posted October 8, 2006 Share Posted October 8, 2006 Hi all, Whilst I might know a thing or 3 on V8s I do need some help Basically I am trying to wire up the fans through a rad sensor to relays etc, and am trying to work out the following 1. What is the "Optimum" Temp a V8 should run at ? 2. What sensor should I run for Fans "On" and fans "Off" ? 3. I have a std Peugeout sensor, 2 pin I know there are loads of options but when should I set it to trigger the fans to come on, and then again, when to pop them off ? 4. Finally the info for the above is the sensor is fitted to my special rad on the passenger side at the bottom The hoses are : Top hose from themostat housing goes to the passenger top, the bottom hose goes drivers bottom to water pump Fitting is I think M20 What is the on / off as a starting point for heat to trigger start up and cool enough to then drop fans out ? Where the sensor is I THINK reads the engine coolant at one of the highest points in the - rad is this correct ? Quote Link to comment Share on other sites More sharing options...
mwncidur Posted October 8, 2006 Share Posted October 8, 2006 optimum must be somewhere near stat temp? boiling with antifreeze is 113 degrees. at a guess i would say fans on at 90 off at 89. i'm only guessing though. if it goes pete tong dont blame me. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 8, 2006 Share Posted October 8, 2006 optimum must be somewhere near stat temp?boiling with antifreeze is 113 degrees. at a guess i would say fans on at 90 off at 89. i'm only guessing though. if it goes pete tong dont blame me. What pressure cap is that running? Chris Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted October 8, 2006 Author Share Posted October 8, 2006 Oh Gawd I WAS going to say 20ish, but then remembered it has the later plastic RR Header tank that has the bleed hose that goes into the bottom hose to get ALL the air out, have no idea what the pressure of the plazzy tank assemble is but would serious doubt much different to say 20 +/- a tad ? SO far we have a 89/90 (which sounds wronmg to me) with a No Warrnaty caviat I was thinking around the numbers of coming on at say 92(ish) off at say 88(ish) bearing in mind I THINK ? the rad will be having its contents measured when HOTTEST ? HELP Nige Quote Link to comment Share on other sites More sharing options...
mwncidur Posted October 8, 2006 Share Posted October 8, 2006 82 or 88 stat? I am airing on the side of caution at 90. On my racer i use an isolator switch. once the stat opens, turn the switch...... fans come on, leave them on 'til the end of the race. not quite as practical on a road motor. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted October 8, 2006 Author Share Posted October 8, 2006 Thermostat Number I am unsure of, its an EFI 3.5 one, tho I have been advisede to fir the very early 74 degrees one out of the early 3.5 carbs by 2 people inc Jon W ........Basically 'I don't know' is the short answer Nige Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 8, 2006 Share Posted October 8, 2006 The running temperature should be set by the thermostat. IIRC 82 or 88deg on a V8 as stated above. If the engine (measured at the 'stat I guess) is getting significantly hotter than the 'stat temperature (and the thermostat is performing correctly) then your radiator/cooling system is failing. Running a pressure of, IIRC 15psi (usualy marked on the cap), will allow the engine to run at higher than 100degres without the water boiling - just the same as water boils at a low temperature at high altitude/low pressure. I would imagine that at atmospheric pressure the water in the coolant would boil at 100 degrees, ethylene glycol boils at 197 degrees. Remember the geyser of coolant the pikeys make at playdays when the rad is choked with mud and they overheat their £200 range rover and then remove the cap? The water all boils the instant the pressure is relieved. Chris Quote Link to comment Share on other sites More sharing options...
TJ101 Posted October 8, 2006 Share Posted October 8, 2006 Nige,, a thread i am looking at presently,, May help !!! Fitting rads By JST ? Quote Link to comment Share on other sites More sharing options...
MJIbex Posted October 8, 2006 Share Posted October 8, 2006 Nigel, I've used 1 one the SPA gauges for the past 4 years which I find very useful for a number of reasons (ps. had to get an adapter made to mate to the oil pressure on the rover V8). http://www.spa-uk.co.uk/design/productdeta...ct=DG%20200|365 It allowed me to see the exact temp that the V8 was running in the 90 (standard 3.9 on injection). I ran a 88 degree thermostate you could see it open on the temperature gauge. On standard 3.9 injection the engine did not like running past 113 degrees and would lose all torque, (only happened with a very blocked rad, and at this temperature did not get as far as blowing the pressure cap). I would not normally let temperature go past 108. You can also set the gauge to operate the fan at an exact temperature to suit requirement which is what I now use on the diesel. Back to the 90, I used a single 16 inch kenlowe wired into a V8 Discovery or V8 Range Rover (air con model) thermostate housing with the standard aircon fan switch. I could see this switch the fan on at 96 degree and would switch off again at 92/93 degree. Driving off road the engine would normally stay sub 100 degrees until the rad becomes blocked. This arrangement worked very well in my 90 and was very reliable. Quote Link to comment Share on other sites More sharing options...
western Posted October 8, 2006 Share Posted October 8, 2006 Oh GawdI WAS going to say 20ish, but then remembered it has the later plastic RR Header tank that has the bleed hose that goes into the bottom hose to get ALL the air out, have no idea what the pressure of the plazzy tank assemble is but would serious doubt much different to say 20 +/- a tad ? Nige Those caps are rated at 15psi, least the one on my 110 is. Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 8, 2006 Share Posted October 8, 2006 Nige, Your cap is 15psi & the stat is (or should be) 88C…….. so the running temp will be 88 – 90 and the boiling point assuming 50% coolant will be around 118 – 120 C Ian Quote Link to comment Share on other sites More sharing options...
Jon White Posted October 9, 2006 Share Posted October 9, 2006 I run mine with an 88-82 degree one IIRC and the thermostat is 74 degrees. I found the best bet is trial and error till you get the correct temperature. I've got 3 or 4 different ones floating around that you're welcome to borrow to try and see if they're too hot or too cold. I know what temp they are so you should be able to work out which way you need to go from there. Jon Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted October 9, 2006 Author Share Posted October 9, 2006 I run mine with an 88-82 degree one IIRC and the thermostat is 74 degrees.I found the best bet is trial and error till you get the correct temperature. I've got 3 or 4 different ones floating around that you're welcome to borrow to try and see if they're too hot or too cold. I know what temp they are so you should be able to work out which way you need to go from there. Jon Yes Please Dig em out ready Nige Quote Link to comment Share on other sites More sharing options...
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