Personally I don't think keeping the coolant temps down won't solve the infamous "engine wiring bake" problem....although it surely can't hurt :-).

IMHO the main thing is routing the wiring looms so they aren't resting directing against the engine and buried in the Vee.

Cheers
DD

 

Nor do I- it may even do the opposite. Cooler engine temps means that more heat is being rejected from the radiator into the surrounding air rather than going out the tailpipe. This additional heat under the hood might accelerate the problem, not lessen it.

 

wow didnt think this thread would get this much input. The cars back together and i think itll run fine. I just get very different info about whats good for the car. For example my car will run about 3/4 up or a bit less (IE past the normal spot) and then the fan kicks on or the stats open and it very obviously drops down to normal or below that.

I just hate that if i am on that threshhold it will stay above normal because its just a degree or 2 aware from cooling down.

But maybe i am just tricked into being scared by all the people who say ZOMFG IF IT SNOT ON NORMAL YOUR ENGINE WILL BLOW UP.



just so everyone knows....my thermostats were broken for quite a while and my fan relay was as well but i still drove the car because the amount i was driving it didnt get the car warmed up enough until i turned around to go back home. I did fix the problem eventually though. I have seen my car pegged on H multiple times until it blew the heater hose and my engine is not broken and i did not drop a valve. These engines are more resilient that most give them credit for.

 

Pretty amazing, huh? Just try asking 'which oil is best'. No, best not.

 

yes but this is heat that has been dissipated into the air instead of staying in the engine. This air can flow out from the engine bay, but if the heat is in the engine its going to stay there.

as for the wires its like this...Which is worse?? Sticking your hand inside the oven when its heated up and feeling the hot air or touching the wire rack??

 

No heat stays inside the engine, it all comes out in three ways-

1) work that turns the wheels
2) waste out the exhaust
3) waste rejected through the cooling system

If the balance between any two or all three of these is altered- let's say more heat is directed to the cooling system because we wish to reduce coolant system temps- this radiated energy will increase the temperature of the engine bay, or in your example the air OUTSIDE the oven. The hotter that temperature, the more likely wires will become damaged out.

Continuing the oven analogy, the sole purpose is to heat the objects placed inside. If it's all lost by leaving the door open or through thin uninsulated walls it's pretty hard to cook the food or push the pistons.

 

not this again. if what your saying is true, then there has to be a balance between the amount of work that the extra heat does, and the amount of work that a more dense charge does. and i dont think 200*F is that balance.

lets take this for instance. when the May cylinder head came out, Jaguar found that extended periods of 125+mph speeds, such as on the autobahn, would create hot spots in the cylinder heads and cause predetonation issues, resulting in an engine that wouldnt shut off. these hot spots transferred enough heat in an "unappreciable amount of time" to cause predetonation. explain that.

no, dont. it IS an appreciable amount of time. period.

you reduce heat so that you can run leaner, more timing, more boost, more compresion, more dense mixtures.

AFR > Timing > Boost > Compression > Demsity > Heat.

 

Nope. Sorry.

BTW- there's no such thing as 'predetonation'. There's 'detonation' and there's 'pre-igntion'- two separate and distinct phenomena that have little to do with each other and certainly NOTHING to do with the OP's question. Please stop hijacking.

 

what your saying is that an engine will radiate heat through 3 ways, and reducing the temperature of any one method, increases the temperature of the other two. this would be true if you were reducing the temperatures of any of these methods of heat transfer by making them less efficient.
making anyone one method of heat transfer more efficient reduces the temperatures of the other 2, thus reducing the temperature of the engine.

if you start off with a hot engine, you need to transfer a lot of heat through the radiator, exhuast, and air to cool it down.

running a colder thermostat means starting off with a colder engine, which means you dont have to transfer so much heat to cool it down, resulting in a cooler engine bay, a cooler exhaust, and a cooler cooling system.
wow, just when i thought you couldnt be more wrong.

im gonna go put a colder thermostat in my grand prix, and drop another 0.10" off of my blower pulley, because it works that way. excuse me.

 

Sidescrollin-

I re-read you message and may have misunderstood your analogy of the hand in the oven. If you're stating that the object touching the wire rack will 'burn more' because the rack is hotter, this is not true- the racks are at exactly the same temperature as the air in the oven. A bare hand will simply burn sooner if touching the rack because heat transferred by conduction generally moves more effectively than by convection or radiation. An object left in an oven will eventually absorb enough heat to equal the air temp surrounding it. Ovens do most of their cooking by convection and only a limited amount by either radiation or conduction. An oven with a pizza stone changes this balance so that much of the cooking is done by conduction instead of convection.

In the case of wires in an engine compartment (to be on topic) most don't actually touch the engine so are heated exclusively by a combination of convection (hot air) and radiation from the engine and the radiator to a lesser degree. The act of running the engine at a lower coolant temp means that MORE heat would be dumped from the radiator into the engine compartment raisng the temp of the air surrounding the engines and wires not lowering it.

To your point of the wires touching the engine having an abbreviated life- I can only question the quality of insulation used by Jaguar at original build. I have other cars and bikes built in the 60s and 70s with original wiring harnesses. No signs of deterioration on those even the wires that lie directly on the engine.

 

well i have a different problem,, running very cold,, in the morning,drove 50 miles , my digital temp gage said only 160*F, sensor pickup mounted in left rear of cylinder head!

on trip back, mid afternoon, it only came up to 175*F, 50 miles also.

i'm wondering about the thermostats, factory dash gage about 1/4-1/3 up.

actually i think i'll leave it that way,, i dont drive it enough to ever wear it out from cold temps, YES, i do know about the technical aspects of it.

 

wrong.

running an engine at cooler temperatures means there is less heat altogether. less exhaust heat, less coolant heat, less convection heat.

if you, however, run an engine up to, say 200* and then try and cool it back down to 160* very quickly, you will put way more heat into the engine bay, more heat into the exhaust, and more heat into the coolant trying to cool the engine down.

if you start off with a lower operating temperature in the FIRST PLACE, then this never happens and you will have lower air temperatures, lower coolant temperatures, and lower exhaust temperatures.

look at it this way, if your driving at 200mph, and want to slow down to 160mph very quickly, your brakes get hot. if you start off at 160mph, and then maintain that speed, then your brakes wont get nearly as hot.

you just said it yourself! your cooling system isnt going to be spitting out 200* air when your engine never exceeds 160*. period end of story.


perhaps you dont understand what a thermostat does? it doesnt make the cooling system more or less efficient, and it doesnt make the cooling system exchange more or less heat. the only thing it effects is the standard operating temperature of the engine. a 190* thermostat is designed to force the system to maintain 190*. a 160* thermostat is designed to force the system to maintain a 160*.

 

I agree, Jaguar used gerneral purpose wire with plastic insulation, this will never last even with mild temperatures over a prolonged period of time. Most other manufaturers use hi-temp insulation under the bonnet, BMW for instance use silicone insulation this will almost last forever.

 

My experience says ...

No thermostat-you will overheat

better method of removing heat-add additional electric fan if room,
thicker core radiator if room and run a SLIGHTLY lower temp thermostat