I was wondering if anyone here has done anything to improve the oil cooling on their XJS? or fitted a seperate radiator on a coolant line such as an aftermarket fan+rad unit or oil-to-coolant heat exchanger?

I have a bit of free space behind the body panels in my car after removing some things like the fuel vapor canister, I was going to have a body shop add vents or gills like you see in newer cars on the very edge of the car below the front bumper and fit something in there, possibly relocate my coolant filter or some other aux fan/rad combo unit there.

 

You could move the power steering cooler as well as fit a transmission cooler instead of the combined coolant/ATF radiator.

 

Nope.

Stock system works just fine down here.

I did remove the steer cooler, and removed the trans crap from the radiator.

The steer went without, the trans got an aftermarket universal cooler core under the front bumper, and that took a HUGE load off the coolant.

 

Good to know, I forgot about the trans. I'm going to have to measure the avg coolant temp before and after once a separate trans cooling system is fitted, I'm sure it'll be interesting.

 

Yep, most ATF fluid systems "operates" at about 100c, oops.

 

The colder the ATF can run at, the better it is for the transmission. Around 35°C is a healthy number - as that is where other transmissions are kept. Also Dexron II and III doesn't really like high temperatures.

 

That is why I used Full Synthetic ATF for a very long time in transmissions and steer systems for a very long time.

I agree with those temps, but it does not take long for a trans to raise its fluid temp very quickly. .Open highway in top gear, cool as it gets, traffic, firm driving etc all have a temp increase very quickly.

 

Exactly. When I get my TH400 into my car and all running again, I'll be doing a few little alterations to the ATF cooling. I'll be using a thermoswitch activated fan on a little radiator only for the transmission. Goal is to keep the ATF below 50°C at any time.

The power steering cooler is fine as it is. I'm just not sure if I should go to full synthetic or use a standard Dexron II/III. Probably full synthetic...

 

I'm a little confused. I just double-checked and there is an engine oil cooler in my car. Is this about replacing it with something better?

 

There is, so I'm a little confused as well.

Jaguar used both a full-flow cooler and a by-pass oil cooler. USA cars and some others got the by-pass cooler. The rationale, I think, was to prevent the oil from being over-cooled. One of the guys here -- Greg or Daim I think-- did quite a study on oil cooler effectiveness but, to be honest, I can't remember the details of the conclusion. Worth searching the archives for.

Cheers
DD

 

Basically, oil coolers without a thermostat won't do any good. There is really very narrow range of temperature where the lubrication is best (a little wider for synthetic oils, but not much). Keeping oil from reaching the optimal temperature with cooler is no favor to your engine.

 

Erm, the V12 reaches it's oil temperature really quickly. The oil cooler really drops the temperature. Especially as Jaguar intended the oil to be used as a coolant in the V12. Which is why higher speed countries (basically the rest of the world apart for the States) all got the full flow cooler.

 

Asking, not arguing.....

Where does 35ºC come from as an ideal temperature? That's quite low. Typically ATF runs quite safely in the 75-90ºC range.

I'm sure there's a 'designed' operating range for (let's say) Dexron III although I couldn't quickly find the specs. I know that one of enhancements of the Dex III spec, eons ago, was improved low temperature performance....implying that a too-low temp might not be entirely desirable. Back in the early 90s, when electronic shift transmissions were being introduced, many were designed to hold lower gears longer when cold for the specific purpose of getting the fluid up to xxx-minimum temperature, again suggesting the colder isn't entirely desirable.

IMO, the most important thing, especially if using non-synthetic, is to keep the temps below 110ºC as that's when the fluid begins to degrade, and quite rapidly !

In my heart it's hard to argue against keeping the trans cooler but I wonder if efforts to keep it ultra-cool are one of those "....point of limited returns...." type of things?

Cheers
DD

 

That figure seemes very low. I myself was quite surprised as I was told by a ZF transmission specialist, as I was having my 5hp24 upgraded. That is the temperature at which common ATF reaches it's highest 'expansion' point. Of course it will run hotter when driven hard BUT then again, it is a number per development.

 

We are not talking about the same thing. My point was about controlled oil temperature, it is beneficial. You tell about "dropping the temperature", uncontrolled I assume? This is exactly what I do not want to happen to my engine. There was an extremely comprehensive research on Porsche forums. The conclusion was: keep it as close as you can to 85-95° C.

 

I understod you mate, i just see no reason to have a regulated oil cooling per thermostat/valve... Especially not with all the oil in the oil system... But heck, improve all you want on a tried and proven setup

 

my trans cooler gets plenty of air!

 

Nice place Ron! I was thinking of putting one behind the lower grill... Maybe even directly infront of the oil cooler...

 

AFAICS part of this thread is discussing automatic gearbox fluid temps, and part engine oil temps. I know nothing about ATF temps, except to say that using Grant's type cooler the stuff never gets too hot as far as I can see.
Concerning engine oil temps:
As Doug mentioned, I did some pretty careful measurements of engine oil temps on my V12 bypass oil cooling engine. This was because I had a project to change it to full flow and I wanted to see what the engine oil temps were. results as follows:
Temp strips on the sump; the oil filter block, the oil distribution casting on top of the engine at the rear of the V; the cam covers; and the input and output side of the oil cooler.
Tests done in hot summer weather (say 33C shade temp) and over a fast road test lasting an hour or so. Results:

• Hottest was the cam covers at 90C max
• oil cooler took 20C out of the temperatures
• everywhere else 80C to 85C never higher.

Just about perfect, so I have scratched the full flow "upgrade". Short of track racing I cannot see how oil temps in road use will get much hotter than that.
Greg

 

i have seen many automatic transmissions , burned out and slipping , not shifting properly, from overheating!!

never seen one from running to cool, i suppose maybe with a oil cooler radiator the size of the engine coolant radiator?

Nope aint worth the paper to write about it!!

ron