The Ford Mustang RHD oil cooler, certainly non Mach 1 cars anyhow, have a small lesser known habit of bursting the water cooled oil coolers which at best is annoying and leaves a mess of coolant and oil mix on the ground and requires a tow home and new cooler (which can and has been proven to do the same trick all over again) or worst case it mixes the oil and coolant together and the first you know of it is when the smoke comes out of the bonnet. This has been known to break engines, completely break them requiring a whole new engine swap. That is not cheap. Not in the slightest. Even during OEM mechanical and drivetrain warranty period there is no guarantee that Ford will replace the engine for you as it is a lesser known issue. Thank you for your custom and goodbye. Of all the parts lying in Fords part bins, they chose that style of oil cooler. That's unlucky, really unlucky.
So what to do. Let us start with what i did and why i did it.
I removed the OEM coolant cooled oil cooler for a Mishimoto blanking plate and sealed up the coolant system a coolant bypass pipe. Why? Well because I do not track the car and it is not very warm very often up here. With 7 and a bit litres of oil flowing through the system and a chunk of that in the sump being cooled by the air flowing past it the conventional wisdom said the oil cooler was not needed. So, before 5yr warranty expired (though see above) I did the oil cooler bypass. And i was happy as the oil temperature gauge in the dash had no difference while in use (nor had it in any of the 10+ cars done before mine) and has been for oo six months or so.
What are the other options out there?
Well one could fit a newer coolant cooled OEM GT RHD oil cooler from Ford but again its the same issue. These things have been known to fail on 5k mile cars or 30k mile cars so um yeah that's a problem merely waiting to happen. Or not. This is the big dilemma.
One thought is to replace the entire coolant cooled oil cooler system with an air cooled system and fit direct replacement coolant bypass pipe to seal up the system. Having seen a few of these designs, one must chose carefully as some fit fairly small oil coolers right in front of the air condenser unit but have issues with oil pipe routing and have broken pipes on cars they got fitted too. Yep, the fix breaks the car, it's rare but it seems to happen. Also, some have reported that the air to air coolers are not big enough but most of these folks are doing track days / autocross which we'll come back to later.
Another thought though does require even more fabrication is to put the oil cooler system from the GT350 or Mach 1 into the GT and voila you have OEM parts fitted that are actually proven. Small issue of the bumper not having appropriate cooling ducts but you know that can be got round if one is going this route.
But the oil cooler isn't needed is it since the onboard oil temperature gauge is behaving no different from before. That's right yeah ? Or is it..
There is an onboard oil temperature gauge and and this has shown difference in readings that deleting the oil cooler makes and replacing it with a simple plate to complete the circuit. Those previously mentioned track cars have however shown that the oil temperature gauge fitted to the cluster is in fact not accurate because it is an inferred reading and not read from the oil itself. This inferred reading relies on the OEM oil cooler being fitted and it has no idea you've done something different and so its algorithm does nothing different and punts out the expected value. This has caused some track addicts to have issues when the Cylinder Heat Temperature rises, which is a directly read value, the oil temperature algorithm does its thing and increases the reading of the oil temperature. It keeps rising as the CHT rises and then limp mode conditions are hit as the car tries to save itself, which is nice. Problem is, these folks have fitted big oil coolers with proper actually reading the oil itself gauges and they are nowhere near the inferred value for the oil temperature.
But what if one is not tracking ones car and is merely driving about well within the limits of the car. How hot does the oil actually get? Does it really need that oil cooler at all?? Is that inferred gauge actually reading correctly. First off, it's a needle going across the sweep, white area for stone cold, green area for normal, yellow for a bit toasty and red for pull over and freewheel for a bit. There are no values for this gauge so it's not anything like an exact science. This is the gauge, cool eh?
So one day not that long ago someone who as done the exact same work as me decided to fit (12GBPound amazon special) oil temperature gauge to his car and go for a run. He did some 30zone stuff, dual carriageway then some shopping (car stopped obv) then some motorway driving and then some town road stuff and home. His oil gauge was showing 120degC within 2miles of starting and then putt putting along the motorway........................ That's not great. 140degC sitting at idle after said run. Holy Moses....
So after much faffing about i got myself a Stack oil temperature sender and gauge and stuck it in the glove box pointing towards me. Not great but so far, 90degC while moving in traffic along the motorway, in normal urban driving ish 90degC also. I have re-positioned the gauge and stuck it (gravity mainly) ghetto style onto the centre console so I can see what is happening while driving. Need to get fuel tomorrow so will do some more checking but until i can wind this thumping big v8 into the upper rev range, I doubt I'll see anything over 90degC. The fact it is like 3degC outside doesn't help either.
Pity the car can't display cylinder head temperature and inferred oil temperature at the same time and nicely within a camera view finder (which i dont actually have) of my oil temperature guage so we can compare everything at the same time. It does make you wonder about that 12GBPound amazon gauge used before..
