Anyone fitted a lower temp thermostat? M62

**FisherX** · 22nd April 2019, 11:25 AM

G'day Guys,

So my issue is that the other week I towed my XJ Jag back from Gympie to Hervey Bay, and just as I got out of Maryborough the gearbox went into limp mode where it wouldn't get past 3 gear at 100kph. Now I know that is caused by gearbox high temp.

I was looking at adding an extra gearbox oil cooler in the future to keep the temp down. (The trailer would have been near the 3 tonne mark)

But I drove back to Gympie the other day without a trailer and hooked up my scanner to monitor the gearbox and engine temp on the way down. HOLLY CRAP I didn't expect the engine to level out at 118 degrees on the highway! It was steady at 105 degrees on the way from Hervey Bay to Maryborough, so I thought "a little high for my liking but ok" but when I was at a steady 100kph on the highway after 5 min she steadied out at 118 on the engine and 119 on the gearbox. Now that is too much for me. The cooling system is fine with no issues, fans are working, no leaks and plenty of fluid.

So I'm now looking at dropping my engine temp instead of the gearbox. I seen a 80 degree thermostat conversion online for about $120 from the EU but has anyone tried it and does it work? Or any other ideas for lowering engine temp will be appreciated.

Cheers Steve

**p38arover** · 22nd April 2019, 12:16 PM

I converted mine to an 88 deg C thermostat a few years back. The engine never gets above 99 deg even on 46 deg C days.

Start reading here: YAY!...now im overheating! :(

Having done this mod, if I was doing it again, I'd buy the ready to bolt on 88 deg thermostat and housing, e.g., Behr 2.548.88 It doesn't have the heating element of the original.

See fullfatrr.com - View topic - 4.4 Thermostats - could it be this easy for a lower temp ?

BMW thermostat.jpg

**Eevo** · 22nd April 2019, 12:39 PM

what temp is the stock thermostat?

**FisherX** · 22nd April 2019, 02:30 PM

As far as I've read the original starts opening at 105 and fully open at 113, plus it has a heating element to allow more cooling at high engine demands. (which you would think it would with a 3t trailer on it)

**Eevo** · 22nd April 2019, 02:34 PM

105? thats nuts!

**Homestar** · 22nd April 2019, 05:44 PM

In this sort of application yes. We have large generators with 105 degree thermostats in them as some modern engines simply don’t run efficiently until they are over 100 (and probably has something to do with emissions too). Had a couple of 650kva’s sitting happily on 110 degrees all day at the Airshow - they were at about 90% load on a 40 degree day. Wouldn’t feel comfortable with the same in my car though.

**knares** · 8th May 2019, 11:17 PM

i bought the BMW one 87deg
BMW wanted $180 for it, none in Australia as it wasnt in any vehicles released here.
bought it in Germany, aftermarket, 80 pound delivered

**NUTTTR** · 26th May 2021, 07:26 PM

Where did everyone buy their thermostats from?? I cannot find one for a reasonable price (and not from Lithuania)

**irubix** · 26th May 2021, 10:43 PM

Lithuania.

**NUTTTR** · 26th May 2021, 10:47 PM

LOL!

I haven't trusted those ebay sellers... But maybe I should then! Seems odd that Lithuania would have a non-rip off product available when no one else does...

Also, water pump (gates) ~160... Thermostat.... > 200?? Seems expensive. My current thermostat seems to be open too often....maybe I should just drill it out...

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