Getting Hot Under Load

I have a 300tdi and have had this issue twice now, its seems to get very hot when the revs are held high for a long period.

First time was whilst stuck and i recovering myself with my winch, i was revving the crap out of it trying to get out and i noticed the temp needle working its way upto the red, backed off the idle for a while and it came down.

2nd time was yesterday going up a steepish hill on the M20, 3rd gear, about 3k and halfway up the needle was just below the red, got to the top and it started to come down.

All other times the temp is rock solid and just under the half mark on the gauge. Does 60ish on DCs fine and is even ok in traffic. Heather red hot all the time.

Rad is about 2 years old as is the coolant and head gasket.

Viscous fan is fitted.

Any ideas?

Iffy viscous coupling or rad maybe.

Ill be interested in advice you get on this, on my 96 tdi with aircon ive replaced the water pump and stat, flushed the heater and rad, and cleaned the fins, but it overheats still when towing a 1.5 tonne trailer up severe hills eg 30mph slogs for several minutes, ambient temp less than 20deg c, I thought they were "overcooled"?

Check coolant level.

Check oil level

Check the tightness of the serpentine belt (what drives the water pump).

Try turning the fan with the engine stopped (and the keys OUT of the ignition !) - it shouldn't spin freely. If it does, the VC's dead. (Of course, it may die in the locked-up state, but that will leave you over-cooled if anything).

Take the grille off and if there's anything blocking the airflow to the rad, clear it out.

Check rad's not full of mud and leaves.

Are the rad and hoses hot when this happens (i.e. is the 'stat tripping)?

If it does it again, turn motor off, count to 10, and restart. Almost instant descent of the temp gauge to cool would indicate an airlock being shifted.

Levels are fine, did the old 'dont try this at home kids' stopping the fan whilst the engine is running and the fan is fine.

Rad is not 'full' of mud mut its not clean either so will give that a blast with the jetwash later

Both hoses are red hot so stat opening.

I had similar .. take the rad/fan shroud off and check the fins at the back for any missing. It often only takes a few to screw with the rad. They usually look fine from the front, but it's only when you see the back properly that you can get an idea of how bad it actually is!

I had this, mine was a cheep crap plastic water pump, or check the rads not full of mud.

There is also a small thermostat that opens up when hot to let oil into the oil cooler. It is in the housing that holds the oil filter. If this late in opening or stuck closed your water temp will get hotter than normal.

Regards .

Jonathan

jonathanp said:

There is also a small thermostat that opens up when hot to let oil into the oil cooler. It is in the housing that holds the oil filter. If this late in opening or stuck closed your water temp will get hotter than normal.

Regards .

Jonathan

Click to expand...

Never knew this might check mine

If yr oil cooler pipes are both hot does it mean the thermostat is ok? Is that how you eliminate this as a possible cause? I just ordered a new viscous coupling from paddocks to eliminate that.......