[rescuehover]

Hi i am new to this forum and have a 07 plate 300 CRD the 3ltr V6 and i have a problem when i first set off, after about 10 mins driving the heating in the cabin goes cold and the temp gauge climbs into the red and puts the car in limp mode, after about 20 seconds the temp gauge drops to normal and cabin heating returns, whilst the gauge is climbing there is a clunking coming from under the dash for about 10 seconds and then it stops, I have fitted a new radiator and now a new thermostat but neither has cured my problem.
Any ideas guys will be much appreciated.at:

 

[jackwalton]

Have you had the water pump checked.

Jack

 

[rescuehover]

No water pump will be next, this problem only happens when I set off and I do about 1,000 miles a week ?

Paul

 

[jackwalton]

Are you saying it only happens the one time about 10 mins after each start and when you let it cool you can drive it normally?

 

[rescuehover]

It happens only once it has cooled down (4 hour stop maybe) but when it happens it goes into red and then drops off I don't stop it all takes place over about 30 seconds and then the temp gauge reads normal ? I can drive it all day and it wont happen again until it has cooled down? I suspect something to do with the heater circuit as there is a clunking from under the dash like a valve opening and closing?

Paul

 

[jackwalton]

It happens only once it has cooled down (4 hour stop maybe) but when it happens it goes into red and then drops off I don't stop it all takes place over about 30 seconds and then the temp gauge reads normal ? I can drive it all day and it wont happen again until it has cooled down? I suspect something to do with the heater circuit as there is a clunking from under the dash like a valve opening and closing?

Paul

I understand your symptoms now. I cant see it being the pump. Strange.
Wonder if theres an air lock ?

Do the cooling fans run OK as the temperature increases.
Both should be running well before the gauge gets high (About half scale on temperature indicator.)

Jack

 

[rescuehover]

Both fans run fine, in fact one is brand new as we thought that was the problem, I still feel it is something to do with the clunking sound from behind the dash?

 

[jackwalton]

Both fans run fine, in fact one is brand new as we thought that was the problem, I still feel it is something to do with the clunking sound from behind the dash?

I may be wrong but I cannot see the clunking behind the dash being anything to do with the cause of the fault, it is more likely to be a secondary symptom of the caused because the temperature creeps up too high and the pressure increases (poss water flashing off into steam).


If it was mine I would run the car from cold and just before the normal running temperature is reached i.e. just before the thermostat opens. Get out and check the temperature at the top hose to the Rad. As soon as the thermostat opens if the pump is working correctly you should feel the Hose suddenly get very hot and if you then squeeze the hose you may be able to feel/hear the water circulating through the Rad. After just a few minutes if the pump is circulating the water OK the temperature at the bottom of the Rad should slowly increase when the thermostat opens. If the temperature at the bottom of the Rad doesnt warm up you there is no circulation for some reason (Blockage or Pump).

I must admit it is very, very, strange that this only happens once when starting from cold and it will be interesting to see what the problem turns out to be.

Hope you get it sorted soon matey.

Dont want to throw you a red herring taking you along the wrong route and worry you without any foundation, but there is a Engine Oil Cooler in the Engine top Vee. If there was a leak between the oil/water sections I'm not sure what the implications could be. But either the water side or Engine side would have signs of oil or water in depending on which was the higher pressure (Normally expect oil in water). I havent heard of any failed coolers though.

I'm no expert on cars and yours is a very strange fault. I mention the oil cooler without any past experience or knowledge of failures (apart from oil leaks over the engine due to failed seals which have been upgraded to Viton). But these seals would be unlikely to cause your symptoms, they would just allow oil to pour over the engine top.

Alternative: Head gasket Leak ?

Jack

 

[jackwalton]

Manual says remove 2 clips and remove thermostat bleed hose when filling system but I assume air cant be your problem because it appears it does run at normal temperature after the initial rise.

Are you certain the thermostat is Ok and its the correct one for the car because the correct thermostat allows circulation through the pump at even low temperatures via a bypass valve in the stat.

EDIT:

Just read your symptoms again and I didn't fully appreciate what your symptoms were. >>>>>>> Temp abnormally high for only for about 30 seconds then drops and runs normally without having to shut engine down. Does the clunking only happen after the temperature is abnormal or before the temperature rises ?

Personally I would suspect an air Lock or faulty/incorrect thermostat or blocked expansion pipes ?(Even though I accept you have changed the thermostat).
I assume the system fills ok from the expansion tank ?

There are 3 hoses to the tank I believe I would be tempted to check all 3 are Ok (One is the feed to the rad and the other 2 are expansion pipes)
Don't forget its special HOAT antifreeze for the diesels.

 

[jackwalton]

I know I've been rambling a lot while typing BUT I've been giving it some thought: I would go for checking the 3 pipes are clear on the header/expansion tank first.

Should be easy to prove if you can get at em (Many bits aren't easy to get at on ours)

 

[rescuehover]

Hi Jack water flows through expansion ok, the clunking sound happens as the temp rises from normal and only lasts for 10-20 seconds and temp round town takes 1-2 mins to go up, my mechanic has now found what may be a valve on the heater circuit that may cause the clunking sound? there is no water in the oil or oil in the water and I am not loosing water, this is now causing me to think about getting rid of this car but it is so nice to drive and my brain keeps telling me it will be sorted soon, thanks for your help.
Paul

 

[jackwalton]

It does sound like a nightmare to fix, hope your sorted soon buddy.

Even if there is a valve that's clunking on the heater circuit (And I cant see one described or identified in the manual). I cant see how a heater valve could possibly cause the engine temperature to rise ? Flow should still be normal around the block and there should always be flow via extra bypass port on the thermostat even before the thermostat opens.

Please keep us informed.

 

[rescuehover]

Thanks Jack I will let you know when we find the problem.
Paul

 

[devilmaycare]

Just in case there might be an air lock, it might be worth trying to "burp" the system as per this recommendation: http://www.300cforums.com/forums/general-discussion/166625-how-hot-should-get.html#post1868729 Different engine, but might work. The ultimate solution in this case turned out to be a new radiator.

 

[rescuehover]

Hi Guys, not trying to temp fate but my problem has now gone away? we put an air line on the by pass line and shifted something (we think the pipe that passes beneath the engine may of had a restriction as first time trying it took about 15 seconds to pressure up but the second time was almost instant?) there is now no clunking noise from under the dash and the temp stays just below the half way point.
Thanks for all your help.
Paul

 

[jackwalton]

That's partly good news but I would give system a good reverse flush with water.

Cant understand the 15 secs compared to instant bit. Should have been done by blowing through an open ended system not a sealed system ?


Jack