75 CDT - Engine too warm

catakate · 18th December 2017, 19:28

Hi all,

At first, my CDT was too cold, hence the thermostat was presumed dead wide open anf a new in-line thermostat was fitted.

Less then 3.000 miles later, driving on the motorway in 1 degree above freezing, the temp gage almost gives me a heart attack! The in-line thermostat is immediately presumed dead shut and a cheap piece of rubbish. Pulled over, tools out, thermostat relocated in the boot, journey resumed, no change! Next thought, the Webasto has gone rogue and is cooking my engine. Pulled over, the exhaust is stone cold, pulled the power plug out while there and back to inspect the coolant. The top hose to the radiator is hot, radiator itself is ice cold. Coolant flows into the preasure vessel therefore not through the radiator?

Heating on 28 degrees with blower on full blast anf section 7 of OBD reports 85 degrees at idle with no FBH!!! Is it possible for a failed open thermostat to turn in its grave and shut the whole system?

If not, anyone has any ideea why is this engine so hot? ( other then being in love?)

While waiting for the garages to open in the motning, any help is hugely appreciated

Regards

COLVERT · 18th December 2017, 20:00

Hot top hose, rad cold.---

Two things spring to mind. No circulation ( Pump impeller )

Or main rad blocked.

Can't be the thermostat as you've removed it.

catakate · 18th December 2017, 23:46

Hi Colvert,

There is some circulation as the coolant flows into the expansion tank and overflows at the bleeding knob. Anything else comes to mind that could keep the coolant from going back into the engine, except for a blocked rad?

I haven't removed the original thermostat when the in-line one was fitted. The hot top hose excludes that as a possible cause?

pletevl · 19th December 2017, 07:22

isn't 85° the perfect engine temperature ?

grivas · 19th December 2017, 11:32

Quote:

Originally Posted by catakate

Hi all,

At first, my CDT was too cold, hence the thermostat was presumed dead wide open anf a new in-line thermostat was fitted.

Less then 3.000 miles later, driving on the motorway in 1 degree above freezing, the temp gage almost gives me a heart attack! The in-line thermostat is immediately presumed dead shut and a cheap piece of rubbish. Pulled over, tools out, thermostat relocated in the boot, journey resumed, no change! Next thought, the Webasto has gone rogue and is cooking my engine. Pulled over, the exhaust is stone cold, pulled the power plug out while there and back to inspect the coolant. The top hose to the radiator is hot, radiator itself is ice cold. Coolant flows into the preasure vessel therefore not through the radiator?

Heating on 28 degrees with blower on full blast anf section 7 of OBD reports 85 degrees at idle with no FBH!!! Is it possible for a failed open thermostat to turn in its grave and shut the whole system?

If not, anyone has any ideea why is this engine so hot? ( other then being in love?)

While waiting for the garages to open in the motning, any help is hugely appreciated

Regards

Have you fitted the in-line thermostat the right-way-round!!

clf · 19th December 2017, 12:10

Quote:

Originally Posted by pletevl

isn't 85° the perfect engine temperature ?

Quote:

Originally Posted by grivas

Have you fitted the in-line thermostat the right-way-round!!

I was thinking that too, leading me to believe that the original stat is still working. Along with an inline stat and working original, I imagine the temp will be warmer than usual for cycling periods of time.

Curious to know what the temp was prior to the removal of the inline stat.

Sent from my SM-A310F using Tapatalk

catakate · 19th December 2017, 13:25

Guys, thanks for all your thoughts and please allow me to restate the facts.

Before the in-line thermostat was fitted, the temp gage never reached the 7 o'clock mark.

In-line thermostat fitted and was all good for a few thousands miles.

At this moment in-line thermostat was taken out.

At idle with the heater off the engine keeps getting hotter and hotter.
With heater on, it goes to just under 90 degrees. In about 15 miles doing 50 mph on the motorway goes over 100 degrees and I have to pull over.

Anyone knows what is the temperature the cooling fan should kick in? Mine is presumed dead anyway, it doesn't come to life when the aircon is switched on.

I've been looking at the diagrams of the cooling system but can't tell for sure so here is the question: the original thermostat is blocking the coolant comming back from the radiator through the bottom hose, or have I got it completely wrong?

catakate · 19th December 2017, 15:10

UPDATE

Boy, am I glad to report this!

I now have a warmish rad and at idle the temp goes down to 76 with the heater on. Close to decent behaviour to me!
Looks like I might do more than 100 miles today

Can't wait to get to my garage and dismantle the whole thing, how about that for a Christmas project? Ha!

clf · 19th December 2017, 16:39

ideal operating temp for the diesel is around 88 degrees. idling or not, with or without the heater on. I would expect the heater after about 15 mins of idling (after reaching 88-90) degrees, to draw the temp down to 76 though, but maybe take up to as much as an hour to reach into the 80's whilst idling from cold with the heater on.

Going up to around 105 degrees, I believe is quite safe (and when the needle begins to rise above the mid way point) in the diesel, never got over 100 myself though.

Is your fan working? It should activate around 95-100 I believe, have only tried this once, and cannot remember when it tripped on.

I do wonder if the original thermostat had failed as we know it to. ie opening early. Or had only begun to break down, in that it was only opening slightly early (and still is). What temp was it reaching PRIOR to fitting the inline stat? I also wonder if the original stat has indeed failed, and has blocked up slightly with some sludge in the coolant? or something blocking the radiator? (In my experience with my failed original stat, 15 miles at a constant 50mph, with no acceleration etc, it would display around 70-75 degrees)

catakate · 19th December 2017, 17:49

clf,

Never had the time to check the temp prior to removing the in-line thermostat, it was too high for the lenght of my journey, I pulled it out as fast as I could.

Without the heater on max temp and speed, the engine just keeps getting hotter, I turned the heater on at 100 degrees, obviously something wrong somewhere.. Although a bit better at the moment, as per the update above, still can't find a speed to keep the engine happy and under 105 C.

No signs of life from the fan so far, unfortunately. I can only hope for the pipes tu unclog themself or I have another thousand miles to crawl from one carpark to the next

18th December 2017, 19:28	#1
catakate Newbie Rover 75 Saloon Join Date: Oct 2017 Location: Weston-super-Mare Posts: 23 Thanks: 3 Thanked 2 Times in 2 Posts	75 CDT - Engine too warm Hi all, At first, my CDT was too cold, hence the thermostat was presumed dead wide open anf a new in-line thermostat was fitted. Less then 3.000 miles later, driving on the motorway in 1 degree above freezing, the temp gage almost gives me a heart attack! The in-line thermostat is immediately presumed dead shut and a cheap piece of rubbish. Pulled over, tools out, thermostat relocated in the boot, journey resumed, no change! Next thought, the Webasto has gone rogue and is cooking my engine. Pulled over, the exhaust is stone cold, pulled the power plug out while there and back to inspect the coolant. The top hose to the radiator is hot, radiator itself is ice cold. Coolant flows into the preasure vessel therefore not through the radiator? Heating on 28 degrees with blower on full blast anf section 7 of OBD reports 85 degrees at idle with no FBH!!! Is it possible for a failed open thermostat to turn in its grave and shut the whole system? If not, anyone has any ideea why is this engine so hot? ( other then being in love?) While waiting for the garages to open in the motning, any help is hugely appreciated Regards

19th December 2017, 16:39	#9
clf This is my second home MG ZT CDTi Join Date: Jan 2014 Location: carrick Posts: 7,859 Thanks: 3,494 Thanked 2,657 Times in 1,973 Posts	ideal operating temp for the diesel is around 88 degrees. idling or not, with or without the heater on. I would expect the heater after about 15 mins of idling (after reaching 88-90) degrees, to draw the temp down to 76 though, but maybe take up to as much as an hour to reach into the 80's whilst idling from cold with the heater on. Going up to around 105 degrees, I believe is quite safe (and when the needle begins to rise above the mid way point) in the diesel, never got over 100 myself though. Is your fan working? It should activate around 95-100 I believe, have only tried this once, and cannot remember when it tripped on. I do wonder if the original thermostat had failed as we know it to. ie opening early. Or had only begun to break down, in that it was only opening slightly early (and still is). What temp was it reaching PRIOR to fitting the inline stat? I also wonder if the original stat has indeed failed, and has blocked up slightly with some sludge in the coolant? or something blocking the radiator? (In my experience with my failed original stat, 15 miles at a constant 50mph, with no acceleration etc, it would display around 70-75 degrees) __________________ It is not gloss primer .............. it is duct tape silver!

18th December 2017, 20:00	#2
COLVERT This is my second home R75 Saloon. Join Date: Feb 2009 Location: France/or Devon. Posts: 14,003 Thanks: 3,851 Thanked 2,167 Times in 1,816 Posts	Hot top hose, rad cold.--- Two things spring to mind. No circulation ( Pump impeller ) Or main rad blocked. Can't be the thermostat as you've removed it.

18th December 2017, 23:46	#3
catakate Newbie Rover 75 Saloon Join Date: Oct 2017 Location: Weston-super-Mare Posts: 23 Thanks: 3 Thanked 2 Times in 2 Posts	Hi Colvert, There is some circulation as the coolant flows into the expansion tank and overflows at the bleeding knob. Anything else comes to mind that could keep the coolant from going back into the engine, except for a blocked rad? I haven't removed the original thermostat when the in-line one was fitted. The hot top hose excludes that as a possible cause?

19th December 2017, 07:22	#4
pletevl Posted a thing or two rover 75 cdti(rhd), MG ZR(lhd), MG TF(lhd), MG TF(rhd), mini mpi (lhd), Renault megane III (awful) Join Date: Mar 2014 Location: East of France Posts: 1,282 Thanks: 124 Thanked 114 Times in 93 Posts	isn't 85° the perfect engine temperature ?

19th December 2017, 13:25	#7
catakate Newbie Rover 75 Saloon Join Date: Oct 2017 Location: Weston-super-Mare Posts: 23 Thanks: 3 Thanked 2 Times in 2 Posts	Guys, thanks for all your thoughts and please allow me to restate the facts. Before the in-line thermostat was fitted, the temp gage never reached the 7 o'clock mark. In-line thermostat fitted and was all good for a few thousands miles. At this moment in-line thermostat was taken out. At idle with the heater off the engine keeps getting hotter and hotter. With heater on, it goes to just under 90 degrees. In about 15 miles doing 50 mph on the motorway goes over 100 degrees and I have to pull over. Anyone knows what is the temperature the cooling fan should kick in? Mine is presumed dead anyway, it doesn't come to life when the aircon is switched on. I've been looking at the diagrams of the cooling system but can't tell for sure so here is the question: the original thermostat is blocking the coolant comming back from the radiator through the bottom hose, or have I got it completely wrong?

19th December 2017, 15:10	#8
catakate Newbie Rover 75 Saloon Join Date: Oct 2017 Location: Weston-super-Mare Posts: 23 Thanks: 3 Thanked 2 Times in 2 Posts	UPDATE Boy, am I glad to report this! I now have a warmish rad and at idle the temp goes down to 76 with the heater on. Close to decent behaviour to me! Looks like I might do more than 100 miles today Can't wait to get to my garage and dismantle the whole thing, how about that for a Christmas project? Ha!

19th December 2017, 17:49	#10
catakate Newbie Rover 75 Saloon Join Date: Oct 2017 Location: Weston-super-Mare Posts: 23 Thanks: 3 Thanked 2 Times in 2 Posts	clf, Never had the time to check the temp prior to removing the in-line thermostat, it was too high for the lenght of my journey, I pulled it out as fast as I could. Without the heater on max temp and speed, the engine just keeps getting hotter, I turned the heater on at 100 degrees, obviously something wrong somewhere.. Although a bit better at the moment, as per the update above, still can't find a speed to keep the engine happy and under 105 C. No signs of life from the fan so far, unfortunately. I can only hope for the pipes tu unclog themself or I have another thousand miles to crawl from one carpark to the next