I'm at my wits end with the coolant on my MY2012 4.4 TDV8... Any help, advice is greatly appreciated.

Engine runs as it always has, smooth and quiet until the temperature gets ove 100c.

Pootling around town at 30 mph the temperature runs at around 107 to 107c. As soon as i drive up a hill the temperature rapidly rises to 155c and above and the temperature guage moves to the right close to the hight hand marker.

On the motorway on a flat stretch at around 60 mph temperature runs to around 107c, upon even the slightest accelerattion to 70 mph the temperature quickly rises to 115c plus, with the temperature guage again moving to the right of the scale. When on cruise control and the temperature reached 115 it cancels cruise control.

When I put the heater on maximum heat and the blower on maximum the temperature comes back down to around 107c at around 60 mph.

1. No coolant leaks.
2. No pressure loss (Pressure tested when cold and hot, no pressure loss or leaks).
3. After a run as describe above I have noticed that the top hose collapses when the coolant has cooled, as if a vaccum had been created in the cooling system.
4. No oil leaks or loss,

I have had the front end on ramps and have burped the top hose for days.

Has anyone had a similar experience?

Again any help will be greatly appreciated.

John 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son

My top hose used to collapse and needed to be replaced. I also changed the expansion tank cap. Mine didn't over heat though. Caps are only a fiver.

The heater on max, and fans full dropping the temperature suggests that the system is able to dump heat through the heater matrix, but that its not doing that through the main radiator where it should be dumping the most of the heat in a normal manner.

Which then suggests that the hot coolant isn’t passing through the main radiator … thermostat stuck, or blocked coolant pipe.

Are the pipes running to/from the radiator hot? If you squeeze them do they feel like they are full ? V8 or else ...

I would be changing the thermostat without further delay.

Be aware that there has been a parts shortage of thermostat housing parts for a while so check you can get the part before you remove it. The thermostat housing is part of a bigger component and can’t be purchased separately however it can be replaced without removing the whole housing which makes it an easier job but still requires quite a bit of work removing fan and belts etc. I wouldn’t drive it in this condition either. 2012 TDV8 Vogue (L322)

Many thanks to all for the advice...

Comments noted. I did purchase a new thermostat from Rob at Duckworths a couple of weeks ago so its time to fit that.

Whilst doing so I will drain the cooling system via the bottom hose, hopefully its only the thermostat. Belts and rollers were all done about 6 months ago. and the waterpump is not leaking, so don't expect any issues with those components. I just wish I had replaced the thermostat at the same time.

Will report back if the thermostat replacement solves the overheating issue.

Again, thank you all for your input.

John 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son

I'm another who didn't think to change the thermostat when changing the pulleys and belts. I did change the water pump though.

I would check belt tensions as well to ensure water pump is being driven ok. 2012 tdv8 Westminster arrived Jan 19 gone Dec 23

200 TDi discovery bobtail gone
RR classic v8 bobtail gone
300 tdi Discovery 3 dr gone

THank you for the advice...

The tensioner was replaced with the rest of the rollers..

Now waiting for some decent weather here in the South East as will be working on the drive... Looking at the weather forecast ists going to be rain, wind and low temperatures for the next week.

John 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son

Hi,

How did you get on with this issue, I’m experiencing exactly the same thing to my 2011 4.4 TDV8 - could you let me know how you rectified the issue?

It would really save me a lot of time and money

Many thanks in advance for your input

Lee

I changed the thermostat. The issue was the thermostat sticking closed. I had ordered a complete thermostat replacement from Duckworths, but these parts were on back order with no anticipated delivery date.

I was able to order the thermostat internals and disassemble the existing thermostat housing then replace the internals.

Undo the cooling fan assemby and turn the fan to the right.... Mine came off without needing to hold the shaft. A gentle tap with a hammer shocked it loose... I suppose it depends on who put it back on... no need to over tighten it. You can then move the fan towards the radiator suficciently to geive you enough rook to remove the thermostat housing.

There is a major design flaw with the plasitic thermostat housing in that the plastic tabs that hold the internal metal thermostat in place are likely to be very brittle and unless the old internals are removed and replaced very carefully, then these plastic tabls will break off and render the plastc thermostat housing unusable.

When you get the thermostat enclosure off take the enclosure to the tailgate. then find a suitable Find a large round piece of pipe, that fits over the metal thermostat internals, but between the two plastic lugs.

Then with the bottom of the thermostat housing on the tailgate use one hand to steady the housing and the other hand combined with your body weight to push the thermostat spring down and simultaneously twist the two metal lugs on the thermostat out from under the two plastic lugs of the housing, without stressing the plastic lugs. Needs quite a lot of pressure. The secret is to find a correct circular item that will fit over the top of the thermostat and not interfere with or stress the lugs.

When removing the old thermostat internals and replacing with new there is a special tool available to ensure that the pressure on the plastic tabs is managed and they are not damaged. Alternatively

You do not have to disassemble the radiator shroud as per the workshop manual. Instead, get the car up on rampts, remove the under tray and remove one of the two bolts holding the metal coolant pipe in place and slacken the second bolt off slightly. Then unbolt the thermostat housing and you will have enough wriggle room to remover the housing. Then you can either replace the thermostat internals as described above or the complete housing if you can get one.

If you do damage the thermostat housing tabs without a replacement housing being available then you can run the car without a thermostat, which should only be a short tern solution until you can get a replacement housing.....

Hope this helps...

John 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son

running without thermostat will overheat engine! You need blanking plate, to close short circuit.

My leaking thermostat

Click image to enlarge

No will not. Even damaged yhermostat if opens to radiator will restrict flow in short circuit. If you remove then water will flow where lower restriction is,so will go mostly back to the engin rather than long way through radiator.