My PUG 308's engine bay feels super hot - short or long runs!

L

Lofty

Member
Tadpole
Joined
Apr 30, 2021
Messages
68
Location
Queensland, Australia
Hi guys,
Here's a dilemma that I'm presently unable to solve on my 2008 PUG 308 Turbo 1.6lt petrol. Perhaps you chaps can 'lend a hand' in solving this 'nightmare'
  • the engine seems to get super hot, yet the Temp Gauge never exceeds =/- 90*C and the cooling fan never switches on !
  • The 'Haynes Repair Manual' states that the thermostat opens at 106*C - (so according to my Temp gauge, my thermostat never opens!). How is this possible??
  • My Coolant Temperature Sensor (out of the car) , reads 80*C /300 Ohms in a boiling water (100*C/180) Ohms experiment ?
Any way forward will be greatly appreciated
Regards,
Lofty.
Ipswitch, Qld.
 
My Citroen manual says the opening temperature is 105 deg, unless the engine computer opens it at 89 deg.

Another manual gives this chart for the temperature sensor (which operates on a 5V signal from the computer)-- NB logarithmic scale.
temperature sensor.png
 
when you say seems super hot, you are aware the turbo being in front of the engine and exhaust/Cat in the front means the front of the engine is always hot.

when you turn off the engine can you hear the turbo coolant pump running for around 10 mins?
how do you know the cooling fan never turns on, start car, press the ACond button fan should turn on.

Ive never tested the temp sensor as its difficult to reach being that it is behind all the main pipes and needs to be reached from turbo which is usually way too hot. there are 2 sensors you may have removed the one from the RHS on the thermostat?? cant recall what this controls,
yes the turbo version of the thermostat opens at 105deg, the non turbo is 89deg but has less connections so not interchangeable.
 
But when we first did training on this engine it was made known that the 90 degrees on the gauge doesn’t match up with 90 water temp apparently because customers wanted to see 90 all the time if you look at engine data on the cars it’s mostly always off by a bit.
 
dmccurtayne said:
But when we first did training on this engine it was made known that the 90 degrees on the gauge doesn’t match up with 90 water temp apparently because customers wanted to see 90 all the time if you look at engine data on the cars it’s mostly always off by a bit.
Click to expand...

Most cars since the 90s seem to have "normalised" temperature gauges. Which drives me nuts. I'd rather know how hot the motor is. Even the shitbox range rover I have here that is from back early 90's. I've had it upto 102degree by my accurate aftermarket temperature gauge. The dash one was still displaying around "normal". I was concerned, but not to much. I'd been running almost full load in 2nd gear up a steep climb for an extended period of time and it was 'holding' at around 100degrees. Given its a pressurised cooling system running coolant, remember it doesn't actually boil until 120'ish degrees.

The issue is you need to know. There is a lot of people that have destroyed motors as by the time the gauge shows "hot" .... and you pull over, its far to late. you weren't given any warning leading up to the overheating event. especially in the case of coolant loss.

If you look at the oil temperature gauge in the poogoe .... you may find its not normalised like the coolant temp. I've noticed it can climb quite high in the 407 here.
 
Yo there Seasink, dimistyle, dmccurtayne, DoubleChevron, thanks guys, your responses have been overwhelming. Wow, such positive inputs to helping find a solution!
Meanwhile I sourced a YouTube video in desperation, (it's such a MAJOR resource for us 'shade tree' diagnosticians), I think that my solution lies herein, check it out):

My answers your questions:
  1. I found a similar 'Temp Chart' (on the Net) - a very valuable Chart.
  2. Yes, I absolutely agree that the turbo and exhaust/Cat in the front means the engine is always hot,
  3. No, I've never heard my Turbo coolant pump running after switch off! Do you have a reference 'Link' to this as my Haynes Manual is soooo basic.
  4. My A/C is out of action, (compressor pump suspect), so I never turn A/C on, hence no 'coolant fan' action.
  5. Haynes Manual points to the CTSensor, (hooray!) so I believe I tested the correct unit.
  6. Thanks for your input 'dmccurtayne' - that's a point I never knew - seems so weird though??
  7. Thanks 'DoubleChevron' - I've taken your observations onboard .... very interesting!
In summary, as I'm not sure of the next step to a solution but to wait for a "MIL" (check engine light) to trigger (as the video clearly shows one will) and then start panicking!
Any further ideas will be greatly appreciated.
Regards and thanks,
Lofty.
Ipswitch, Qld.
 
The small electric turbo coolant pump runs after the engine is switched off, as the turbo is still hot enough to be damaged. You can hear it if you listen for it under the bumper. It makes a quieter and dfferent noise from the fan.
pompe.jpg
 
Yo Seasink, Thanks for your pronto 'follow up'!
Great diagram - is this in a manual that you have?
I'll listen carefully for sound of the pump on switch off, once I get the car running again.... hopefully within a week.
Ciao.
Lofty :)
 
Something interesting about the turbo coolant pump. Here is my translation of a test manual-
A diagnostic check is performed every time the pump is started. If there is over current at start-up (eg the pump is blocked) the engine computer will immediately stop it.
Click to expand...
 
DoubleChevron said:
The Range Rover I have here that is from back early 90's. I've had it up to 102degree [that's not overheated @ all] by my accurate aftermarket temperature gauge. The dash one was still displaying around "normal"[& that's correct]. I was concerned, but not to much. I'd been running almost full load in 2nd gear up a steep climb for an extended period of time and it was 'holding' at around 100degrees. Given its a pressurised cooling system running coolant, remember it doesn't actually boil until 120'ish degrees.

The issue is you need to know. There is a lot of people that have destroyed motors as by the time the gauge shows "hot" .... and you pull over, its far to late. You weren't given any warning leading up to the overheating event. Especially in the case of coolant loss [that example is usually a hose or something similar & not an over heated engine].
Click to expand...
People panic about this sort of stuff unnecessarily as they don't understand modern cooling systems & parameters that they work well within. That in many cases is well over 100*C these days with caps sometimes over 20# & most @ around 1 ATM.
So to stop folk panicking manufacturers have a normal zone where the vehicle is not overheating.

Rule of thumb is if it is not boiling [that means not losing coolant] it is not overheating!
Electric pumps & fans circulate coolant after shut down to normalize, stop hot spots & boiling. Their operation is very important.

If one overfills a coolant system & most DIY folk do, once heated, the thermostat opened, coolant expanded & cap pressure reached there will be overflow to an expansion tank & once its filled up with excess cooling that spills to ground. That is fine don't refill!
Once cooled the expansion tank level will go to normal & should be good until the coolant is due for changing.

The level going to the normal [min max] line in the expansion tank is because the radiator cap vacuum valve opens due to negative pressure when the coolant in the radiator cools, drawing back the excess coolant in the expansion tank to fill the space.

Another thing is when the coolant system is HOT squeeze any coolant hose & it will feel tight or taught meaning there is pressure in the system, all is good & there is no need to check anything. That check is especially telling one not to remove the radiator cap & get scalded with superheated steam. If doing this test & things feel squishy it means, the vehicle is cold, one has lost coolant or the radiator pressure cap is kaput.

DO NOT KEEP CONTINUALLY TOPPING up the SYSTEM or WORRYING ONES SELF UNNECESSARILY if the RADIATOR HOSES are TIGHT when HOT & THE OVERFLOW TANK is @ THE CORRECT MAX/MIN LEVEL WHEN COLD.

Not all systems operate in exactly the same way but the principles are no different from then till now!
Same principle & system used on SAS Desert Jeeps in WW2.
 
Thanks guys, all info, Iv'e taken it all 'on board' for sure......!
In summary so far:
  1. Excessively hot engine bay on switch off, suspected Coolant Temp sensor fault and cooling fans not switching on.
  2. Bad oil leak/s, dripping onto the 'exhaust' (smells to 'high heaven') .
Result:
  1. Ignore the 'over heating' suspicion until DTCode alerts otherwise.
  2. Removed Turbocharger & exhaust manifold - chasing oil leak/s - new parts on order.
Will discuss further action taken on Forum going forward.
 
Did you check that the turbo coolant pump works, and its fuse? See comment about AC above.
 
Oil leak will probably be from turbo oil feed pipe the genuine one breaks down at the swivel joint at the turbo end. The after market flexi hose style one not sure.

Also oil leaks from oil filler housing/ heat exchanger when oil gaskets go hard.

3rd location is the o ring from the vacuum pump on side of the cam box.

I'm pretty sure there is another oil leak from the turbo itself but I'm still tracking this on one of of 308s
 
Hi, your 3 possible oil leak areas, are totally 'on point'! Thanks.
I'm attending to all three locations on the motor.
  • I replaced that exact Turbo oil feed line 13 months ago for the very reason, you mentioned.
  • An answer to your 'flexi hose' conundrum:
I bought a 'flexi' oil feed line, as a replacement for the OEM pipe.
(Ebay - Mamba brand, made to fit PUG 308!), looked so easy to fit - guess what ?
  1. Flexi bore size is 3mm dia; OEM is 5mm,
  2. Length of pipe +/- 75mm too long. (Returned for a refund)
P.S. Ebay is your best friend against shoddy online products - they get a refund, for you every time!
So, back to replacement OEM Turbo oil feed line, and so expensive.
Thanks for the advice.
 
Hi Seasink, apologies for the delay in replying to your question, re: coolant pump working...
The motor is partly dismantled, I'll check on it when the car runs again. Thanks so much!
 
Lofty said:
Hi, your 3 possible oil leak areas, are totally 'on point'! Thanks.
I'm attending to all three locations on the motor.
  • I replaced that exact Turbo oil feed line 13 months ago for the very reason, you mentioned.
  • An answer to your 'flexi hose' conundrum:
I bought a 'flexi' oil feed line, as a replacement for the OEM pipe.
(Ebay - Mamba brand, made to fit PUG 308!), looked so easy to fit - guess what ?
  1. Flexi bore size is 3mm dia; OEM is 5mm,
  2. Length of pipe +/- 75mm too long. (Returned for a refund)
P.S. Ebay is your best friend against shoddy online products - they get a refund, for you every time!
So, back to replacement OEM Turbo oil feed line, and so expensive.
Thanks for the advice.
Click to expand...
OEM is the way to go for oil feed pipe, difficult to install in situ but Ive done 2 so far. without removing the manifold

heat exchanger/oil filter housing I have the BMW part number for the Mini cooper but need to go hunting through receipts. easy enough job when everything is off the front end. there is the o ring set on the block side and another set in between heat exchanger the housing.

Get the turbo checked while its out
 
Thanks for your interest and advice. Waiting now for replacement O-Rings to arrive.
New turbo = $2,400!
Happy day.
(P.S. Contacted 3 Turbo shops for unit check-up, all sent me away).
 
near new on FB market for 800, but the cassette insert are cheap, I would have thought simply testing at a turbo shop would be a no brainer but maybe they are only interested in $$$ upgrades?

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