Temp Gugae and fan cooling

[fuvureju]

Hello All

406 D8 Mk 1 1.9DT build April 1996

Recently, my temp gauge has struggled to make 80 degrees and usually sits around 70 degrees.
Previously, from new for the first decade it would hold a steady 80 degrees and that seemed to be the normal running temp for many years.
Eventually i had to replace the temp sensor that fed the gauge and also replaced some of the fan relays (and also replaced the bitron sensor at the same time)
Afterwards the car seemed to run hotter typically around 90 degrees and on a hot day even hot 100 degrees which had me concerned.
However, over this winter it has been running much cooler.

Does this sound normal? or what do you think will be at fault considering I have changed the sensors and relays?

Thank you

[rwb]

80 sounds about right on a 1.9, and anything over 90 sounds wrong.
Have you had a new thermostat at all?

[crackpotterpig]

the gauge isnt always 100% accurate as long as you arent getting any air locks or severe overheating issues (coolant boiling in system) then i would use the gauge more as a guide.

[jonsowman]

The thermostat was stuck open on mine. Sat at about 70C on motorways and went up to 90 in traffic.

New 83 degC stat, now it stays there all the time

[fuvureju]

Thanks

yes it is most likely the thermostat...that makes complete sense and i expect t find it failed open!
I have never changed it so it is over 16 years old!
Off first thing tomorrow to buy one!

thanks

can't think why I just did not think of it!

[fuvureju]

well i have replaced the thermostat

interestingly when i test the old one in water which i boil then place in cold water the thermostat seems to open and close without issue (though I am not sure at what temp it is doing so exactly
however, yet to give the new one a road test as in trying to drain the coolant i broke the radiator plug so it is still in there but not sealing properly with a slow drip leak and still trying to work out how to get the old one out and then find a replacement for a new one as there does not seem to be a part number for it

[fuvureju]

Well,

i have found that the old thermostat was not closing completely...a very small gap but enough to enable the water to flow around.
Anyway, I took the car for a good run today after having refilled the coolant system yesterday. I am confident there are no air-blocks in it and was properly bled.
Well today it seems to be running around 87 degrees (previously when all was working properly for the first 12 years or so, I noted 80 degrees was typical).
Then at one point whilst in slow traffic due to an accident, during a blizzard with an OAT of minus 2, the temp rose rather concerningly to 99-100 degrees, at which point i put the heater on full and it dropped to 95 degrees. Subsequently it then settled down at 87 degrees.

So the question is what seems to be going wrong intermittently to allow the coolant to reach such a temporature
I have replaced all the fan relays 2-3 years ago and also the coolant thermistor, the bitron and gauge temp sender 2-3 years ago as well.
I have two thoughts - fans (but see above re relays and temp sensors) or a faulty/intermittent water pump.

As I say I have replaced the relays and sensors recently, but the use of the heater seemed to prevent further overheating and enabled it to cool to 95 degrees whilst stuck in traffic. IS there a chance the circuitry is faulty..how should i check this?

Or could ti be a faulty water pump which is stopping intermittently?

Id appreciate anyone's thoughts...

[rwb]

Well, two steps forward at least

whilst in slow traffic due to an accident, during a blizzard with an OAT of minus 2, the temp rose rather concerningly to 99-100 degrees

That's definitely wrong.

So the remaining question is: do the fan(s) work? (Do you have two fans? I have one.)
Are they seized? Easy enough to check. (I didn't )

All I can think of is to get it warmed up and sit with the engine at 3,000 rpm and with the air con on until the temperature gets over 90, then see what the fan is up to. (This is on my to-do list, but I'm waiting until it's a bit warmer )

[fuvureju]

Hi thanks for that
sorry i forgot to say that the fans do seem to spin certainly at slow speed and do their slow cycle. Also if i disconnect the Bitron switch then the fans come on at high speed but
I've not been able to get it above 90 degrees (when not driving) long enough for me to be able to check if they then switch on.

It clearly is an intermittent problem as i see a rise for 5-10 mins then the temp seems to recover. I need to check the fan relays again fir sure.

I cant find any record of the water pump being changed (I have had the car since new and done all 135k miles on it so i know it well) and was wonderign whter this can be intermittently faulty? Is it worth replacing? I only had the timing belt done 5 years ago and 15k miles ago. (I am currently doing low mileage due to work reasons)

But i cannot understand why it now seems to run at a steady 87 rather than the steady 80 i was used to seeing?

any thoughts greatly appreciated!

thanks

[rwb]

OK, so the fans work.

So the problem is that the fans not activating when the coolant temperature is high?

[jasper5]

Hi thanks for that
sorry i forgot to say that the fans do seem to spin certainly at slow speed and do their slow cycle. Also if i disconnect the Bitron switch then the fans come on at high speed but
I've not been able to get it above 90 degrees (when not driving) long enough for me to be able to check if they then switch on.

It clearly is an intermittent problem as i see a rise for 5-10 mins then the temp seems to recover. I need to check the fan relays again fir sure.

I cant find any record of the water pump being changed (I have had the car since new and done all 135k miles on it so i know it well) and was wonderign whter this can be intermittently faulty? Is it worth replacing? I only had the timing belt done 5 years ago and 15k miles ago. (I am currently doing low mileage due to work reasons)

But i cannot understand why it now seems to run at a steady 87 rather than the steady 80 i was used to seeing?

any thoughts greatly appreciated!

thanks

Did you check the temperature rating of the new thermostat?

It's possible you have fitted an 88 or 90 degree stat where the old one might have been 82.....this would explain running at 87 degrees.

[fuvureju]

Hi thanks for these pointers

yes i even went to the extra expense and bought the thermostat part from Peugeot dealer direct with their official part number and it was stamped with 83 deg.

I guess i need to check poss just do a precautionary replacement of all 3 relays.

My other thought is if it is not fan related, can the water pump stop intermittently...
whatever is the cause it seems to be fine for 90% of the time but then occasionally something stops and the cooling does not occur... and i am wondering if the relays are fine, then can it be the water pump stopping to function.turn occasionally...as i say i don't think this has ever been replaced from new!

thanks for all your continued thoughts

[madmadmax]

has the coolant be changed at the right service intervals, if its not it could be a build up of scale and rust in the coolant system and be partly blocking the system sum where

[fuvureju]

Now there's a thought

apart from a general flush what else can I do...is there a cleaning solution i can run through the system?

[madmadmax]

back flush or replacement of parts