405 GLD 92 Temp gauge

[stan108]

Hi My temp gauge moves to the next mark above the mid when travelling at 70 mph on the motorway. On slowing it comes back to the mid mark. Is this normal ? Previously it would stay at the mid mark.
I have used steel seal and it has stopped the pressure on the expansion tank and loss of coolant, Also I have replaced the thermostat. There may still be some air in the system though. tia

[oldpug]

How old is the radiator? if its old and dirty inside the coolant will not flow fast enough to cool the block at speed.

[stan108]

Thanks oldpug. It was replaced about 2 years ago. It looks in good condition from the outside and I flushed it last weekend with a hose pipe, the water came out quite clean.

[stan108]

I put some Holts Speedflush in the rad last weekend, instructions said to drive 20-30 miles, it started to seriously overheat before I had done 2 miles,just managed to get back home, after having to stop to let it cool down severadl times.
Flushed the rad again and filled with water, took it for another drive and same problem. Again flushed the rad, filled up again with water and antifreeze. This time it seems to be OK. Temp gauge stays consistantly below mid and only went slightly above mid point when I took it up a long steep hilll, but came back down agian as I reached the level.
So thanks to oldpug again for the advice.

[Donaldiesel]

You seem to have done all the right things to get it sorted, so just some comments on cooling.

This is the XUDiesel engine. It is important to bleed out all the air when refilling with coolant. Otherwise you can get localised hot spots and possible damage to the head. The bleedscrew positions are shown in your handbook. Airlocks also mean that the car heater will not work properly.

Your use of steel seal may have blocked small coolant passages in the engine, hence the need for much flushing. Now you have got it working ok, it is normal for the coolant temp to vary with the load, as long as it doesn't overheat. The fans should cut in when it rises above normal and quickly bring the temp back down, so worth checking these. Antifreeze mix has more efficient heat transfer than plain water so helps with cooling. Never use the car without antifreeze - iron block with alloy head needs a constant corrosion inhibitor.

The system will pressurise as it gets hot, but not excessively so or such that it lifts the expansion bottle cap. No pressure means coolant leak or faulty cap, excessive pressure means combustion gas leak into the coolant. Most garages have equipment to quickly test this.

[stan108]

Donalddiesel ,Thanks for that . As it happens the temp still creeps up at 70 mph, but does not at any other time, in traffic etc , the heater works very efficiently.

I was wondering if the steelseal had created some blockages. The only bleed screw I could find was on the radiator, the Haynes manual says there are 2 more but I could not find them.
Thanks again for your advice.

[Donaldiesel]

There should be bleed screws in the hose to the heater and in the thermostat housing. There are some variations in the later versions of the XUD engine and they may be hidden by other engine parts. What type of antifreeze are you using?

A correction to my earlier post:
Antifreeze has less efficient heat transfer than plain water. The engine will tend to heat up quicker when antifreeze is added, and the fans may come on more often. Don't be tempted to use plain water to improve the cooling though - the resulting corrosion products will in time cause blockages and overheating. The thermostat and fans should keep the engine at the optimum running temp. There is a product called 'water wetter' which improves the thermal transfer properties of the coolant, but a Pug diesel in good order should not need it. Note that some of the latest antifreeze products are not suitable for older engines as they can damage seals. Stick with standard ethylene glycol or low toxic propylene glycol (if you can get it), and make sure all air is bled from the system.

Regards,
Donaldiesel

[stan108]

Hi Donalddiesel,
I have searched high and low for other the bleed screws. Certainly none on the thermostat housing I will have another search on the heater hose.
I am using the standard ethyl glycol blue antifreeze.
Thanks again for the advice.
Regards

[Donaldiesel]

On the thermostat housing they are usually two brass allen key type screws (socket cap head screws). However, since your model has a bleed screw on the radiator, this may be instead of the thermostat housing ones. However, there should be one on the highest point of the heater hose - either a brass socket cap screw, or a black plastic thumb screw. If not, it would be a good idea to fit one.

You haven't said if your car is turbo or non turbo. On turbo models you may have to remove the intercooler from the top of the engine to find the bleed screws.

Regards,
Donaldiesel

[stan108]

Hi Donalddiesel
I will do a thorough search on the heater hose. On another Peugeot site, a poster with a 405 also said he could not find any other bleed points apart from on the radiator.

If I were to fit one on the heater hose, is this something that scews into the rubber ?

Mine is non turbo.
Thanks again

Regards

[Donaldiesel]

On XUD engines I have worked on there is always air trapped in the heater hose to the water pump return manifold when refilling the coolant. I don't see how the heater can work effectively unless this is bled out. If Peugeot did not fit a bleed screw on your model, there must be a reason, so perhaps worth asking the tech guys at your local Peugeot main dealer. Maybe the pipe runs have been rearranged so that there is no longer a high spot to trap air.
Regards,
Donaldiesel

[stan108]

Hi Donalddiesel it's a mystery - I have just had another search, and there is definitely no bleed screw on the heater hose or on the bulkhead where it goes in. Also none on the thermostat housing as I have had this apart to replace the thermostat. Your last point - "Maybe the pipe runs have been rearranged so that there is no longer a high spot to trap air." -
- the heater hose is no higher than the bleed screw on the radiator.
Thanks again
Regards