308 1.4Vti Several issues

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Dannyboy
Posts: 39
Joined: 10 Jul 2010, 17:24

Re: 308 1.4Vti Several issues

Post by Dannyboy »

Tks for that info Admiral51. If the same strategy is applied to the 1.4Vti engine, if I read it correctly, it allows the temp to go up to 105 deg when the car is moving and when stopped ( idle above 1450 rpm when stopped i don`t understand ? ) the electrical assist to the stat kicks in to cool it more. 105 deg is seriously hot. My coolant is a bit watery at present due to all the messing around , I wonder if it was a strong mix would it handle the temp better ...ie.....not be as close to boiling point. All this time the temp guage stays at 90 deg . Wonder at what temp the overheat warning comes on ? I got up to 108 deg and there was no warnings. It looks like you really need your system to be all working correctly or you can be in an overheat situation very quickly with no clues from your guage . I believe these cars are quite economical on fuel , 40 mpg tipping around ? ...maybe thats how they achieve it . Still think I have an ECU control problem. Even with the stat manually open the fan isn`t kicking in as expected when the temp gets up to 108 deg and when a serviceable stat is fitted it seems to be cycling @ 105 deg. Its like the ECU isn`t getting the temp info even though I`ve tried 3 different sensors and the sensor wiring to the ECU is good. Once at idle , it did operate normally and the temp dropped from 90 a bit and the fan kicked in with the bottom hose and rad hot......but it only did it once....other wise it was cycling from 105 to 95 ( scanner temps ) with fan barely running and instant bubble over if you stopped the engine. ......hope the ECU I`m going to order will cure it .....there`s nothing left to check !.

admiral51
Donor 2019
Posts: 2231
Joined: 24 May 2007, 10:11
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Re: 308 1.4Vti Several issues

Post by admiral51 »

Dannyboy i am no expert and i cannot check anymore as the boy has sold the pug but i will try and explain my understanding of the stat operation and please do not take this as gospel, most on the forum know to take my thinking with a large dose of salt lol
*******Based on the previous post with the info provided by Marc and may not be specific to your thermostat/engine*****

The thermostat itself will open without any ECU input at 105 degrees, that is its default opening so in my view if everything else goes pear shaped the stat will open at 105 degs.
Having looked at the graphs there are various sensors that detect and effect the piloted part of the stat, ie even though the temp is below the 105 default opening of the stat it can be forced to open by sending a signal to melt the wax, in the diagrams in the post it can happen at 89 degrees, by sending the signal to melt the wax you get the extra 16 degrees needed to open the stat.
The bit about 1450 rpm is something that really knocked me sideways.
The thermostat will not open until 105 degs or unless the system decides it needs to be opened due to load etc.
The 3 steps are used to tell the ECU to open the thermostat to start a bleed process, crazy i know but it works, and if the stat will not open by default until 105 deg how else are you going to bleed the system ?
Somewhere in the post it says something about exhaust sensor and the last bit says about the catalytic sensor being involved in the post operation of the cooling fans.
Think the other graph show temp and % to say what speed the cooling fans should be operating at.

Probably i have been no help but i am trying

** EDIT **
As for the 3 steps i did the following
1. Idle for 10 secs
2. Revs held @ 1800-2000 for 10 secs
3. Idle for 10 secs.

After 2-3 mins both top and bottom rad hoses were warm and coolant needed topping up :)

Colin

Dannyboy
Posts: 39
Joined: 10 Jul 2010, 17:24

Re: 308 1.4Vti Several issues

Post by Dannyboy »

Hi Admiral51....tks for input.....your explanation makes sense. Yes, the idle above 1450 rpm bit doesn`t . What about when you are just ticking over in traffic on a hot day ? If engine is not under heavy load or idling it heats up to 105 Deg ? .....thats hot !!. As regards the bleeding , the two bleed ports are one on the heater rad at the bulkhead and the other on the stat body near the temp sensor......both will bleed air out whether the stat is open or not. They work well enough. I was happy I got all the air out. It will be interesting to see how things work when I replace the ECU and refit the new fully functional stat. This will be my fourth time fitting the stat......did it in about an hour and a half the last time. The first time was a pig.....couldn`t get the pipe from the stat body that goes around the back of the engine out of the plastic pipe that goes from the stat to the water pump. That pipe can easily be damaged, you cant get a grip on it to pull it out of the water pump entry. I replaced it with a new one when I was doing the head gasket. I believe garages charge about 350 euro for a stat change and some won`t do it ..i can see why. Its about 150 euro for pipe and stat body and probably 3 hrs , some of it swearing to get it out , possibly breaking the plastic pipe in the process. The only way I got it out the first time was by grabbing the pipe in a channel locks / water pump pliers and twisting it .....no real space to do that either. You can`t see the end that goes into the water pump and have to "feel" it into place and its a tight fit to push in ....push in too far and the stat pipe wont go in enough to fit the retaining clip and you have to pull it out a bit again and can`t get a grip without damaging it.
Since I got the car you notice other ones.......quite a few 2008 308`s knocking about, the odd 2011/2012 not many 2009 / 2010 ones around. Must be reliable enough when sorted. They don`t sell well and the prices are low......quite a few on local sales sites ...not shifting. Will let you know how I get on.....ECU has to fix it .....there is nothing left !! There was a time when a stat change was a simple job and you could leave it out and blank the rad for the winter if you were stuck with the mechanical fan spinning away merrily. Or what about thermosyphon on the 30`s models.....not even a water pump !.

gwest
Donor 2020
Posts: 30
Joined: 27 Apr 2020, 08:07

Re: 308 1.4Vti Several issues

Post by gwest »

Dannyboy,
When I was warming up my engine after putting in fresh water to dilute any coolant left in the system, if I switched on the A/C the fan came on well before the engine had reached operating temperature. In fact I then turned it off because I thought it would prolong the warm up. At least it confirms that the fan operates.
As far as I can ascertain, having a cooling system pressurised to 15 psi will raise the boiling point of water by 25C. So I am hoping that I will not run into any boiling problems when I first take my car for a proper run using just fresh water in the engine. 50% ethylene glycol only raises the boiling point another 6C.
One consistent problem with your car has been coolant bubbling and spilling over in the expansion tank even though there has been no apparent indication of the engine running hot. I would be really interested to see how much pressure your system was running at, and whether a new cap would make a difference.