Couple of theories on the diesel cool running problem?

[daznkel]

Originally Posted by T-Cut

Found what I was thinking about. The photo is in the link quoted in the first post of this thread.



The nick in the annulus looks like removal damage. It just stuck in my mind.

TC

It is indeed removal damage! I had quite a struggle to remove the stat to say the least! The damage was caused by prising it out with an old screwdriver!

[T-Cut]

Originally Posted by daznkel

It is indeed removal damage! I had quite a struggle to remove the stat to say the least! The damage was caused by prising it out with an old screwdriver!

Thanks for confirming it - and the photos.

TC

[Kennyeth]

Originally Posted by clf

I am starting a new thread as I didnt want to hijack Daznkel's thread any further.

I have been having problems (let's call it an irritant now) since I got the car nearly two years ago (next monday actually ) .

Started reading through the forum that thermostat was a common issue, so it was one of the first things I checked out, sure enough, it would rarely pass 70 degrees.

Installed the R5 top hose 'stat three times in total. I think I damaged the copper bulbs on the first two, as the temperature would barely reach 72 degrees. But the running temperature did improve. the thrid 'stat, allowed the temperature rise to 80 - 82 degrees under normal running (commuting and to and from the shops).

The temperature would take about 5 miles at 40 - 50 mph to reach 75 degrees, and then to the motorway driving between 70-80 mph for four miles, it would rise to 85 under acceleration and settle to 80 when cruising. This pattern sounds fine and natural to me. It is the numbers that I believe are the issue.

The accepted wisdom, is the original thermostat is faulty, with slow opening. That I accept fully and dont doubt. The other contributing factor is that the engine is very thermally efficient. Again I can accept that fully. I have a replacement OEM (3rd gen) thermostat in preparation for fitting when the engine mount needs to be replaced, may as well, when the engine needs moved about. But until then, I dont want to disturb it.

What I cant get my head around is why the temperature doesnt rise enough to open the R5 stat fully. I havent seen the temperature rise more than 90 ever! Even driving up a steep section of motorway to 90 mph! It dropped to 78 and maintained that on the level for 15 miles at 70-75 mph. I havent also seen the temperature drop suddenly suggesting the stat was opened.

Theory one, is it the radiator?

I can appreciate as you drive along at a steady pace, the temperature can fall with the airflow passing through. But it does stays pretty constant. Just lower than I would like it to be. I am wondering, is it possible that the radiator is blocked somehow as in the picture below. Perhaps corrosion building up and blocking the flow in the section tinted gold. Therefore the stat doesnt open fully and the coolant doesnt fill the radiator quickly enough to fill it. That flow passes quickly through, cooling quickly. The radiator if not filled completely, would not have enough ambient coolant heat to keep 'warm' the flowing coolant. Or perhaps, if the radiator contained 2 litres of coolant, but with the blockage I suggest, maybe only 1 litre is passing through. My thinking is that the 1 litre of coolant would cool quicker than 2 litres, therefore colder going into the engine. (latent heat capacity?)



I know it is unlikely, but I am trying to think of other potential issues that can cause it to run at lowish temperatures, even with its thermal efficiency. I know that the radiators are the same throughout the range of engines, so therefore were likely designed to keep the petrol engines cooler. But the standard 'stat was designed to open fully at 88 degrees in the diesel which would suggest to me that the coolant should be capable of reaching 90-95 degrees, and maintain 82-88 even with that radiator.

I have read a few others with the same issue as myself, after fitting the top hose 'stat. Some people say this solves their issue. I have read a couple of times, whilst it increases the temperature, it still doesnt increase the temperature to the magic 88 degrees.

Theory two, is the temperature sender faulty?

well, as the it says, could it be the coolant temperature sender? If the temperature sender becomes faulty, and under reads, the ECU would then overfuel? This would cause the reduction in fuel economy, and possibly even a reduction in power. I think this is a more realistic issue, and only affecting a small number of us ....... so far. The coolant could actually be running to the magic 88 degree region, but the sender is reading 10% low.

I am sorry it is such a long winded post, but wanted to include the background too, to eliminate or suggest alternative issues. I do not drive hard, and with it being an auto, have little control of the revs. But even driving hard, the temperature rises to around 80-82, and then falls to 75 when cruising.

Any thoughts would be appreciated, because it is driving me nuts. I understand how the system works. Coolant effectively starts off cold in the engine, water pump pushing it about, over the sender unit, until it reaches the opening temperature of the 'stat, which gently opens as the temperature rises, softening the wax. Coolant flows into the top hose of the radiator, pump and gravity pushing the coolant to the bottom of the radiator via the tubing cooled by the fins. Out the bottom hose, into the engine and back around, with the stat staying partially opened under normal use, allowing the flow to maintain a steady temperature of coolant. So with the radiator issue I suggested above, being unlikely, that only leaves the sender as the other component in the system that could cause an issue like this.

Where is the sender located, and is it easily accessible? It only occurred to me today, but wont get the chance to look for it 'til the weekend (EDIT: just looked it up on Rimmers, seems to be below the inlet manifold, will this need to be removed to access it?)

Just to add, interior temperature is fine, and the coolant temperature drops slightly when using the the heater.

Alan, I can`t add anything scientific but reading your post and your damage to the first two stats. I imagine that was caused by pushing them home.....
...heres my techy bit on some vacuum cleaners you get a set of tools, I used one of the vacs tool nozzles oposite way round to push the stat to the correct position.
that way you only have contact with the stat`s outer rim, it seemed a perfect fit.
Ken.

[clf]

Well today, I bit the bullet and took out the old stat and fitted the new one. Checked the new one reached temperature in boiling water first before it opened. It seems to open around 86 to 88 degrees. The thermometer I was able to get, coincidentally maxes its display at 88 degrees lol. It is a meat thermometer, and in no way do I claim it is accurate but it does give a rough guide.


First video shows stat closed, but filled to show water leakage.



A longer video shot from the side, to show the draining. It speeds up to 5x at 40 seconds, and returns to normal speed at 40 seconds before the end. Total time to drain was 4 minutes 9 seconds.



next video shows the water level dropping in the old stat, I didnt measure this in its entirety, but am guessing it will be roughly the same as the new one.



Again, the old stat, still inside the hose. This shows from the side the draining. I had to tip it to spill out, but it didnt drain quickly.



This video, the new stat was put into the hot water after the cold water fill/drain test. Lifted out after 5 seconds to see if the stat opened any more than when fully cold.



Last video, the new stat is allowed to rest in the hot water, approximately 95 - 100 degrees (cannot vouch for the accuracy of the thermometer) allowed to open and draining is observed. The stat is open fully, and water drains straight through.




I didnt capture on video, the stat opening at roughly 88 degrees. But I did lift it out of the water when the thermometer reach 88 degrees, from cold.

After fitting, I wanted to test the old stat, but it broke up as I took it out.







The result is not yet conclusive. However, I did let the car idle for a little to check for leaks, and topping up, the lost coolant. I went for a short drive. I didnt use my commuting route, however I did drive normally for roughly the same same distance. I also drove up a steep hill to put the engine under load. Giving a similar effect of joining the motorway. The temperature reached 89 degrees under load. Under normal driving it kept climbing relatively quickly to 86 and settled at around 82. When coasting downhill, it did drop to 79, but rose again to 81 when I drove on level ground for a mile. After my morning and evening commutes tomorrow, I will be able to give a better comparison.

With these very unscientific figures, I can conclude that the sensor is operating correctly. My next course of action, would have been the SC inline aluminium housing, but since it will cost roughly the cost of installation of my already procured OEM stat, I will have that fitted instead. It seems that the inline stat can fail as the OEM one does. It is unfortunate that it didnt last long. But it is easy enough to replace, it could even be seen as part of an annual service, if circumstance didnt allow the fitting of a proper OEM replacement.

Thank you to all who have contributed, with their thoughts and suggestions. Although I wouldnt rule out a sensor problem ever, but as it stands now, I am satisfied they are still reliable even with their age. (I will keep the one I have ordered to hold as a spare part).

[clf]

Originally Posted by Kennyeth

Alan, I can`t add anything scientific but reading your post and your damage to the first two stats. I imagine that was caused by pushing them home.....
...heres my techy bit on some vacuum cleaners you get a set of tools, I used one of the vacs tool nozzles oposite way round to push the stat to the correct position.
that way you only have contact with the stat`s outer rim, it seemed a perfect fit.
Ken.

Thanks for that Kennyeth. I had thought of using one previously, but this time I had a deep socket, that made no contact to the bulb at all , which worked a treat.

[T-Cut]

If I understand the video sequences, the first one indicates that the new stat leaks water when closed, which doesn't bode well I'd say. Clearly, this stat when fitted has improved the running temperature over the old one, but won't get as high as it might due to the pre-opening leakage. Is this stat the rubber seated one or has it a formal bleed vent?

Thanks for doing the tests.

TC

[clf]

Originally Posted by T-Cut

If I understand the video sequences, the first one indicates that the new stat leaks water when closed, which doesn't bode well I'd say. Clearly, this stat when fitted has improved the running temperature over the old one, but won't get as high as it might due to the pre-opening leakage. Is this stat the rubber seated one or has it a formal bleed vent?

Thanks for doing the tests.

TC

It is the new one from the close photographs, but I could not see any kind of seal. It seems to be metal to metal on the disc. What does concern me over the sealing, is that the water pump will be forcing the coolant towards the thermostat into the direction of the disc opening. So the pressure of the coolant alone could open the disc.

There are no bleed vents in either of them.

[T-Cut]

Water is clearly leaking through the valve. The water pimp will obviously increase this throughput. It can't open the valve itself (my measured pump pressure in a 1.8PRT system was 1.5 - 2psi), but a lot more will bleed through than is seen in your demo. The OEM stats have a rubber edged valve/seat, which presumably ensures no bleeding. The rate implied by your tests will be enough to compromise the running temperature. We ideally need to find an inline stat that doesn't bleed when closed.

TC

[clf]

I wonder if the older or alternative version be sealed better, the one without the copper protrusion. I noticed on dmgrs's site, there is a stat for, I think it is a rover 600 of a similar design. Perhaps that would fit? I didn't look for specs on it, assuming it would have been investigated, and used before the Renault 5 one.

[T-Cut]

Blimey, the R5 stat I ordered has just arrived. I've done a simple bleed through test using warm (40C) water and like yours, it leaks. There's no air vent/bleed present. This is a Circoli brand supplied by Car parts for Less (Euro Car Parts) and at £3.99 delivered was the cheapest (and presumably the most used) R5 stat I could find. I guess getting best results from these type of stats will be a matter of pot luck. Some will bleed more than others I guess.

TC