Diesel thermostat definative answer

[Starman]

Well a bit warmer today and I had to do a quick run to Telford as Jude was taken I'll on the way to work and was too poorly to get back home.
So with some "progressive" driving I got a top temp, (albeit fleeting), of 96C before tumbeling down to 87C, and an average of 88C.
I wasn't too sure if it would have gone higher as I had reached a fast enough speed and was backing off the gas. So whether the stat opened or the drop in engine load resulted in the drop in temp.
No loss of water and the level is still above the fins in the header tank!

FBH off, QTH 107, Ambient temp 5.5C, 40 mile round trip and a light Cajun chicken salad for lunch!

So looking good so far.

Regards. Steve.

[Jules]

HI Steve
That's what worries me, when I carried out some road tests (but ran out of road)
The test car went to 100 C and was still climbing but I had to back off.

The new Stat would be fully open at that point and to see the temp still rising is not a good sign to me (insufficient flow for max engine load with the smaller stat orifice)

[Tony K]

After reading this monster thread, I've gone with the 'Renault up the pipe option' @ £7 from a local motor factors. I have seen a temperature range of 84-87c (outside 6c) on a mix of round town and spirited dual carriageway. Seeing as my test runs before the fitting showed a max of 72c, I'm happy with the results until I get the OEM thermostat changed. Be interesting to see if it improves after bleeding.

One issue has popped up, I think the coolant tank cap is weeping, I've found antifreeze on the tank and spots on the boost pipe. I've ordered a new cap and a top rad hose as a precaution as these are the only things I've touched.

[Starman]

Originally Posted by Jules

HI Steve
That's what worries me, when I carried out some road tests (but ran out of road)
The test car went to 100 C and was still climbing but I had to back off.

The new Stat would be fully open at that point and to see the temp still rising is not a good sign to me (insufficient flow for max engine load with the smaller stat orifice)

Hi Jules.
One train of thought, is will the OEM stat, (when working as should), allow the engine to increase to temperatures around the upper 90's/ lower 100's during moments of high load/ work?
I must admit that at the moments of seeing the higher 90's, I was hard on the gas moving away from roundabouts on a dual carrigeway..
Normal cruising on the way home I was seeing 92C max and then a tumble back to 87C, which seemed almost uncannily too textbook for the QTH107 seeing as where its placed!
But in saying that, I agree with you on this, 3C increase in ambient temp has seen a 3C increase on engine temp! And I know you know your onions... so if you say caution.... then caution it is..!!

Regards..me

[gefary]

As the system is pressurised it should be able to go over 100C without boiling.
A pressure cooker blows above 115C.

Who wants to put that theory into practice

[wuzerk]

Originally Posted by gefary

As the system is pressurised it should be able to go over 100C without boiling.
A pressure cooker blows above 115C.

Who wants to put that theory into practice

From what I have read so far those using the 'in-pipe' thermostats might not be able to avoid putting it into practice! I believe that the 50-50 mix of antifreeze also raises the boiling point so it will certainly not boil at 100C.

[T-Cut]

Originally Posted by gefary

As the system is pressurised it should be able to go over 100C without boiling. A pressure cooker blows above 115C.

115C is regarded as the upper end of normal operating temperature. At 116C, the temperature gauge starts to rise (rather quickly is some cases). The red end of the gauge is around 120C according to the MGR literature. At normal atmospheric pressure, the standard coolant will boil at 107-108C, but it will actually start to boil in the engine at around 118C when the system is fitted with the standard '140' pressure cap. This is why with a good cap, the coolant will be discharged when/if the temperature gauge goes towards the red zone. So, if everything is working as it should, no coolant will be lost providing the engine temperature doesn't exceed 117C (approx).

TC

[Thomas]

Gents just to add my two pence worth again, even with the QTH107 stat in my car it still takes quite some time to heat up,even with heater off. the stat was tested before fitting and appeared to be operating correctly, I read a post that said car was showing 90C within 4 miles was that with a FBH running also? (seems awfully fast to get to 90C for me) now my own car will reach 90C no bother and right up to 100C before cooling fan kicks in but that is if I actually sit and rev it for a while until it reaches those temperatures, once it is up there even driving with the climate set to auto ie at 23C so fan running as it should it stays at approx 88C however it seems to be getting it up to those temperatures which is my problem,

[Jules]

Originally Posted by gefary

As the system is pressurised it should be able to go over 100C without boiling.
A pressure cooker blows above 115C.

Who wants to put that theory into practice

Yes I fully appreciate pressure verses higher boiling points etc but I would prefer not to see 100C PLUS when in top gear with full airflow AND the darn cooling fan running ............rather defeats the object of trying to raise your MPG

[Thomas]

Originally Posted by Jules

Yes I fully appreciate pressure verses higher boiling points etc but I would prefer not to see 100C PLUS when in top gear with full airflow AND the darn cooling fan running ............rather defeats the object of trying to raise your MPG

got to agree with Jules here first time I saw my temp that high I was frightened as it was minus figures outside!