Diesel thermostat definative answer - Page 120

HarryM1BYT · 21st December 2011, 10:02

Quote:

Originally Posted by RichB

I've tried two of the renault inline stats in my top hose, one was rated at 88DEGC and the latest one rated at 89DEGC. However, I only ever see 83-85DEGC on the OBD temperature display when cruising at 70mph on the motorway.

It feels plenty warm enough from the heater and it warms up pretty quickly, but I'm wondering why I'm not seeing a few Deg higher? Could it be the dash reading?

Rich

It could well be the dash reading (temperature sensor issue), but I would suggest setting the heating to cold first, just to make sure you aren't holding the tengine temperature down by taking heat from the system via the heater.

RichB · 21st December 2011, 10:04

It's been like this summer and winter, with heater on or off. So it sounds like the stat is doing it's job. Just curious if it is actually 83-85 DEG or if it's a low reading form the sensor.

Rich

HarryM1BYT · 21st December 2011, 10:47

Quote:

Originally Posted by RichB

It's been like this summer and winter, with heater on or off. So it sounds like the stat is doing it's job. Just curious if it is actually 83-85 DEG or if it's a low reading form the sensor.

Rich

Any way that you could measure the temperature independently of the sensor - IR temperature gun or similar?

malcolm e boo · 21st December 2011, 16:36

I have had my thermostat replaced today with a new OEM one.

I have retained the old one.

If it is of any use to anybody who wants to explore why it failed(Engine temp never got up) then let me know and I will send it out to you.

HarryM1BYT · 21st December 2011, 17:06

Quote:

Originally Posted by malcolm e boo

I have had my thermostat replaced today with a new OEM one.

I have retained the old one.

If it is of any use to anybody who wants to explore why it failed(Engine temp never got up) then let me know and I will send it out to you.

I had intended to (but forgot) retain my old OEM stat last year when I had it changed. My intension was to see if I could work out how they were failing.

I would like this, but I'm sure there will be more capable forum members who could maybe make better use of it, so for now I'll wait.

Shabbs · 21st December 2011, 17:18

Incidentally, over the years my engine has indeed taken noticeably longer to warm up and last year was luke warm during the best part of the winter. This year it seems better but not as good as it originally was. Roll on my top hose stat.

diplo-matt · 21st December 2011, 18:10

Quote:

No one has been able to determine why they do fail, but fail they do. It is not a complete failure, rather that they develop an habit of opening earlier and earlier in temperature - which I agree is a rather strange failure mode for a waxstat.

Stats fail on many different kinds of cars, ive had a fair few that have suffered from a knackered stat. On these i suspect the spring gets weak and the stat opens too soon, dont they have a small amount of mercury in them to push against the spring?

Im not totally familiar withe workings of the bmw stat, but my TDCI warms up no slower than my mates Octavia, diesel engines as a rule dont end to warm up as much as petrol.

I can't believe so much technical rubbish has been written about what is clearly a case of a knackered thermostat.

HarryM1BYT · 21st December 2011, 19:12

Quote:

Originally Posted by diplo-matt

Stats fail on many different kinds of cars, ive had a fair few that have suffered from a knackered stat. On these i suspect the spring gets weak and the stat opens too soon, dont they have a small amount of mercury in them to push against the spring?

They use a wax cartridge, with the wax's formulation calibrated to melt at a set temperature. As it melts, it expands and the stat opens. The spring closes the stat, againt the pressure of the wax. If the wax leaks out, the stat fails safely open - which was the big selling point of wax stats in the 1960's.

The spring makes no difference to the opening point, it only has to put enough pressure on the valve to close it. No one has come across one of these failed stats with a weaked spring, or one failing to close.

diplo-matt · 21st December 2011, 19:22

Quote:

The spring makes no difference to the opening point, it only has to put enough pressure on the valve to close it. No one has come across one of these failed stats with a weaked spring.

Thanks for that, i couldnt quite remember how they fully worked in terms of opening and closing.

Mike Noc · 21st December 2011, 23:11

Changed my thermostat yesterday, not that it had failed but the housing was leaking. Interestingly the closing spring did feel weaker on the old one, and with the new one the engine does heat up a little bit quicker.

Original had done 304k miles so got my money's worth.

Mike

21st December 2011, 10:04	#1192
RichB Gets stuck in ZT260 SE, ZT-T+ CDTi Join Date: Aug 2009 Location: Staffs Posts: 583 Thanks: 13 Thanked 16 Times in 13 Posts	It's been like this summer and winter, with heater on or off. So it sounds like the stat is doing it's job. Just curious if it is actually 83-85 DEG or if it's a low reading form the sensor. Rich __________________ 53 MG ZT 260 SE Monogram Garnet Red #073 61 Seat Exeo ST TDI Daily Driver 99 Mazda MX-5 Turbo tracktoy

21st December 2011, 17:18	#1196
Shabbs Loves to post Rover 75 Contemporary SE, Starlight Silver Join Date: May 2008 Location: North of Engerland Posts: 497 Thanks: 14 Thanked 16 Times in 15 Posts	Incidentally, over the years my engine has indeed taken noticeably longer to warm up and last year was luke warm during the best part of the winter. This year it seems better but not as good as it originally was. Roll on my top hose stat. __________________ [SIGPIC][/SIGPIC]--------------------------------- 2005 Contemporary SE CDTi The Right Colour - Starlight Silver Member No: 3872 ---------------------------------

21st December 2011, 16:36	#1194
malcolm e boo Regular poster ZT Join Date: Nov 2011 Location: North West Posts: 55 Thanks: 0 Thanked 0 Times in 0 Posts	I have had my thermostat replaced today with a new OEM one. I have retained the old one. If it is of any use to anybody who wants to explore why it failed(Engine temp never got up) then let me know and I will send it out to you.

21st December 2011, 23:11	#1200
Mike Noc This is my second home Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009 Location: Hampshire Posts: 11,579 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	Changed my thermostat yesterday, not that it had failed but the housing was leaking. Interestingly the closing spring did feel weaker on the old one, and with the new one the engine does heat up a little bit quicker. Original had done 304k miles so got my money's worth. Mike