Diesel thermostat definative answer - Page 81

Martin75 · 11th January 2011, 21:11

Quote:

Originally Posted by 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) ...

Thomas that was me. I rung my friend who fitted it for me, and he left the car running for over 20 mins, before I set off, so it must have been warm, when I commenced my short (4 miles) trip, prior to checking the temp.

So some distortion here, as against setting off from cold. I'll check the reading again soon and re-post.

Incidentally I don't have an FBH.

T-Cut · 11th January 2011, 22:03

Quote:

Originally Posted by Jules

I would prefer not to see 100C PLUS when in top gear with full airflow AND the darn cooling fan running.

Maybe the flow rate through the wide open stat is too low (valve bore)? I think another issue that could be relevant is whether there's too much pressure drop between the water pump and the inline thermostat. If the 'distance' is significantly greater than the original's position, there will be less pumping efficiency through the stat, especially since the original is still in position. In other words additional flow restriction is present. I think the radiator has ample heat exchange capacity, but the speed coolant passes through it is also important. The results seem to be widely variable, so maybe one stat is preferable to another even though they're of similar setting.

TC

Thomas · 11th January 2011, 22:13

Quote:

Originally Posted by Martin75

Thomas that was me. I rung my friend who fitted it for me, and he left the car running for over 20 mins, before I set off, so it must have been warm, when I commenced my short (4 miles) trip, prior to checking the temp.

So some distortion here, as against setting off from cold. I'll check the reading again soon and re-post.

Incidentally I don't have an FBH.

Ah Martin thanks for that! that would explain things a bit better as I was a bit concerened that your car was heating up way too quick! it will be interesting to see how you get on from stone cold without a FBH so yours in theory should be similar to mine!

rossocorsa · 12th January 2011, 07:08

my car still takes about 12 miles/20mins to reach the 90s and that's with a fbh steady drive of between 30 to 60mph small amount of standing traffic but mostly moving. still have odd fbh behaviour though fan running when I stop and I've disconnected the k bus now.

I don't think 100 under heavy load is too worrying a k series runs at about 95 to 105 all the time

T-Cut · 12th January 2011, 10:56

Quote:

Originally Posted by rossocorsa

I don't think 100 under heavy load is too worrying a k series runs at about 95 to 105 all the time

I agree, the diesel should really run within the same temperature band as the petrols for best results. I guess that's a little frightening at first, but I'm sure many diesel owners will get there eventually and gain the benefits.

TC

rossocorsa · 12th January 2011, 14:19

slightly odd behaviour today got stuck in a queue for 35 mins gauge stayed resolutely just below centre mark as you'd expect scangauge readings though were odd car was showing about 88 when driving but with engine at idle dropped to 83ish in the queue but as soon as I passed the obstruction (after about 35 mins) the temperature rose quickly all the way up to 100 before stabilising and dropping back down to around 88 to 90 seems a bit strange

HarryM1BYT · 12th January 2011, 16:01

Quote:

Originally Posted by rossocorsa

slightly odd behaviour today got stuck in a queue for 35 mins gauge stayed resolutely just below centre mark as you'd expect scangauge readings though were odd car was showing about 88 when driving but with engine at idle dropped to 83ish in the queue but as soon as I passed the obstruction (after about 35 mins) the temperature rose quickly all the way up to 100 before stabilising and dropping back down to around 88 to 90 seems a bit strange

Probably not that odd, I had a new OEM stat fitted a while back and I got exactly the same effect. I suspect it must be the heater matrix dumping all of the engines surplus heat into the cabin. Once you start to move, it will take a while for the stat to reopen, then it will oscillate between over cooling/ over heating, before settling to a steady opening, once the water temperature has mixed well..

Number 6 · 12th January 2011, 18:24

Quote:

Originally Posted by HarryM1BYT

Probably not that odd, I had a new OEM stat fitted a while back and I got exactly the same effect. I suspect it must be the heater matrix dumping all of the engines surplus heat into the cabin. Once you start to move, it will take a while for the stat to reopen, then it will oscillate between over cooling/ over heating, before settling to a steady opening, once the water temperature has mixed well..

COLVERT · 12th January 2011, 20:04

Quote:

Originally Posted by T-Cut

Maybe the flow rate through the wide open stat is too low (valve bore)? I think another issue that could be relevant is whether there's too much pressure drop between the water pump and the inline thermostat. If the 'distance' is significantly greater than the original's position, there will be less pumping efficiency through the stat, especially since the original is still in position. In other words additional flow restriction is present. I think the radiator has ample heat exchange capacity, but the speed coolant passes through it is also important. The results seem to be widely variable, so maybe one stat is preferable to another even though they're of similar setting.

TC

I think that with a flow restriction caused by a smaller pipe or thermostat hole the water flow just speeds up and then slows down again once past the restriction. ( The pressure through the narrow part decreases as the flow increases.) The volume passing through remains constant.

Colvert. ( venturi effect. )

rossocorsa · 13th January 2011, 11:58

had the opportunity to get my foot down today have to say temp fluctuations appears (but may not actually be?) alarming 84 up to as much as 104 (!!!) up and down in a cycle actual gauge stayed firmly just below the centre mark never even quivered. bit worried about cooling/heating cycles though

12th January 2011, 07:08	#804
rossocorsa Posted a thing or two None Join Date: Feb 2010 Location: GRIMSBY Posts: 1,243 Thanks: 0 Thanked 1 Time in 1 Post	my car still takes about 12 miles/20mins to reach the 90s and that's with a fbh steady drive of between 30 to 60mph small amount of standing traffic but mostly moving. still have odd fbh behaviour though fan running when I stop and I've disconnected the k bus now. I don't think 100 under heavy load is too worrying a k series runs at about 95 to 105 all the time

12th January 2011, 14:19	#806
rossocorsa Posted a thing or two None Join Date: Feb 2010 Location: GRIMSBY Posts: 1,243 Thanks: 0 Thanked 1 Time in 1 Post	slightly odd behaviour today got stuck in a queue for 35 mins gauge stayed resolutely just below centre mark as you'd expect scangauge readings though were odd car was showing about 88 when driving but with engine at idle dropped to 83ish in the queue but as soon as I passed the obstruction (after about 35 mins) the temperature rose quickly all the way up to 100 before stabilising and dropping back down to around 88 to 90 seems a bit strange

13th January 2011, 11:58	#810
rossocorsa Posted a thing or two None Join Date: Feb 2010 Location: GRIMSBY Posts: 1,243 Thanks: 0 Thanked 1 Time in 1 Post	had the opportunity to get my foot down today have to say temp fluctuations appears (but may not actually be?) alarming 84 up to as much as 104 (!!!) up and down in a cycle actual gauge stayed firmly just below the centre mark never even quivered. bit worried about cooling/heating cycles though