Engine: 70 T5: New thermostat, engine temp still dropping when coasting

[MikeS100]

Originally Posted by 960kg

That is normal!!

If it was a very long stretch like down the M20 hill at Wrotham Hill, Kent it will drop as mine does.

When you have no throttle the ECU cuts off the fuel so therefore you have NO combustion happening to heat up the coolant and so it gets colder and the needle will drop.......Simples.

The same thing happens in Winter with a cold headwind into the radiator the engine coolant system cannot overcome the extreme cold air so it runs cooler and the needle will be lower. If you then turn around and have a cold tail wind the needle will read normal in the middle as the cold wind is now behind you.

Remember old school motors with radiator blinds?

I go down down the A20 version of Wrotham Hill on my way to work, but unfortunately it's not something as simple as that. I seem to have made matters worse as the needle hardly moved on my way to work this morning. I'm now convinced the thermostat has dislodged in the housing so I will attempt to get it all off over the weekend and refit it properly, like I should have done yesterday!

On a side note though, after I had replaced the thermostat on my old car (Mondel TDCi) the needle would stay in the centre even when going down the M20 Wrotham Hill during the winter and fuel flow dropping to zero. The TDCi Mondeo's are notoriously difficult to keep warm so if that can do it I would hope a petrol Volvo would stay warm. If it cannot maintain a normal operating temperature once this is all sorted out I will be disappointed.

[Clan]

Originally Posted by 960kg

That is normal!!

If it was a very long stretch like down the M20 hill at Wrotham Hill, Kent it will drop as mine does.

When you have no throttle the ECU cuts off the fuel so therefore you have NO combustion happening to heat up the coolant and so it gets colder and the needle will drop.......Simples.

The same thing happens in Winter with a cold headwind into the radiator the engine coolant system cannot overcome the extreme cold air so it runs cooler and the needle will be lower. If you then turn around and have a cold tail wind the needle will read normal in the middle as the cold wind is now behind you.

Remember old school motors with radiator blinds?

yes i do , the amazons had them , but if the thermostat is functioning correctly you dont need a radiator blind , unless perhaps it is -30 C or something :-)

[960kg]

Originally Posted by Clan

yes i do , the amazons had them , but if the thermostat is functioning correctly you dont need a radiator blind , unless perhaps it is -30 C or something :-)

I remember in 1967 with my Morris Cooper the heater would not get hot that winter so had to put Turkey Foil across the grille to keep the engine temp. up and be comfortable inside.

The Volvo X40 GDI i had the other year was supplied with a plastic shield which went under the bumper in that gap to keep the cold winter air out.

[Jas16]

I agree, in my diesel avensis the needle never changed, but in the focus diesel it did (all doing the same journey over a year and a half at least) so I will maintain that the temp fluctuations are normal as long as the needle doesn't go above the 3 o clock position and doesnt drop to the bottom.

Sorry don't mean to demean what other people have said, just reporting on my personal experiences over the last 10 years and believing that to be normal using the theory that 960kg gave earlier

[Christerart]

Originally Posted by Clan

yes i do , the amazons had them , but if the thermostat is functioning correctly you dont need a radiator blind , unless perhaps it is -30 C or something :-)

LOL - you guys haven't been driving an old (then new) 1974 International Transtar 4070 - like this one:

http://www.hankstruckpictures.com/pi...tar_lowboy.jpg

in North Dakota in the middle of winter with a 50 mile an hour headwind and 40 below C.

Let's just say that insulated winter boots and double or triple socks wasn't enough to keep my feet from freezing. I finally found a dealer in Minot who had a full wrap around insulated winter front (covered the whole front up to the windshield - not just the radiator like in the picture) and had them put it on.

Cost a fortune but worth it. In those days most trucks were cabovers due to length restrictions - now most are conventionals - and much nicer (and warmer) - like my last one, one like this:

http://www.truckertotrucker.com/listings/186880.cfm

I've been thru winter storms in Minnesota when it was so cold that even with the engine running at full blast the water temp kept dropping to the point the heater wouldn't put out any heat at all. In the end you were just happy it kept running and didn't clog up - because when that happened you were really up the creek without the paddle.

[MikeS100]

Thought I would post an update on this, I had another go at the thermostat today, this time doing it properly and changing the whole housing! I had to reuse the gasket that goes between the housing and the thermostat cover because you can't buy this on it's own, but I put a thin bead of silicone instant gasket on which will hopefully keep it sealed properly. Just took it for a test drive and it's looking good. I let it idle up to temperature first and then the needle stayed steady at the 3 o'clock position for the entire drive, including the same downhill section that it was dropping on before

Coolant level has dropped to the minimum now but I will let it cool down overnight and then top it up in the morning when it's cold. Hopefully that's just becsuse the drive has pushed all the air through so once I fill it up tomorrow fingers crossed it will stay level

It was a bit of a pain to do because you have to take the power steering pump off just so you can get access to the bottom bolt, but having done it now I would say it's not that bad a job really. Hopefully it's something I will never have to do again though as it was still the original one in there so the new one should last a good few years!