Had 2 new thermostats in the 200tdi. Ran it without one in and it went fine, although it ran cool on the gauge. Put a new gauge and sender in and tried a new thermostat, gauge reads high but the coolant in the tank is lukewarm. Bottom hose is fairly hot and the top hose is Luke warm. Any ideas on what the problem is?
Cheers

200 literally takes an age to warm up at slow speed.
Waxstat is the best but now hard to get hold of, was it a proper 200 stat with the bypass shut off bit?

Problem with the gauge/sender is you dont know whos messed with it in the past

lynall said:

200 literally takes an age to warm up at slow speed.
Waxstat is the best but now hard to get hold of, was it a proper 200 stat with the bypass shut off bit?

Problem with the gauge/sender is you dont know whos messed with it in the past

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Fitted one from Steve parkers

Its the right type of stat but its the blue box thats going to be your main issue, Ive tried a couple of britpart ones and they are just utter shti, one didnt even open at all and the engine had never ran so hot! that stat went in the bin asap.

A rough rule of thumb is of its anything important dont use britpart, things like lights/wipers/mudflaps etc just fine.

Might be worth seeing what a Bearmach one is like.

"things like lights/wipers/mudflaps etc just fine"

When browsing for engine spares recently I noticed that one supplier lists a few Britpart items as "OEM". This includes important stuff like oil seals.

Some britpart items are sourced by britpart from OEM manufacturers.

lynall said:

Its the right type of stat but its the blue box thats going to be your main issue, Ive tried a couple of britpart ones and they are just utter shti, one didnt even open at all and the engine had never ran so hot! that stat went in the bin asap.

A rough rule of thumb is of its anything important dont use britpart, things like lights/wipers/mudflaps etc just fine.

Might be worth seeing what a Bearmach one is like.

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I’ve managed to get hold of a waxstat. Will try it and let you know! Cheers

From your description of luke warm top hose /header tank it doesn't sound like you actually have a "coolant issue" or thermostat issue, more like the gauge / sender pairing isn't quite right. When you say it reads high do you mean in the red or just high up in the white? Ideally you need to stick a thermometer in your header tank and take a coolant reading.

moth said:

"things like lights/wipers/mudflaps etc just fine"

When browsing for engine spares recently I noticed that one supplier lists a few Britpart items as "OEM". This includes important stuff like oil seals.

View attachment 140082

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If the Britpart number has a G on the end its likely to be okay, G = genuine

Over the years Ive used plenty of their parts and most need some form of tweaking or are just plain carp, no issues with the G part numbers but then they are twice the price so dont expect any.

For oil seals use Corteco Island 4x4 list them.

Ps and no way would I fit a Britpart rear main seal! even though the one in your pic looks like the real deal, its a massive job if it fails.

The only way to be sure about engine temperature is to fit a more accurate gauge (Durite etc) - there are plenty on the market, and are pretty much a straight swap if the threads on the sender unit are the same. I ended up with 5 duff thermostats (including a Waxstat one) before finding one that opened at the right temperature. Ironically this came from Eurocarparts.

Just been pondering all this again myself. My head gasket change seems to have made my engine temperature a tad low so maybe that gasket was doing naughty things other than blowing gasses at the bulkhead.
So some thoughts that might or might not be relevant to your case:
1. Temperature sender and gauge must be a suitably matched pair. Mine is in series IIA and the standard 200 TDi sender is unmatched so uses the 2.5 petrol adapter so the thermostat housing accepts the series sender. I make sure the electrical path through the adapter to the head is not give additional resistance by rust or scale buildup on the various bits.
2. To doubly monitor the temperature I fitted a kitchen type oven thermometer with a nice stainless probe on the end of a braided, temperature-resilient lead. I cut a big BSP thread down one of those round cast bosses on the top half of the housing then used a series of reducing bushes ending with a fitting that just pinches a small o-ring around the probe to seal it. They are good for high temperature use and have the benefit of an alarm if your preset temp is exceeded. It is a bit naff in that it's AAA powered and loses the setting when turned it off but it's handy to fire up when concern arises. Some of them come with a lead that's a tad too short to reach somewhere nice in the cab.
3. My thermostat housing had not been gripping the thermostat. I wondered if there should be something to grip the thermostat. The thermostat danced about in there and wore an annular groove on the upper half of the housing. I don't know how much unwanted cooling is caused by this. I dressed the top half of the housing back a bit with wet'n'dry on a very flat mirror backing to reduce the wear depth.

Stat should have a rubber washer type thing fitted to the outside of it to keep it still
https://www.lrdirect.com/ERR2803-Thermostat-200Tdi/

Kev12 said:

Stat should have a rubber washer type thing fitted to the outside of it to keep it still
https://www.lrdirect.com/ERR2803-Thermostat-200Tdi/

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I could be wrong but I think the rubber seal/washer thing is for the 300tdi engine?

Yeah my 200tdi doesn’t have a rubber washer :/