Technical Broken thermostat - Is it difficult to change?

[BrianMcL]

That's the new thermostat fitted at long last. The problem was indeed additional mounting bolts holding the heat exchanger in place. One's a 13mm head and the other's a 6hex.
They are mounted to the back of the engine block and are most easily accessed by removing the EGR which is connected to the heat exchanger. They're to the right of the EGR and if you hold a small mirror round behind the back of the heat exchanger you should be able to find them.
With the EGR out and these two bolts undone the two bolts holding the thermostat can be undone. The top one's a 13mm bolt and easy enough. The bottom one had me stumped for ages but with the 10mm nut that holds the heat exchanger on the same bolt that holds the thermostat in place undone (and all of the connecting pipes undone, battery and box out, etc as well of course) you should be able to slip a 13mm socket spanner over the end and undo it. It will then come out and the new one can be fitted.

I can't make my mind up whether undoing the metal clamps that connect the metal pipes to the heat exchanger should be undone but if you do undo them watch for the small shims that are inside. Very easy to drop inside the engine.

 

[s130]

Great news Brian.

I'm not sure if I'll be having to follow you down this route. During last winter and the colder morning we are now seeing my Croma takes time to heat up. If I get a good free power drive then the temperature guage gets up to normal (dead vertical) OK. In hot temps 36 deg C and towing the needle still does not move passed vertical.

However on the cold mornings then the guage will climb slowly to one division below normal. (1st double bars to left of vertical). It will then climb and fall between the one div below and vertical position under light engine load and overrun/deceleration. However drive at any speed with moderate load then the temp stay rock solid at the norm position.

I keep on meaning to do some runs with MultiECUScan connected to see a graph etc. and actually find out what temeperature the first div down is. 5 degrees, 10 degrees .... below normal.

 

[Doofer]

I keep on meaning to do some runs with MultiECUScan connected to see a graph etc. and actually find out what temeperature the first div down is. 5 degrees, 10 degrees .... below normal.

I wouldn't bother - just replace it. Mine's been boringly well-controlled ever since I changed mine about 2 years ago. It takes a few minutes to get to vertical, then it stays there - regardless of how I drive, what the temperature is etc.

If it's moving then it's knackered. I don't remember it being that traumatic a job - probably a quarter of an alternator change-worth of stress, from memory. The drain down and refill takes as long as changing it.

 

[Roberto Blanco]

I agree with Doofer, I've also changed it a year ago and no problems since, the needle don't move a millimeter since the replacement even at -20 degrees. It is obvious that yours is about to "die".

 

[BrianMcL]

It's definitely working much better this morning with the gauge going up to the centre after a few minutes and staying there.

Previously it wouldn't move much from cold unless it spent a long time idling on a hot day, and as soon as I moved off it would quickly cool down again.

Big problem in the winter obviously as the flip side is that the heater just never warmed up much, no matter how long it was left idling.

Looking forward to seeing how much of a difference it makes.

 

[Roberto Blanco]

Big problem in the winter obviously as the flip side is that the heater just never warmed up much, no matter how long it was left idling.

The diesel engine will not warm up at idle like the gasoline engine, unless you have the additional and of course optional heater (webasto type). Trying to warm up the diesel engine at idle it's a waste of diesel, etc. To warm up after a cold start "Drive off slowly, letting the engine turn at medium revs. Do not accelerate abruptly".

 

[s130]

Yes I'm aware my thermostat is probably on the way out. I'm expecting it to play even more silly *buggers. Usually I'm the first to jump in and fix stuff. Just wish it was doing what it has started to do when I replaced the cam belt, belt running gear and water pump. Waste of good and expensive antifreeze and deionised water.

 

[Roberto Blanco]

Waste of good and expensive antifreeze and deionised water.

I recovered mine in a clean big bowl (10 liters, one used for washing clothes manually). Cleaned the spoiler inside where the antifreeze will drop from radiator with a clean and wet cloth prior to release and all was perfect. I'm thinking to an alternate method also, were you can use a plastic cone with hose under the radiator draining hole to recover the antifreeze.

 

[cjlar]

Well done Brian. I remember those rear bolts now. Amnesia must be a defence mechanism!

 

[BrianMcL]

Can't take the credit cjlar - it was my neighbour that found them. I held the mirror and light and he got stuck in with the sockets.

Mission accomplished though and that's the main thing

The car definitely runs much better and I'm not sure why but seems to be using less fuel around town at least anyway.

 

[s130]

Radiator draining etc. catchable and recoverable however I'm really struggling to remember if the Croma engine block has an engine block drain plug? Must be old age as I'm trying to remember back to when I did the water pump. Something tells me I drained the radiator via a lower drain tap but the block got drained when the water pump was detached.

Not to worry as I have full notes, eLearn etc and when I get my head back under the bonnet I'm sure I'll inspect, see and remember......hopefully.

My reluctance to dive in at this stage is because all I'm seeing/noteing is what I would call a lethargic thermostat to close down fully (safe mode of failure).

Also checked this afternoon and my local parts supplied has the thermostat housing in stock for a modest £29 retail inc. VAT (I get trade pricess anyway so will be less than this).

A firm failure will see me get the job done asap but at the moment I've so much other stuff on my plate it is more of niggling status query than a real concern or worry.

 

[Doofer]

A firm "don't know" from me I'm afraid, but I do remember that I didn't get much out from the radiator drain when I did mine. It emptied enough to change the thermostat without mess, but didn't need much refilling. So it was fine as far as changing the thermostat went, but I didn't count it as a coolant change.

 

[s130]

Thanks Doofer

Just looked on eLearn and they only talk about draining the rad. All coming back to me. Also looking at the pictures/diagrams it is a straight run down from the main thermostat vent directly to the bottom hose so the block should drain to stat level and then only dribble out.

Also they suggest removing the engine under tray and some pipework. I won't mess around when I do change the stat. Will be ramps out, nose up and undertray off. Least that way I'll get decent rear side visibility and access even if I don't need it.

 

[BrianMcL]

I lost 2 litres of fluid disconnecting and removing everything that I did so it's not the end of the world if there's not an easy way to save it for reuse. Mine needed changing anyway so I didn't even try but with a replacement cost of less than £3 I didn't think it was worth the effort.

 

[BrianMcL]

Welcome back to the broken thermostat thread!

I changed it for a new one a couple of months ago but a couple of days ago the needle rather than going up to the middle and staying there as it had been it is staying stuck at the left and not moving at all.

The heater's working OK and there doesn't seem to be anything else obviously wrong.

Has anyone got any ideas about what the problem might be this time?

 

[Roberto Blanco]

Hey Brian,

If the needle doesn't move at all, then is one of the plugs from the temp sensor on the thermostat. When you changed the thermostat, it possible that you didn't plug it correctly and now its off from the vibrations of the engine. Check the plugs from the both sensors. Good luck !

 

[BrianMcL]

Hi Roberto,
I checked the connection to the green plug on the thermostat was on tight but I didn't know there was another one.

I changed the nearside headlight at the weekend and did a fair bit of dismantling of the front of the car in the process. Is the other one anywhere near the front / nearside of the car?

 

[BrianMcL]

Well the new thermostat's definitely stopped working. Whether that's because it's turned colder all of a sudden or something else has gone wrong I'm not sure.

Other than the stat itself is there anything else that would stop the engine getting up to normal temperature?

 

[Roberto Blanco]

I am sorry for my late answer, been gone for few days, no internet. About the second plug thing, I was thinking at my old Fiat Tempra, which had two sensor in the thermostat casing, my bad sorry for misleading you. I have checked my photos taken when I changed the thermostat and yes, the Croma has only one temp sensor there. Did you solved the temp indicator gauge problem ?!
Now regarding the engine not heating up, check the radiator after you run the car for 5-10 min, if it is warm, you might had a bad luck and bought a faulty new Thermostat. It happened to me with an older Renault, so it is not out of the question, but the chances are very low. Check that radiator and if it gets warm or hot before the temp is hitting 90 degrees, then the thermostat is faulty and you should reclaim the warranty. Good luck !

 

[BrianMcL]

Thanks again for the advice Roberto.

Just checked the radiator after a 20 minute drive in town and the open road and both it and the bottom hose are both cold to the touch. The temperature gauge needle hasn't moved and the air that's coming out the heater vents is warmish but certainly not hot, even set to 32C.