Diesel Glow Plugs and Temp

[Rich]

Hi all,

my Diesel van has always started fine, but this recent colder weather has made her a pig to start some mornings, this morning took about 4 attempts and a huge cloud of smoke. I got through a special offer in my local parts centre a full set of new NGK Glow Plugs, after making the assumption that 1 or 2 of the originals must be duff.

I thought it would be a very tricky job to change them, but it wasn't to bad when I changed them this afternoon. I was however astounded to find NONE of them worked when connected to a test voltage. All the new ones glowed as they should. The old ones wouldn't even get warm. So I will find out tomorrow morning if she wants to be an early starter or not!

Does anyone know if the original glow plugs are/were Bosch ones? Thats the ones I took out, and I am suspecting as they were all dead that they are the original ones.

One other thing, which is possibly more me than anything else. Where does everyones temp gauge (diesel) normally sit at this time of year? The vans sits at about 1/4. If the heater is off it will go up a touch more, if the heaters on speed 1 it sits on 1/4 and speed 2, just under 1/4, speed 3 it goes down even more. If your stationary in the the traffic the temp gauge goes down then even more with the heater on.

I have never experienced this, in the 1.3 the gauge sat at just under 1/2 if the heater was on or not, and slowly went up if I was sat in traffic. I just can't understand why the gauge goes down when you stop? The heater does work, but its not as warm as the 1.3's.

One method I tried (and i'm not sure how sensible this is) was putting a load of tape over the back of the grille to stop so much air coming into the rad, but this had made diddly squat difference. I put a new 88 degree stat in about 8 months ago and can't see that its failed already, but if people on here get warmer readings than me, I will change it again.

Could the supply hose from the heater water pipe on the back of the engine to the matrix be at fault? Mine is a mix match of bits of pipe made to fit and does have 2 rather tight bends in it. Would this make a differnce if the flow was slightly reduced?

The water pump leaks, but its not major yet, could this be loosing pressure in the system stopping it getting warm properly?

I remember someone saying on here once before that the Diesels ran cooler, but not sure. Any help gratefully recieved, Rich

[weasel2400]

Hi

your tempratures sound about right, the diesel maestros/montegos will always run a lot cooler than petrols as they have a thicker heavier block, I suport your idea with the tape so long as you make sure it dosent get blown into the fan or rad, I have a freind that yousd to put a plastic bin liner over the front grill and fix it by slaming the bonet down on it, the reson he did this is the warmer you can get a diesel to run the more fuel eficent it will be and the lower the emisions, althogh you need to be able to remove it when going on long trips ie: motorway, I am not sure why the gadge is going down wile stoped though, seems odd that does.

hope i've helped claify things a bit.

[e692wtt]

Why the temp gauge goes down when you stop... whether you believe it or not is down to you! :laugh:

A diesel engine is more efficient than a petrol engine (it converts more of the 'heat' (thermal energy) of the combustion into kinetic energy), but as diesel fuel has a higher calorific value than petrol it therefore burns less fuel than a petrol engine anyway (this explains the lower fuel consumption of equivalently powered diesel engines). A diesel engine, to some extent, will therefore 'seem' to run at a lower temperature as more of the thermal energy is converted into power and less into wasted heat (ie eventually passing into the coolant [also into the oil and the surrounding air in the engine bay]) than in a petrol engine. So if the same heater is used in similarly powered petrol and diesel models, the heat output from the diesel model will always be less good than that in the petrol model.

When the air is cold, it can happen that, with the car's heater on, the cooling effect of the air passing over the heater matrix can be enough to reduce the coolant temperature to below the temperature that the thermostat is set to open at. And as you put the fan on a higher setting (and more air passes the heater matrix) the coolant temperature is dropped further (you notice that the gauge drops as the heater fan is run faster ;) ). I have noticed this happen on various (petrol) Montegos, but it has to be a few degrees below freezing for this to happen.

When the engine is idling, the engine is burning a minimal amount of diesel, certainly a fair bit less than when the car is cruising in gear and a lot less than when the car is under full power (but is still burning its fuel more efficiently than an equivalent petrol engine would). So, at idle, less heat is passed to the coolant than when the engine is at higher revs and the heater output diminishes. But as it seems the heater is cooling the engine (as opposed to the radiator doing so) in this case, the coolant temperature is reduced by the heater matrix but the heat isn't then replenished as the heat input into the coolant is minimised as the engine is idling. So the coolant is further cooled and the temp gauge drops. Once the car is underway again, and the engine is burning more fuel, the coolant is heated up again, the heater output improves and the temp gauge rises again...


I would recommend covering part of the radiator with foil or plastic, as opposed to covering the grille up, to be honest- and see how it goes. Just keep an eye on the temp gauge.

[Jack]

My diesel (N/A) runs with the needle just below half in summer and just above quarter in winter (now).

Cool running is a known problem in winter hence radiator muffs (covers for the grille, often made with leather and sometimes with flaps to vary the amount of cooling air allowed to pass through). Some classic car buffs have them as a period accessory.

[E_T_V]

I'd go along with that. Basically the diesel engine just doesn't put out a lot of heat. Mine sits halfway up in summer (without the heater on) and 1/4 the way up in winter with the heater on and 1/2 way up today when my heater got blocked up so there is no water flow through it.

[Rich]

A lot of usefull information there.

The cold starting is superb now, with working glow plugs. It starts on the button even on really cold mornings now.

I'm glad my temp gauge issues are "normal", just seemed grossly different from any of the 1.3's I have had before.

Once the cooling system is working properly in the new year, the waterpump is now shot, half an hour sat in Somerfields car park and the trail of antifreze running down the car park came from me! I am having to put litres of water in there to keep her topped up. Have a new water pump, just haven't got time to fit it just yet! Also a new heater pipe from the rail to the heater will help make things better I think, and another good flush and we will see what happens.

Thanks all for your replys (and very thourough too I may add e692 wtt)

Rich

[weasel2400]

sorry to hear about the pump :banghead: , hope all things get sorted :)