Couple of theories on the diesel cool running problem?

[rovertone]

Likewise my normal running is 10deg lower than it should be (79/80 +/- 5deg depending on being under load or coasting) I suspect stat opening early being the cause. Up to normal on gauge at 3 miles and heater acceptable.
I have done nothing to resolve this as yet as I have had a problem at the other end of the scale, serious overheating when towing up long climbs in Spain. I found that my fan 2nd speed was not being triggered by the sender which turns out to have been a faulty (or wrongly specced) fan control PCB.

The rad is new so to complete the set I await delivery of a new water pump and stat so I will have the main cooling components back to near original and will be interested to see what difference it makes. I do not have an inline stat, advised against it if towing.
I am wondering whether the stat, as well as opening early, is also not fully opening given how fast the temp rises when under heavy load.

An earlier post mentioned 'airflow', as part of my problem solving i had the car on a rolling road under load to push temp up to check fan, using a high velocity static fan to simulate fan 2nd speed the temp wouldn't hold down, then we closed the bonnet, the difference was significant instead of 110c & rising it dropped to c 106c and held. As well as effect on the rad focussed air around the engine block.

I'll post the outcome when job is done.

ps I recently did a round trip to Portugal solo car, no caravan, no 2nd speed fan and had no issues at all. On the long climb (5% 6.5km) where i overheated with caravan, temp peaked at 84C!

[clf]

As has been said previously by others, in, as in my case the temp is only reaching 75, (coincidence? Lol )the stat would open very little, if at all. what is he point in having a radiator, or one so large? I understand that it may have been a cost cutting exercise, (fitting a rad already on these shelves) but surely they would have had access to smaller rads?

[Jim Jamieson]

We ran a diesel from new 2002 until last year. For the last 6 years or so I fitted a tailor made blank behind the main grille and the lower grille.

It was made out of high density foam, blue in colour so it was quite visible.
Gaining the right temperature was never a problem.

I should say it was fitted in the colder months and removed each spring.

[rovertone]

Probably standardisation, easier to requisition supply to the production line(s) if there is only one rad.
I have also pondered on how much efficiency is lost with the condenser and intercooler sitting in front of the rad, it must slow down airflow and at times present warm air, maybe that has something to do with rad sizing. With my overheating issue I also discovered I had an aircon problem so was probably 'superheating' the air first!

Do BMW's using this engine have the same problem?

[andymc]

As it happens, I've just had a new inline thermostat fitted to one of my cars - until now, the temp gauge had never moved more than a couple of degrees above the quarter mark since I got it back in late August. I'll give you a rough guide of how mine goes, in case it's useful as a comparison. It's a 2001 CDT (to which Marinabrian gave the once-over before I brought it home ) and has a FBH.

Today was the first chance I had to look at the exact temperature figures, on a ten mile run to Ballycastle and then the return trip later. On the way out it started off at around 40 degrees, then over the course of about 4 or 5 miles it got up to above 80. The last couple of miles on the outward trip involved stop-start driving combined with bends etc, necessitating slower driving and so the temperature didn't rise above 83.

The trip home was an hour later, so with some residual heat in the engine it got up to above 80 degrees much more quickly, within maybe a couple of miles. The highest temperature displayed was when it flickered up to 87 degrees a couple of times, but generally it varied between 82 and 86. Interestingly, when I floored it on a couple of uphill stretches (to see whether that would make it rise to/above 90) it actually dropped fairly quickly from maybe 84/85 to 81. Dunno whether that was because of a sudden inrush of cold air maybe?

The ambient temperature was 7 degrees. I kept to anywhere between 15-30 mph in restricted areas and up to maybe 70mph when overtaking once. Most of the time the cabin temperature was sitting at 22 on the driver's side and 21 on the passenger side. The car has just had a full service including a full engine flush, oil change and new oil/air/fuel/PCV filters. The (non-bypassed) EGR valve & manifold have just been cleaned, but I haven't yet put in a dose of injector cleaner - the bottle is sitting in the car waiting till the next time I fill up.

Within a day or two I might be doing a slightly longer trip, so if that happens I'll let you know if I see anything different once I'm able to cruise at motorway speeds for a bit. Not expecting to do any trip over 20 miles each way till next week though. Let me know if there's anything to which you'd like me to pay particular attention.

[clf]

Finally, got the video uploaded.

WARNING it is 25 minutes long, extremely boring, but it is my full commute journey of 10 miles on my way home from work. Viewing only the rev counter and OBD, my phone lens isnt wide enough to display the speedo. I felt the rev counter would give more information than the speed anyway. But the fastest speed I reach was for perhaps 1 mile at 75 mph. The journey consists of 1/4 mile to motorway, 4 miles of motorway, and 6 miles of 30/40/50 mph roads in moving but heavy traffic. When the hand brake light comes on, it indicates when I was stopped at lights.

This is very indicative of any journey I make. Be it 10 miles, or 70 miles. I did do a 70 mile trip recently, but the temperature only rose above 75 degrees, when I accelerated up a hill. It dropped back to 75-76 when it levelled out again.

I have ordered a sensor from Mat tonight, although it may take a couple of months to get it fitted, it will be an interesting exercise.

A question, I think I will have to remove the inlet manifold, are the seals normally reusable if in good condition?

[clf]

Originally Posted by andymc

As it happens, I've just had a new inline thermostat fitted to one of my cars - until now, the temp gauge had never moved more than a couple of degrees above the quarter mark since I got it back in late August. I'll give you a rough guide of how mine goes, in case it's useful as a comparison. It's a 2001 CDT (to which Marinabrian gave the once-over before I brought it home ) and has a FBH.

Today was the first chance I had to look at the exact temperature figures, on a ten mile run to Ballycastle and then the return trip later. On the way out it started off at around 40 degrees, then over the course of about 4 or 5 miles it got up to above 80. The last couple of miles on the outward trip involved stop-start driving combined with bends etc, necessitating slower driving and so the temperature didn't rise above 83.

The trip home was an hour later, so with some residual heat in the engine it got up to above 80 degrees much more quickly, within maybe a couple of miles. The highest temperature displayed was when it flickered up to 87 degrees a couple of times, but generally it varied between 82 and 86. Interestingly, when I floored it on a couple of uphill stretches (to see whether that would make it rise to/above 90) it actually dropped fairly quickly from maybe 84/85 to 81. Dunno whether that was because of a sudden inrush of cold air maybe?

The ambient temperature was 7 degrees. I kept to anywhere between 15-30 mph in restricted areas and up to maybe 70mph when overtaking once. Most of the time the cabin temperature was sitting at 22 on the driver's side and 21 on the passenger side. The car has just had a full service including a full engine flush, oil change and new oil/air/fuel/PCV filters. The (non-bypassed) EGR valve & manifold have just been cleaned, but I haven't yet put in a dose of injector cleaner - the bottle is sitting in the car waiting till the next time I fill up.

Within a day or two I might be doing a slightly longer trip, so if that happens I'll let you know if I see anything different once I'm able to cruise at motorway speeds for a bit. Not expecting to do any trip over 20 miles each way till next week though. Let me know if there's anything to which you'd like me to pay particular attention.

Thanks Andy, I know roughly the roads you are talking about. They are similar to some I would use and have tested on in and around Larne/Carrick. I can tell you, with the heater off, (which I think if you switch yours off, it will rise further ) it still doesnt get above 75-80.

There would be nothing I can think of for you to pay attention to, but maybe for your own interest, you should try it without the heater.

[Roverandover]

I too have the same problem. My car gets to 76 degrees within 5 miles or so but has never gone any higher. When I put full demist on the gauge drops to quarter when the fan kicks in. I haven't checked OBD for temp with full demist on yet.

I have an egr bypass and in-line stat fitted.

Will be interesting to see the results of a sender change.

Might have to try the rad blocking technique.

[clf]

Originally Posted by SD1too

Alan,

Your variable running temperature related to road speed suggests that your cooling system isn't pressurising correctly. It's perhaps worth looking at the expansion tank cap first.

By the way, your account of the cooling system's operation is basically correct except that in the case of the 4 and 6 cylinder 75/ZT engines, the OEM themostat is located in the return from the radiator, not in the hot flow to it.

Simon

Hi Simon, your post was the only one I think I didnt address, my apologies. The cap is an interesting idea. I have just ordered one, and will give it a try. I have opened it recently and heard some hissing, so assumed there was pressure there. There is also no apparent loss of coolant either.

The hoses are all firm to squeeze, warm and hot to the touch, with the outlet from the radiator feeling much cooler than the top. From that I can only assume the top hose stat is opening to some degree at least.

Overall, I am not overly concerned at the end of the day, because the temperature is quite stable and predictable. It is frustrating me more than anything else, simply because I read others' posts that state quicker warm up temps than mine, and higher running temps. With my thinking, the top hose stat could well be operating correctly, but the temp sender is sending misleading signals to the ECU. This I believe would cause overfueling. Less mpg, less power, more wear and tear, and more smoke. All of which could be avoided for a £10 sensor.

I could be wrong, but at the end of the day it will be interesting to eliminate it. Besides I should really clean out the intake manifold, whilst it is off lol.

[DMGRS]

I think it's important to remember the difference between the engine being thermally efficient, and the cooling system being thermally efficient - the L Series used in the smaller cars is also a 2.0 diesel, returns slightly better MPG (but lighter cars, remember) - but crucially, never has any issues sitting in the high 80s or low 90s even when cruising.

I think the cooling system on our cars places a very large thermal demand on the engine, rather the engine just being a very frugal design.

No real point to the above - just thought it's worth bearing in mind.