Greetings everyone,
I have been a silent reader of this excellent forum for some time now, and have finally joined as a member.
I have a 1998 TDi300 EDC Disco which I use almost exclusively for off-road driving (ok, also for the roads that get you to the off-road sites). It has 312,000km on it, and I have had it for about 2 years/16,000km now. During this time I have had a fair bit of repairs done on it, the biggest one being the head gasket that had to be done twice (the 1st time it was probably not done right or the part was faulty).

I have a digital thermometer installed in the dash with the probe attached to the engine head (i.e. not measuring water temperature but rather the temperature of the metal). When I drive the car uphill (and only uphill) it starts to overheat. This is entirely based on the digital reading as the original temperature gage will always around the midline. But the digital reading will go up well above 100C on long climbs to the point that I really have to watch it. On the day the head gasket blew (and the the head cracked) I was climbing a steep and long uphill road with no safe place to stop. By the time I stopped the car the digital reading was above 120C (while the original gage was only at about 3/4, not even in the red zone). Since then I have been more careful, but still, if I don't watch it the digital temperature reading will steadily increase to the danger zone. As I said, this only happens when climbing at approx. 2500RPM or more. If I try to keep the RPM low (2000-2200; 50-60km/H) I can control this to a degree. Using the a/c on long uphill climbs is out of the question. On flat roads everything is fine, the digital temperature reading is usually 70-90C depending on how hot it is outside. It is practically impossible to get it to overheat on flat roads, tracks etc, this even with a/c on.
Things that I have done so far:
1) Replace the radiator
2) Replaced the main fan
3) Replaced the A/C fans
4) Have had the timing set correctly
5) Replaced the turbo and intercooler and their hoses (d/t other issues)

The head gasket is good now. There is no leak to the cooling system. I don't think there is an airlock either, as this would (I think) affect the engine on any road and even while on idle. The coolent level is very stable, and I rarely have add any. I also don't have anything blocking the airflow to the radiator.

So I am wondering what should be the next step? I really want to solve this problem rather than manage it by reducing the RPM. I have read quite a few threads on similar issues, but with no conclusive recommendation/ outcome. It seems that each case was different.

Any ideas/input would be greatly appreciated

Cheers

Ady

I'd look at the water pump, thermostat and associated pipework. Also the oil pump, the oil, being cooled by the rad, I assume needs a reasonable pressure to get it round.

Mind, I don't know how you'd test them, or what to look for, when mine overheated it was the radiator!

Thank you Paul. I forgot to mention that the thermostat was replaced. I did not replace the water pump as there was no indication that it was not functioning well (not sure how to check). I will look into these things, but I still feel that I am missing something.
Ady

Ady Gancz said:

Thank you Paul. I forgot to mention that the thermostat was replaced. I did not replace the water pump as there was no indication that it was not functioning well (not sure how to check). I will look into these things, but I still feel that I am missing something.
Ady

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Unfortunately these vehicles do not respond well to the higher ambient temperatures combined with long highway speed climbs.
Sounds as if you have covered everything to try and cure the overheat.
I have had my current 300Tdi, also a '98 for about 7 years now, I live in a tropical climate my Disco responds as you have described yours does, it will run happily all day at speeds less than 80-90kph, at about 85degC or less but if you attack a long hill on the highway at 110kph by the time you've reached the top my in the coolant direct reading capillary type gauge is pushing 116degC, the in dash gauge hasn't moved much above half way. The gauge the Disco's come with is "normalised", i.e. it is only a rough indication of the operating temp of the engine.
It will usually remain stable within normal operation range of the engine, when I got my first Disco a mate said, once that in dash gauge is on it's way off the mid position and on it's way to the red, it's already too late to save the head gasket.
You have already done a god thing by fitting a direct coupled digital gauge, now you need to fit what is called an "engine saver" it is a coolant level warning device that lets you know your coolant level is low, the 300tdi engines water pump is way up top and coolant will quickly stop circulating if the level drops even a little.
In my opinion the way forward for these Discos is to use waterless coolant, a friend of mine has done the conversion and it is amazing how well it performs, no more low temp boiling because this stuff has a boiling point of around 170-180degC, but it is expensive and you need to remove all the water from your system and dry it out thoroughly before putting the waterless in. This results in lifting the boil point to a place you could not achieve, absolutely no pressure in the cooling system, giving all hoses, seals etc in the system a much easier time.
This will be my next move to try and save a disaster with mine.

Gazbo said:

......
In my opinion the way forward for these Discos is to use waterless coolant, a friend of mine has done the conversion and it is amazing how well it performs, no more low temp boiling because this stuff has a boiling point of around 170-180degC, but it is expensive and you need to remove all the water from your system and dry it out thoroughly before putting the waterless in. This results in lifting the boil point to a place you could not achieve, absolutely no pressure in the cooling system, giving all hoses, seals etc in the system a much easier time.
This will be my next move to try and save a disaster with mine.

Click to expand...

Sounds good. Think I'll look into this ..

Thank you so much Gazbo for this info. I have had the Disco overheat even on winter nights, when it is quite cool outside. There is a specific road which I travel a lot, which involves a 1000m ascent that takes about 40min with few flat stretches along the way. This is where I usually get the problem, the 2 main factors being the slope and the RPM rather than the ambient temperature. The slope is too steep to drive more than 80-90km/h (at least with my disco) but I often have to go much slower to control the overheating. I find it hard to accept that this is normal for this vehicle (or any vehicle for that matter), but if I can't find the actual cause for it, I am also happy to solve it by upgrades/modifications to the cooling system. Do you think a waterless coolant would help keep the temperature down or just prevent the boiling and hose damage? Other options I have considered is adding either passive or active vents to help evacuate the hot air from under the hood. I think this would help a lot, but I only found it mentioned in one thread. Adding an engine oil radiator/cooler was also suggested to me, though the space under the hood, especially in the front part that gets the cool air seems to be limited.
P.S. Where is the "engine saver" mounted? There is a warning device in the expansion tank which works well.
Many thanks!

Ady

Looked a bit into waterless coolants. I don't think they help reduce the temperature (at least not by much). They do, however, prevent boiling (which should not happen at operating temperatures even with standard coolants) and reduce pressure and corrosion. On the other hand, they are expensive, and are not yet widely available, so what happens if you have a leak in some remote location? At these prices nobody is likely to be carrying spare gallons of this stuff.

Ady Gancz said:

Thank you so much Gazbo for this info. I have had the Disco overheat even on winter nights, when it is quite cool outside. There is a specific road which I travel a lot, which involves a 1000m ascent that takes about 40min with few flat stretches along the way. This is where I usually get the problem, the 2 main factors being the slope and the RPM rather than the ambient temperature. The slope is too steep to drive more than 80-90km/h (at least with my disco) but I often have to go much slower to control the overheating. I find it hard to accept that this is normal for this vehicle (or any vehicle for that matter), but if I can't find the actual cause for it, I am also happy to solve it by upgrades/modifications to the cooling system. Do you think a waterless coolant would help keep the temperature down or just prevent the boiling and hose damage? Other options I have considered is adding either passive or active vents to help evacuate the hot air from under the hood. I think this would help a lot, but I only found it mentioned in one thread. Adding an engine oil radiator/cooler was also suggested to me, though the space under the hood, especially in the front part that gets the cool air seems to be limited.
P.S. Where is the "engine saver" mounted? There is a warning device in the expansion tank which works well.
Many thanks!

Ady

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Seems you may have a real flow problem with your cooling system, like a restriction in the block or head, or pump not circulating the coolant because it seems strange that it's getting so much temp up even with the cooler atmospheric temp.
Suggest maybe to try a high volume flush into the bottom rad hose, you would need the thermostat out. See if there is any coolant flow restriction.
Engine saver is fitted into the top fill plug in the top of your radiator, but if you have a device in the header tank that is ok too, I have my home made level switch in the header tank and it will let me know if the coolant level falls.
You have not mentioned if you've checked the water pump, the pump impellor may be broken or loose, it's the only other thing I can think may give the symptoms your Disco is experiencing. Is the pump turning freely?

Ady Gancz said:

Looked a bit into waterless coolants. I don't think they help reduce the temperature (at least not by much). They do, however, prevent boiling (which should not happen at operating temperatures even with standard coolants) and reduce pressure and corrosion. On the other hand, they are expensive, and are not yet widely available, so what happens if you have a leak in some remote location? At these prices nobody is likely to be carrying spare gallons of this stuff.

Click to expand...

I see your point, but with the waterless coolant in you've much reduced your fundamentals for coolant loss anyway, so much less likely to blow a hose or pop the WP seal or pop a welch plug, more likely a slow coolant loss if any, engine saver/coolant level monitor will stop you losing the lot.
My mate caries 4 litres spare waterless coolant, but since he's had the stuff in that's about 2 years now he's had no issues/leaks and drives the Disco long distance each and every day, 4WD trips on weekends.

Add electric fans, when you notice the temp getting high flick it on.

Waterpump first. With what you describe I fully expect the impellor to be somewhat worn or more likely loose on the spindle - its a known problem on these cars. It sounds like you have a reduced coolant flow through the system. Since the radiator has been replaced there wont be a restriction in flow there and it's unlikely you will have a blockage in the water jackets.

Waterless coolant will only reduce the cooling capacity as they are not as efficient and they will raise the operating temperature. They are not a panacea at all - the only thing it does is resist boiling and if you get to that point you've warped the head already. The system was designed to use glycol/water and if you change that you are running the risk of a cracked head again. Once I fixed my clogged rad, mine would haul a full load up in the Alps in blazing hot summer heat and never worried about getting too warm.

I think first thing is to fit a proper capilary temperature gauge and see whats really going on INSIDE the engine and not the outside.

Got these on both my tdi, brilliant bits of kit, no electric needed so reads temp all the time, and for 30 quid could be the cheapest fix or diagnostic tool you have?


http://www.ebay.co.uk/itm/TIM-Mecha...542214?hash=item4623375f86:g:SNsAAOSwaNBUeapk

Ok, thank you so much for this input!
I think I will first use a hand-held IR thermometer to compare my digital reading and the original gauge reading to various areas of the engine. Will then decide if I need a 3rd gauge. I will also replace the water pump and see if that works. Will report the results.
Cheers
Ady

Ady Gancz said:

I think I will first use a hand-held IR thermometer to compare my digital reading

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One small word of warning about IR non contact thermometers,

Be aware that the emissivity of the material including cleanliness can make a huge difference to a reading, plus they have a cone of measurement against distance from the measured surface. I use one every now and then to get a reference measurement that can easily be double checked later on if needed, but I am careful to double check with a touch probe if a "real" reading is required.

Cheers

P.S. Should I get the original LR water pump (Probably costly) or a replacemet? I see various brands or no names on ebay ranging from 13-54 quid. Any specific brand to look for?

Ady Gancz said:

P.S. Should I get the original LR water pump (Probably costly) or a replacemet? I see various brands or no names on ebay ranging from 13-54 quid. Any specific brand to look for?

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I've never found much wrong with Airtex or QH

http://www.paddockspares.com/peb500090g-water-pump-and-gasket-oe-supplier-300tdi.html

thank you Chris,
So, on the short list I have QH that is about 70 quid shipped
Airtex for about 55 shipped
and Bearmach for about 46.
Does the price reflect their quality?
Should I also get a P gasket and bolts?
Cheers
Ady

I've bought more QH for my cars than other pumps and QH have never gone wrong yet. However my current 300tdi pump is an airtex and is also running fine.... so really Id pick the cheaper of those two. Bearmach - they seem also to be good quality but I couldnt say one way or the other...

I would certainly buy a bolt set because the long bolts are likley to be rusty and may be stuck. I'd also consider getting new bolts for the water pump pulley it's only going to be pennies more and it will save you problems if one rounds off or shears. When the long bolts go back liberal application of copperslip or similar.

P gasket - again dirt cheap I'd order a couple to be honest since it costs very little to add it to the order. If it's not leaking I would leave well alone though - dont swap it when you do the pump. If it does start to leak - well you have the new gasket to swap it. If there is a leak already, or if you have a lot of trouble getting the long bolts out so its very likley its been disturbed then I would swap it.

And if getting some bits is a problem again since it's cheap and it can piggyback on the order I'd get a spare drivebelt and thermostat. Yes I've probably just added £20 to the order wtih all that - but if you have to order a p-gasket and then pay eight times its price of something daft for delivery you can see why that £20 extra makes sense..

chris-the-gerbil said:

Waterpump first. With what you describe I fully expect the impellor to be somewhat worn or more likely loose on the spindle - its a known problem on these cars. It sounds like you have a reduced coolant flow through the system. Since the radiator has been replaced there wont be a restriction in flow there and it's unlikely you will have a blockage in the water jackets.

Waterless coolant will only reduce the cooling capacity as they are not as efficient and they will raise the operating temperature. They are not a panacea at all - the only thing it does is resist boiling and if you get to that point you've warped the head already. The system was designed to use glycol/water and if you change that you are running the risk of a cracked head again. Once I fixed my clogged rad, mine would haul a full load up in the Alps in blazing hot summer heat and never worried about getting too warm.

Click to expand...

Have you used waterless coolant, do you know anyone who is using it?
Asking this because my friend and his son, both using it in much modded 300Tdi's, drive them like they've stolen them, never a problem since putting the stuff in, they both swear by it for taking the pressure off and preserving bits.
I believe there is no comparison between running constantly at a higher operating temp, and head cracking happening with water based coolants, there are such things a ""microboils", once the water component turns to steam, it no longer cools at all. Use of it is not for everyone, but then again many said electronics and efi would bring nothing but grief when we ditched carbies, but here we are. And progress is progress, bitter sometimes, but still progress.
On the water jacket restriction, my first 300tdi had overheating problems because some brilliant mechanic had punched a couple of the exhaust side rusted welch plugs right into the cooling jacket, must have then just put two new plugs over the top, I fished them out whilst doing a p gasket and timing belt job, they were sitting atop each other around cyl3, cooling system problem fixed.