Club 80-90 Forums

Sorry, another overheating issue - its a long story but trying to give all info possible.
1991 High-top 115k but only 20k on replacement engine professionally fitted in Germany. Using 98Ron.
Until recently ran very well, 26 mpg over 5000 miles, cruised 70-85 no probs. Coolant needle almost always below warning light (warning light did not and has still not ever come on) but could go just above with continuous hard/fast driving. Fitted with oil temp gauge and oil cooler is mounted in front of radiator. Gauge almost always around 190f but could get to 210f with continuous hard/fast driving (red zone on gauge is 210f to 250f).
Then a full garage service in May - they changed oil using Comma mineral 10/40 (they said that was what was in before) and said coolant was OK. (previous owner told me coolant was changed in 2005)
Not driven much since service but about a month ago accelerating up a slight incline, coolant needle rapidly went just above warning light (fan kicked in) and oil temp went to just over 210f. This not happened before so carefully drove few miles home - still hotter than usual. Found coolant was at minimum level so topped up to half way between min and max with water. Oil was only just above min on dipstick so added half a litre - now close to max mark (perhaps on oil change the garage didnt allow extra for the oil cooler?) Even afer that seemed to be running a bit hotter than before but not used much.
Yesterday (fairly warm day) did 200 miles and when on motorway coolant and oil became increasingly hot even with careful driving. Coolant needle reached level of warning light and oil hit 210f. So drove with heating on full blast in attempt to stop oil temp rising further. Ended up doing 50-55 mpg at 2100 revs with coolant needle just below level of warning light but with oil reaching 230f. Off motorway at 30-40 with revs below 2000 coolant temp reduced slightly and oil down to 200f. In traffic with stop/starts/crawling, oil reduced to 190f and coolant increased with fan kicking in now and then.

So I used to drive hard with no probs and now I cant do 60 on a motorway! Is the problem that there is more heat being generated or that the cooling is less efficient? It seems to me that the oil temp in particular is higher and more volatile than before. As far as I can see there was no change in coolant/oil levels after the 200 miles yesterday.

Any ideas please.
Brian

I have the radiator fan cutting in and out on my hightop behemoth in 1st and 2nd gears. I have never had it cut in whilst in third and fourth, due i suppose to the amount of air going through the radiator.

Oil temp is a different matter, I know that the oil gets very hot on these, but with no temp gauge on mine difficult to comment on yours.

I would start by double checking that your oil temp gauge is functioning correctly. Remove it, and dip it in boiling water, to check accuraccy.

With an extra oil cooler you should not have a problem, how is the oil pressure. If the pressure was reduced, flow would reduce, and temp would increase. I often consider fitting an oil cooler, but was concerned as to the length of pipe run up to the front, and how it would effect oil pressure.

These engines seem to prefer 20-50 oil.

Thanks for reply.
I think the oil temp gauge is OK - it is going up and down roughly in line with coolant temp and both the coolant and oil gauges are reading higher.
I dont know about the oil pressure - as far as I know its OK. If the pipe run to the front oil cooler leads to lower pressure and so lower flow, woudnt the extra oil capacity and the cooling effect of the pipes and cooler more than offset that? The front cooler does get hot. In any case the increase in coolant and oil temp is recent whereas the oil cooler has been on there for years.

Maybe its the coolant system being less efficient than it was for some reason and so allowing the oil temp to rise and get to 230f - but I dont know what a normal oil temp is - but 230f seems too high.

Is 20/50 oil normally used? - if so could a change from 20/50 to 10/40 make the difference in temp?

Another thought - I always use 98Ron fuel. If the garage didnt know this could they have reset something assuming I was using 95Ron? If so might that lead to higher temps?

Just guessing/looking for ideas at the moment!

Brian

vwsween wrote:Sorry, another overheating issue -

So I used to drive hard with no probs and now I cant do 60 on a motorway! Is the problem that there is more heat being generated or that the cooling is less efficient? It seems to me that the oil temp in particular is higher and more volatile than before. As far as I can see there was no change in coolant/oil levels after the 200 miles yesterday.

Any ideas please.
Brian

Have a look at quagmires problem which sounds a bit like yours but about three responses from the end he say he fixed it.
Post subject: help me please!!!am getting really fed up now!!!
Looks like he just had a stuborn Air lock!
Good luck
Ken

does sound like a coolant prob, rather than oil.......

if they didnt bleed the system properly, OR left the heater switched to HOT when they bled it, you could have an airlock, which would show on your knee with the heater on, the heater would go cooler as the gauge dropped back to normal (17L of coolant takes a while to move round....)

I often consider fitting an oil cooler, but was concerned as to the length of pipe run up to the front, and how it would effect oil pressure.

Not a problem, many diesel owners have coolers up front 14.5 ft up and 13.5' back whatever way... I went mad (I was told!) and used 3/4" bore hoses giving me a welcome 2.5 litres extra capacity including cooler. Seeing just over 4 bar max and 1 minimum (hot idling)

Most use 3/8" or 1/2" bore hoses, much larger than the block galleries I think..

Oil temps...
210F is NOT too hot when pushing it, as its just under 100C... 110C to 115 max with a modern synthetic oil no problem, even 120C occasionally but by then pressure will definitely be seen to be dropping... it has been HOT lately, how many rows on your oil cooler, is it full width (235mm). The diesels need 19 or even 25 row to stay below 100C

Suggest a 15W-40 semi-synthetic and don't worry till you see 250F+... I've seen over 300 on the diesels without oil coolers..

Think your wqter cooling system is your main priority... if there is something wrong or different then try to trace that first, won't be helping the oil temps.

Thanks for replies.
The garage say they didnt mess with cooling system as coolant was OK.
HarryMann - what you say about oil temps reassures me a bit - but I am doing all I can to keep it below 230f/110c - speed 50-55 and revs just above 2000 and the heater full blast! - its no fun at all!
Think I'll have to get another garage to go over the whole cooling system.
Had a JP stainless exhaust fitted yesterday - sounds quiet (too quiet even)but I havent been able to rev it yet!
Brian

used to be 90c on the MkI Scirocco

Ian.

used to be 90c on the MkI Scirocco

Big difference with an engine in the back the same size and pushing two tons along thats the shape of a brick and twice the frontal area though

Use 15w40 and peace will be resumed.
10w40 is a bit thin, use it in winter if you want to, not at this time of year.
When sorting out my oil cooler kits I spoke at length with the wholesaler about the dia of the cooler pipes.
There is about 9-10m of hose, we decided that 5/8's would be best as it would reduce pressure drop.
3/8's and 1/2" were deemed too small and could be problematic.

Simon,
I have read up a bit about oil now and clearly 15w40 semi-synthetic is the way to go. Even the handbook shows that 10w40 is not suitable for the UK summer. What annoys me is that (as a mechanical idiot) I pay good money to so called VW specialists to do all the routine work fo me. They must have known perfectly well that they could do much better than 10w40 mineral.
Thanks for your help.
Brian

Just to finish this story in case others have the same issues. Oil changed today. Admittedly its a cool day but try as I might I could not get the coolant temp needle to reach half way, nor could I get the oil temp over 95c.
Brian

Good news, so you changed to a 15/40 and it sorted it?

Is this the same story with the petrol water boxers?

Chris