8v Gti Engine oil temp/oil cooler.

[Edwh0re]

Over the past two long distance runs I have noticed that my engine oil reading on the MAF display has been slightly higher than usual.  I have been used to my car running at 102° on average but it has been running at 108° on average the last week at motorway speeds (constant 70mph).  During a "rigorous" drive it peaked at 114°. 

This has concerned me a tad.  I have found the fan wasn't cutting in so today replaced the fan switch and rectified this, coolant levels are fine, there is no water in the oil, the water stays at a constant 90°.  There is no noticeable loss of power (it has a slight miss occasionally on idle, which I attribute to being overdue a spark plug change/possibly a deteriorating coil), and the car did a 170 mile drive today with a fuel economy of 43mpg at a steady 70mph.  Someone has suggested that it is time to change the oil cooler plate, which has never been done as long as I have owned the car - does this ring true to anyone? Is there an interval at which this is advisable?  Any pitfalls or problems to be encountered changing it?

I havent taken it on a high speed run since the fan switch was changed, but on the way home in 40/50mph limits and uphill it sat at 102° peaking at 104° and dipped to 100° when stationary.

As you can probably tell, I am paranoid as hell about this.  The car is high miles (181k) and right now I cannot afford to replace it or the engine, but any information I have found on the internet about Mk3 Gti 8v running temperatures is largely contradictory.  (Example, I have read of people having their 8v's run at 94-98°, but have read of track day cars peaking at 114-116°).

Finally, I first noticed this after topping up the oil last week.  I use a 10w40 semi synthetic, I noticed that the oil was low so topped up, it only went up to halfway on the dipstick with what I had left from the last oil change, so I used a different (but still 10w40 semi synthetic) to bring it up to the maximum.

Sorry for the essay, just wanted to make sure I had divulged every detail!

Ed.

[tweed]

old blocked oil cooler and maybe the oil/coolant hose.

I would take these off and inspect them. Try cleaning or replace. Good change oil pressure will be low and I'll also check oil pick up in the sump.

my 8v gti sits at 88 on average. My vr6 is about 108 I  think. So temp is nothing to worry about but is over the average.

[Wayne]

I think your worrying about nothing, my 8v was always up over 90/95 and that had low miles

[Edwh0re]

Its just how its been rock solid on the oil temps for 3 years, ever since I changed the thermostat (when I first got the car that was stuck open, and on a run the oil temp would go down to 74 degrees and the water would sit on 70)....

For it suddenly to start behaving differently gives me the willies Wayne.

Thanks Tweedy, I am going to have the car up on the ramps the week after next for MOT prep, Ill do the cooler and check the sump pick up at the same time I reckon.

[twotwofour]

Mine runs around 88/92 with 88k on engine

[Wayne]

and on a run the oil temp would go down to 74 degrees and the water would sit on 70)....

That seems way to low tbh, oil temp should be around 85/90 at least.

[madmanmart]

My 8v peaked at 120 degree on track and that was sweet.

But check for any blockages and is the water pump all ok?

[Edwh0re]

I am going to check for blockages, its recently had an oil change and filter, and the water pump was done along with the cambelt and tensioner 10k ago Mart.

I have it booked in next week for the oil cooler to be changed (along with oil and filter obviously) when it has its MOT.  Probably will engine flush it through then.  Also going to change out those plugs, and if the MOT isn't too expensive I will swap out the coil as well.

[Edwh0re]

and on a run the oil temp would go down to 74 degrees and the water would sit on 70)....

That seems way to low tbh, oil temp should be around 85/90 at least.

That is what I thought, so there was no surprise when the thermostat was changed and found to be stuck fully open.

[Edwh0re]

After my drive from Stoke to Essex last night, I think external temperatures are also in play.  Decided to see what the car would do, so I did a steady 75/80 most of the way back, at 80 it originally sat at 110° as I left Stoke, and the outside temp was 14°, by the time I reached essex, outside temps had dropped to 5° and the cars oil was running at 104/106° at 80.  Through the average speed check on the A14, 70mph saw it bang on 102°.

So perhaps I am being overly paranoid, perhaps the fan switch change out has helped a bit.