Cautionary tale: Oil Pressure

[Theodore]

So, hoping this will help and inform any newbie 75 owners of the dos and don't when using their car especially relating to engine oil.

Last year, I bought my second 75 V6 – glutton for punishment – after my first, was found to have rust all along the seals. This car was the 2,554th car off the assembly line back in May 1999.

We all know about the impossible to read dipstick, which I have always found to be troublesome and this proved to be the case yet again back in February, after we had the car for only six months or so. After 2.5 hours on the motorway the oil pressure light came on so we pulled off at the first junction to find a garage to buy some oil. It was dark, we were tired etc...I put 1.5 litres in and the light still remained on. Only this time, there was blue smoke coming from the exhaust. The RAC said it could be a number of factors: sensor, pump, motor etc, etc...

To cut a long story shortish, we got towed back to Surrey. And the car remained under wraps due to Covid – garages were all shut.

Thinking about it some, I did some research on the engine oil management. The V6 has a capacity of 5.2ltrs. It takes only 1ltr to go from MIN to MAX on the dipstick – if you can read it.

The mid way point is somewhere from 4.2-4.7 ltrs with the minimum level at 3.7– 4.2ltrs. The general consensus was that I had over-filled the car. But this week I syphoned 3ltrs which resolved the smoke and stopped the warning light and a trip to the garage confirmed all was good and it even passed the emissions test, result.

But the maths doesn't add up. I had assumed I had no oil and put in 1.5ltrs but as I took out more oil than I had added, I'm now concluding that the car was already at MAX and the 5.2 capacity means how much oil it should take and not how much it will actually take, which by the looks of it is anything up to and possibly beyond 6.5 litrs, all because of an impossible to read dipstick!

Not so good however, was a long list totalling 18 issues which must be addressed, including coolant in the V, suspension arm bushes split and jacking point rusty and needs welding (both MOT fails) begging the question, how did this car pass the last MOT considering the car has been sitting under wraps for 6 months and has done little over 1k since we bought it? My mechanic was less than impressed and spelled it out quite clearly what he thought. I'm just disappointed and now face a bill of around a grand to put right. Which of course I will pay out, 'cause the car is stunning and a joy to drive.

Just thought I would share and warn new owners of keeping an eye on their oil levels.

[BRG75]

I have read somewhere on here, that MGR actually recommended (officially or otherwise) that the KV6 was better filled with oil only up to about the 2/3rds or 3/4 mark.

Something to do with (I think) the VIS motors.

[Theodore]

I would be happy if I could see the oil level at all. Biggest gripe is the shape of the black plastic tip on the dipstick. It catches oil all along its length so you're never quite sure where the level is. If should have been flat like all my previous cars, easy to see the oil levels

[victorgte]

I’m puzzled why you put oil in the engine in the first place? Oil pressure light can come on even when the level is correct.
The light is not a sign of low oil. Personally I’ve always run the V6 cars with a level just a shade under full and only check it first thing in the morning when all oil has drained off the dip stick. Clear reading is obtained.

[Theodore]

Put oil in just out of instinct, thinking I must be low on oil. I am hoping that it was user error that I had overfilled the car initially, but wondering why it waited 2.5hrs before oil pressure light came on and if it was just a case of overfilling the car as well as having all the new additional work done.

[Arctic]

Hi Theo.
always wait until the engine oil as dropped to the sump, after a journey at least 20 minutes or more, remove dip stick wipe it, then re-insert count to 5 and remove you should get a good reading, click the link below.

https://www.the75andztclub.co.uk/for...0&postcount=30

[SD1too]

Hello Theo,

You're right about the black graticule on the KV6 dipstick (apparently it is green on later cars). I place mine against a sheet of kitchen towel in order to see the reading!

There was also an MG Rover technical bulletin confirming the procedure for the KV6. The engine should be at normal operating temperature before switching off and waiting for five minutes so that the oil in the upper regions of the engine has a chance to drain down into the sump. This was devised to prevent falsely low dipstick readings.

BRG75 is referring to information passed on to us by a member who used to work with the KV6 engine management. It was indeed suggested that the oil level is maintained between MIN and the point half way between MIN and MAX. This was an attempt to stop oil being drawn into the throttle body and over the VIS actuators and their valves. I've tried this and unfortunately it doesn't work. My own theory is that this problem is caused by the cam cover mesh oil filters being too hot effectively to condense the oil vapour. My SD1 had this system which did not suffer from oil transfer to the intake system. The difference was that the filter was about ten times the size of the KV6 part and was mounted externally to the rocker covers, not internally as is the case with the KV6.

Regarding the other maintenance you mention, the coolant in the 'V' is caused by flattened 'O' ring seals which are available separately. When renewed and reassembled, ensure that the plastic 'Herbie' clips on the straight pipe are pushed fully outwards to make the whole assembly rigid. I have not suffered an 'O' ring leak since I did this several years ago.

The jacking point corrosion is something from which we all suffer. To put into perspective, it's just about the only rust problem you will have with a 75/ZT. The front lower suspension arm bushes are also known to wear but when this occurs varies depending, I would imagine, upon the speed the car is driven over rough surfaces (and particularly speed tablets).

Finally, being laid-up and covering low mileage will do a car no favours. Once it returns to regular use you will benefit from better reliability I am sure.

Simon

[Theodore]

Thanks guys, who would have thought checking the car's oil would be such a faff!
The coolant issue is identical to the issues I had with the previous car, although I'm told it is holding pressure, which is good.
As for the rust, it bothers me that it passed its last MOT in this condition as my mechanic - who is a friend - said he could not pass it as is. You then wonder what else is lurking yet to be discovered. It's just disappointing to be let down in this way.

[mileshawk56]

Theo, Technical Help Forum. " KV6 oil level check" 19th July. This is my experience and it works. Hope this helps. Chris.S.

[Theodore]

Thanks Chris