Automatic gearbox dipstick fluid level confusion

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mickthefitter
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Automatic gearbox dipstick fluid level confusion

Post by mickthefitter » Sat Sep 01, 2018 8:14 pm

I'm declaring my autobox gasket replacement a success, but have never been happy checking fluid levels on the dipstick with this hot/cold malarkey.

Here is the sequence of events, from two years ago to...this afternoon.

I bought the car two years ago with a leaky autobox. Checking the levels, hot, it looked way down, so I topped it up. Took about half a litre.
I've topped it up about twice since, 100ml each time. Always checked hot.

Fast forward to yesterday and the gasket change.
I emptied the ATF into a washing up bowl, and before refilling the autobox, used a Pyrex jug to measure what I'd took out by pouring it into another washing up bowl.

4150ml. 4 and a bit litres.

The book says, normal transmission drain, put back 3 litres.

So I put back 4 litres.

Dropping the car down off the ramps, starting it, running it for two minutes, and checking the dipstick on the COLD markings, it was too full. Bugger. The level was about halfway between the 'H' of COLD on the dipstick and 'L' of the HOT.

So, I drained out half a litre into that Pyrex jug. It now had 3.5 litres added to it, not 4.

Ran the engine for two minutes, checked the level again on the dipstick, on the COLD marks, now only just above 'L'. Not enough ATF. Bugger again.

Added back 250ml of fresh ATF. So now I'd added 3.75 litres of fresh ATF, not 3 as the book says.

Ran the engine for two minutes, checked the dipstick on the COLD marks (with the transmission now tepid, but not hot) and it was just below 'H', so I was satisfied.

Took the car for a half hourish drive to dispose of my old transmission fluid at the local refuse site, got back home, WITHOUT EVEN SWITCHING OFF THE ENGINE I left it to idle in PARK for two minutes, checked the dipstick expecting to see the level up to the 'H' on the HOT markings, and...

It doesn't even reach 'L'. It looks underfilled. And I went under the car and touched the transmission and it was very hot to the touch.

So I'm confused. It is very possible, having topped the transmission up hot when I got the car, I've been running it overfilled. Not that it seems to have had a detrimental effect. But this business of having two sets of dipstick markings for HOT and COLD, and knowing how COLD is a running engine and transmission and how HOT is one that's been driven is very baffling.

I used to think the COLD markings on the dipstick were not the preferred ones to use, but as things stand right now, I'm going to check the level after a cold start in the morning and if it looks right, I'm leaving it at that for the time being.

david painter
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Re: Automatic gearbox dipstick fluid level confusion

Post by david painter » Sat Sep 01, 2018 8:40 pm

Have you run it through all the gears park to 1 and back to park, two seconds in each gear this ensures all the oil galleries are full. Its the Hot level that is important as that's where the oil is running when up to temperature. Dextron oil expands a lot between Cold and Hot hence the two sets of marks on the dipstick.
Dave

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mickthefitter
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Re: Automatic gearbox dipstick fluid level confusion

Post by mickthefitter » Sat Sep 01, 2018 8:56 pm

It isn't Dextron in these is it Dave? It's older mineral type. Dextron buggers up the linings I think. I've done it both ways, hot and cold. It doesn't seem to make any difference. Always used to check the Merc hot after running it through all the positions. With this Marina 2, neither its own handbook, the later Haynes manual for 1.8s or the Autobooks manual that covers all models from '71 to '78 mentions putting it through all the positions before checking. Just letting it idle in Park for two minutes. Yet I'd swear blind my first automatic car, the MK1 Marina I owned in 1981, somewhere told me, either in the driver's handbook or the earlier Haynes manual I got for it, to put it through all the transmission positions to fill the galleries. Why that seems to have been deleted from later books I do not know

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mickthefitter
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Re: Automatic gearbox dipstick fluid level confusion

Post by mickthefitter » Sat Sep 01, 2018 10:06 pm

I had this page bookmarked http://www.p6club.com/content/borg-warn ... ic-gearbox and have just re-read it. Hot level checking it is then. THEY say you only need drive the car for 15 minutes to get it hot! The manual I was reading from says 30 minutes. And they say, run it through all the transmission positions and check it immediately.

As things stand I've still added more ATF than the manuals tell you to for a drain down and refill. If I need to add more when the transmission is hot, I'll be putting back the same amount as I drained off this morning, going by the COLD markings on the dip stick.

This article also tells you Dextron destroys the linings in these Borg Warner transmissions.


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mickthefitter
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Re: Automatic gearbox dipstick fluid level confusion

Post by mickthefitter » Sun Sep 02, 2018 1:24 pm

Oh my goodness. How hard can it be to measure the correct amount of oil in an automatic gearbox? It is another one of those simple jobs that seems to be driving me nuts because I can't tell what the hell is going on.

So this morning, I did cold start, once the car was stable on choke I left it for two minutes, as per all the guide notes, then put the 'box through all the gear positions for at least two seconds, as per Dave's advice and that on the Rover P6 forum web page on Borg Warner transmissions, and on the cold marks on the dipstick, it looked only half full. The level had apparently dropped since yesterday and my initial drive. I was then interrupted for half an hour by an interested neighbour who wanted to chat (and offer me some spanners he was clearing out) so I turned the car off. Once that was over, before my drive to get it hot, I added just 100ml of oil, guesstimating it would take the level nearer to 'H' on the cold level so as to not risk running it low when it got hot.

I did a 35 minute drive. I got my clean paper towel, put the shifter through all the positions, checked the HOT level, it was still below the 'L'.

I then proceeded for the next half an hour to keep adding 100ml, 50ml, 75ml, not wanting to risk overfilling the 'box, while it idled, waiting two minutes after each top up, then putting the shifter through all the positions, and checking the dipstick at least twice after each top up. Sometimes I couldn't even see a difference after I'd added some oil. Eventually I've left it about 3/4 full between the 'H' and 'L' marks on the hot section of the dipstick. I must have at least put back the half litre I drained out yesterday morning, when the cold levels on the dipstick were telling me I'd put too much oil in.

And what's this about all the technical books saying for a normal drain down, not including the torque converter, you put 3 litres of fresh ATF back? I'm around about back up to that near 4 1/4 litres I drained out! It is complete nonsense! And my car doesn't have an oil cooler. You cannot miss things like an oil cooler. I've had all the cooling system to pieces on this car, and put a re-cored radiator in.

So, with the transmission casing too hot to touch and keep my hand on (I checked) according to the dipstick I now have a 3/4 full auto transmission. If I checked it cold, it would be overfull. Go figure....

So I will monitor the situation. I'm nearly out of fresh ATF anyway having wasted half a litre by an unnecessary drain-off. I've only a couple of tablespoons left from a 5 litre container. There is a slight misting on the outside of the transmission after my drive this morning, coming from higher up. It looks like the gasket under the circular casting retained by four bolts on each side of the transmission, which I assume is where a gear shaft is bolted in. It looks minor and it might pay me to check the tightness of the bolts, but other than that, I'm not touching it. I certainly won't be changing gaskets on anything involving planetary gears in an automatic gearbox. So the job I did, sump gasket and new filter, looks fine. Judging where the oil level should be, having drained it down, bit of a nightmare.

david painter
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Re: Automatic gearbox dipstick fluid level confusion

Post by david painter » Sun Sep 02, 2018 2:30 pm

You will be ok 3/4 on the hot marks. Don't worry about the cold mark just a initial fill guide properly hot so you cant touch the casing its likely to be on the full mark. I checked the factory data for the correct oil this am it says BLMC type F Trade name Castrol TQF. I think the plate you are talking about are the clutch servos see exploded diagram of main case.
Dave
bw65 main case.jpg
bw65 main case key.jpg

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mickthefitter
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Re: Automatic gearbox dipstick fluid level confusion

Post by mickthefitter » Sun Sep 02, 2018 7:55 pm

david painter wrote:
Sun Sep 02, 2018 2:30 pm
You will be ok 3/4 on the hot marks. Don't worry about the cold mark just a initial fill guide properly hot so you cant touch the casing its likely to be on the full mark. I checked the factory data for the correct oil this am it says BLMC type F Trade name Castrol TQF. I think the plate you are talking about are the clutch servos see exploded diagram of main case.
Dave
Yes they are the parts where its got a slight misting from Dave. I am not unduly worried. The leak from the sump and the dipstick tube union were far worse and now appear cured. After the last top up I've driven the car, not that far but to my parent's house, about four miles each way, and it is fine. It is possible, or maybe my imagination, that when I drove the car for 35 minutes earlier today, with the 'HOT' level appearing low according to my post-drive checks, the transmission was a little clunky on down-shifts, and may have been smoother when going to my parents after that last half-litre was put back. Or like I said, it could just be my imagination.

The Comma AQF blurb on their website says the oil is for Borg Warner transmissions. The 5 litre can was obtained for me by my local motor factors last year. I cannot shop at Halfords for things like this. It is like the antifreeze. Halfords has a bewildering range, whereas at the local motor factor in town I can pick up Bluecol and know that is right. When I went into Halfords the other day, I noticed their own brand range of motor oils....5W 30 specific to Ford, 5W 30 specific to Vauxhall, 5W 30 specific to Citroen.... Jeez. At one time I bunged Castrol GTX 20W 50 in the old Mk1 Marina and was happy I'd done a good job.

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