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6v_man_in_12v_world
6v_man_in_12v_world, Restoration Shop Owner
Category: Classic Car
Satisfied Customers: 208
Experience:  Full service restoration shop specializing in pre-war, brass era, and full classic, but also up to mid-'60s.
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Rolls Royce Twenty: I have a 1928 Rolls Royce 20 with an auto

Customer Question

I have a 1928 Rolls Royce 20 with an auto vac problem, the petrol keeps running back to the main tank. How can I fix it please? My engine also over heats, very quickly, even though the radiator has been flushed through.
I either need a mobile mechanic who knows something about vintage cars in Surrey, or tips please - I'm better in the kitchen, where I can't break my nails!
I need help fast,
Thanks,

Caroline
Submitted: 1 year ago.
Category: Classic Car
Expert:  6v_man_in_12v_world replied 1 year ago.

6v_man_in_12v_world :

Hi Caroline, my name is Walter.

6v_man_in_12v_world :

How do you know your Autovac is draining back to the main tank? That really shouldn't be possible.

Customer :

Because I filled it up yesterday with a petrol can and funnel, and today, it was empty!

6v_man_in_12v_world :

Really and truly, the only way out for your fuel in that situation is it is either leaking from the Autovac or from the carburetor by gravity. Do you have a shut-off valve on the bottom of your Autovac?

Customer :

goodness knows! I do know that occasionally when I have left it standing for a few months in the past, I've had to fill the tank again, but it has never emptied like this straight away.

6v_man_in_12v_world :

Was there a strong odor of petrol in your garage thereafter?

Customer :

If there is a shut off valve, it hasn't been touched

6v_man_in_12v_world :

I'm going to provide a link -- just a second:

6v_man_in_12v_world :

Autovac diagram

Customer :

no odour of petrol only massive amounts of choke, carbon, or whatever it is, after not driving it out for a while when I started it yesterday, with a good few back fires

6v_man_in_12v_world :

Take a look at that. See on the bottom of the can "carburetor connection"? That should be closed whenever you park the car for an extended period. In a perfect world, nothing would leak, but all it takes it a little bit of trash in the carb for it to ask the Autovac for more fuel and thereby drain the can.

6v_man_in_12v_world :

Yeah, that's because all of that raw fuel dumped in the engine. Your backfires were raw fuel exploding in the muffler.

Customer :

there is a little tap, that I lift and turn, on top of the autovac that I switch on and off each time I drive it

6v_man_in_12v_world :

That tap serves to admit fuel to the Autovac, but has no control over what is already in the can coming out the bottom.

Customer :

grrrr. so you think that there could be a load of gunk in the autovac?

6v_man_in_12v_world :

It's possible. What do you know of the cars history? A tiny bit of trash in the carb is not unusual. If you've had chronic problems, it might be time to clean the interior.

Customer :

I filled up the autovac completely, drove about 1 1/2 miles, max. and popped it back in the garage. 24 hours later, it was empty

6v_man_in_12v_world :

I mean your ownership history (sorry if you are typing -- the system here is a little screwy and sometimes when it says the customer is typing, they are not).

Customer :

I share the car with my ex. we bought it about 5 years ago, and it had a new clutch and dynamo when we got it, and a massive service, at a cost of about $9,000 but other than that, not much has been done to it. Oil changes by a friend, but I am not in contact with my ex, who has the money and expertese in old vehicles, so I need to sort this out on my own. It was in a museum, I believe, for a long time, just prior to our purchase

6v_man_in_12v_world :

Ah -- long term sitting -- that's what I was looking for. Yes, it is possible trash has accumulated in the tank, but lets not worry too much about that at this point based on what you've told me. If you don't have that shut off valve at the bottom of the tank, see if you can have one installed. Shall we move onto the overheating problem?

Customer :

I've never used this e answer before = can I call you on the phone, or is that not the done thing?

6v_man_in_12v_world :

Unfortunately, they don't allow experts and customers to exchange personal information, so we're stuck typing -- but you're a great typer! Thanks for keeping up with the conversation!

Customer :

I would assume there is a shut off on the bottom, just not a mechanic! I drive, not tinker!

6v_man_in_12v_world :

It will be easy to find if it is present.

Customer :

It was sitting over winter, and I took it out last month for it's transport test, and it was fine, for 6 miles there and 6 back, and once again I filled the auto vac, but I expected that. I just thought that it should last more then 24 hours.

6v_man_in_12v_world :

It should, but even a very minor carb leak can drain the tank in that period of time. That's why the shutoff is there.

6v_man_in_12v_world :

On the front of your car are thermostatic shutters that should open as the car warms up. This allows air to flow across the radiator. Have you witnessed these opening?

Customer :

I keep the shutters open all the time

I assume you mean the ''grill''?

Customer :

nothing opens on it's own, as far as I'm aware???? I'm sorry, but you're talking to a real life dumb blonde here!

6v_man_in_12v_world :

Might be a bit of translation barrier, but if you have the ability to open them, that's what I'm taking about. So, next is the spark advance. Are you starting with it retarded and then advancing once running?

6v_man_in_12v_world :

That's o.k. -- so am I !

Customer :

yea, but you're a boffin! LOL

6v_man_in_12v_world :

You are probably correct, I think it was right around this time they went to automatic shutters, so you probably do have a manual control.

Customer :

Yes, I start it like that - I think!

6v_man_in_12v_world :

I'll admit, I had to look that up!

Customer :

where can I look up this sort of stuff? My ex won't even let me have the manual!!!

6v_man_in_12v_world :

The manual is about your only bet. I'm working from memory. You could buy your own copy. They are quite pricey.... but there again, nothing compared to the value of the car.

6v_man_in_12v_world :

As long as your shutters are open and the radiator flows well, there isn't much else to cause your overheating problem so long as the spark is advanced unless your water pump has failed.

Customer :

as I said, I only did a mile or so, and I could hardly open the bonnet to turn off the auto vac, it was so hot

6v_man_in_12v_world :

What did it do when it got hot -- boil over? Coolant spilling on the ground?

Customer :

It didn't boil over, but I wouldn't be surprised if it was close to it

6v_man_in_12v_world :

Do you have a temperature gauge on the dash, and if so, what did it say?

Customer :

I haven't has to fill the water for ages, last winter it had anti freeze put in

Customer :

it was at max

6v_man_in_12v_world :

Run it again and watch it. I know you said the radiator was flushed -- surely they flushed the engine, too. From that point I'd look at the water pump. Did you check the oil and was it cloudy?

Customer :

I must say that I was driving it with a lot of advance/retard, whichever way it is, as I wanted to just do a quick ''hard'' drive.

my friend flushed the radiator, only, I think....

Customer :

Oil is pretty clear

Customer :

although it hasn't had a change for maybe 4 years, but I've only done maybe 200 miles, if that.

6v_man_in_12v_world :

That's good. If the oil starts to get cloudy, that and the overheating could be indicative of a problem you don't want. We'll not bother discussing that. If you had the spark advanced (retard at start, advance once running) that's good. If you were trying to run it hard with it retarded, that could cause it to overheat quickly.

6v_man_in_12v_world :

Go ahead and change the oil anyway and once a year thereafter despite the short mileage. Moisture from the air will start to accumulate.

Customer :

that would have added to the problem, I'm sure....

But we've had over heating in the past.

Customer :

Ok, so oil change....

6v_man_in_12v_world :

Is there any consistency to the overheating?

Customer :

need the manual to find out what sort of oil!

it usually seems to overheat, but because I just do such short trips - cost of petrol here is extortionate, and Rosie guzzles it!

6v_man_in_12v_world :

Rosie is what we just named my new baby girl!

Customer :

AND I just take it out for the odd trip to the supermarket when it isn't raining!!!!

Customer :

AW! CONGRATULATIONS!!!!

6v_man_in_12v_world :

Thanks!

Customer :

well done!

Customer :

how old?

6v_man_in_12v_world :

If you're overheating consistently on short trips, you might ask your friend if he did a flow test whilst flushing it.

6v_man_in_12v_world :

Almost a whopping 5 days old now!

Customer :

oh WOW

So pleased for you

6v_man_in_12v_world :

Thank you.

Customer :

HAHAHA .... I can't ask the ''friend'' as he's got in excess of 123 vintage cars in all states, knows everything about them, but got obsessed with me, and dangerous..... even renting a garage opposite my house to ''spy'' on me.... I have had to cut all ties, sadly. - And that's not the ex!

6v_man_in_12v_world :

I would suggest having your radiator flushes done elsewhere!

Customer :

I do remember him putting a hose pipe in the top, and it was gushing out the bottom

Customer :

not sure what you mean by flow test though

Customer :

I was better off making tea!

6v_man_in_12v_world :

Gushing is good. The usual test is you cap the bottom with your hand, fill the top with a hose, and once full, remove your hand. The contents should dump completely in a few seconds. If it goes "glug glug glug", it's restricted and has poor flow.

Customer :

at some point in it's history, someone had fitted one of the pipes with a small meshed sort of cap, to collect any debris, and I noticed that it had collected some minute particles of something like rubber.... that was removed though.

Customer :

damn, I need a man!

6v_man_in_12v_world :

You need a man that knows how to work on your Rolls and that won't be easy to find!

Customer :

any man that can put his hand under the radiator would do for now!

6v_man_in_12v_world :

If I knew where to tell you to look for a mechanic in Surrey, I would, but I don't have any contacts there. Are you an RROC member?

Customer :

or even knows what a carborettor does, for that matter!

6v_man_in_12v_world :

Like I said -- good luck. You're more likely to find one that would rather be in the kitchen. So few people work on stuff anymore.

Customer :

it's RAC here, I think - you mean recovery???

Customer :

If so, I've been trying to join again for the last 3 days, but every time I think about it, it's out of hours

6v_man_in_12v_world :

Rolls Royce Owners Club It's international.

Customer :

Ah, I was with the RREC - enthusiasts, but didn't really make a point of doing things with them - most locally had mocern cars - ie 70's and 80's and were stuffy, and didn't really welcome a single lady to their world.

Customer :

spent , as I said, a fortune at the local RR garage, when we first got her, but even they had to call out the vintage guys, because they didn't know enough about pre war

6v_man_in_12v_world :

The RROC here has always been a pretty accepting bunch. Join, not so much for the social aspect, but to network, find help, get their classifieds, etc. Networking is king in the old car hobby.

6v_man_in_12v_world :

Let me do some checking. I might be able to find somebody for you. It will take me some time.

Customer :

is it costly to join, do you know?

6v_man_in_12v_world :

Just a moment, I'm checking

6v_man_in_12v_world :

Looks like they whack you with a $30 USD initiation fee and membership is $70. Not cheap, but not obscene, either. You'll get a nice magazine if nothing else!

Customer :

It's hard to find people willing to assist someone who is single.... and divvy, I really know so little about the mechanics of things. My ex and I did hill climbs and trialling all over UK in Austin 7's and Model A fords etc, but he was the one who could afford to do it. I'm as poor as a church mouse, and need to try and do this myself - can't afford $130+ 20% VAT at the local RR garage

Customer :

thanks for looking into that for me

6v_man_in_12v_world :

Though the club you might be able to find an individual who works from his home garage on the side. Guys like that tend to be more reasonable.

Customer :

I should try to go back to the RREC meetings again, - only went once, but right now, it's difficult to get involved in anything properly as I spend half my time in Cyprus, where I go to in 2 weeks, till Christmas, and obviously Rosie is not on my adjenda when I'm away

6v_man_in_12v_world :

There's bound to be someone out there who can help.

Customer :

however, I have a wedding booked for next Friday, and I HAVE to get her autovac problem sorted for that, or I'm dead meat

6v_man_in_12v_world :

Ah, that's the urgency! Well, take a look for that valve we talked about and practice running her over the next few days.

Customer :

if I find the valve, which I'm sure I will, what do I do about it?

6v_man_in_12v_world :

Turn it 90 degrees from where it is now.

Customer :

I'm frightened to fill it up again, and even take her round the block. As you know, we have tiny roads here, and if I break down, I'm stuffed!

6v_man_in_12v_world :

That's all part of the adventure!

6v_man_in_12v_world :

Just let it run at fast idle in your driveway. That will consume fuel, too, it will just take longer.

Customer :

not into adventures right now, just out of hospital after knee surgery - PAINFUL, and moving house in Cyprus 2 weeks tomorrow....

6v_man_in_12v_world :

Sounds like you've got your hands full.

Customer :

Ok, so I let it idle - that'll annoy the neighbours - all elderly! and shared private drive!

Customer :

that's only the half of it! LOL....

Customer :

Ok, so I let it run, or I take it for a little drive.....

6v_man_in_12v_world :

That's ok. Just remind them your car is elderly too.

Customer :

good idea.

6v_man_in_12v_world :

Yep, start out working her in the drive. Maybe later go for a spin around the village. As your confidence grows, you'll be making trips to the grocery store in no time.

Customer :

so you think if I turn the tap 90% might help?

6v_man_in_12v_world :

The valve on the bottom of the tank -- yes. If it's styled like the one in that drawing, a 90 degree turn should stop the flow of fuel from the tank to the carb.... just remember to open it again before taking out the car!

Customer :

so I literally just close and open it?

6v_man_in_12v_world :

That's all there is to it.

Customer :

As I said, there's no petrol in the auto vac right now, so I'll have to fill it before even taking her out of the gaqrage.

Customer :

So do I do that before or after filling it? and how or rather why do you think that might solve the problem?

6v_man_in_12v_world :

You just shut if off anytime you're not running the car. It solves the problem because you have a leak downstream that's draining the Autovac and this stops the flow of fuel from the Autovac.

6v_man_in_12v_world :

That's why the valve is there.

Customer :

but if there's no fuel there in the first place???

6v_man_in_12v_world :

It would only be relevant once you refill the Autovac and start driving the car again.

6v_man_in_12v_world :

The Autovac replenishes itself while driving, so ideally there's always about a quart of fuel in it.

Customer :

OK, so tomorrow, I fill the auto vac, then turn the tap 90% and 90% back, and then let her run for a while, or take her round the block?

6v_man_in_12v_world :

Sure enough!

Customer :

it does not seem to be replenishing it's self..... hence why I have to take it to pieces to refill it

6v_man_in_12v_world :

If you can drive-and-drive and it keeps running, it is replenishing itself. If it only goes empty after sitting overnight, it is leaking somewhere.

Customer :

can't be leaking, as I only put a huge piece of cardboard under her a week ago, and the only soiling is a couple of oil drips.

6v_man_in_12v_world :

Does it ever die on the road and not restart without refilling the Autovac?

Customer :

I filled it with 3/4 of a normal size petrol can - I think that's about 1 1/2 gallons in total - and empty after 2 miles max

Customer :

thank God, it's never died on the road - only once a couple of years ago, when I forgot to fill it up in the first place!

Customer :

I have no idea if it was empty at the end of the drive yesterday, only noticed today when I was going to drive about 12 miles, but didn't have the time to unscrew all the little screws again.... and obviously scared that it WOULD die!

6v_man_in_12v_world :

Your short trips make it hard to diagnose. Earlier, what you said indicated it was flooded, and quite a bit can dump in the carb without spilling out. If you can go drive ten miles without it dying, it is replenishing itself. If you're driving a couple of miles and letting it sit, it is either draining overnight or you're bringing it back just on the verge of empty. Just let it idle in the drive like we said (make sure it doesn't overheat) and if it goes 30 minutes, it is likely replenishing itself.

6v_man_in_12v_world :

You can reference back to this chat tomorrow if you have something new to report.

Customer :

when I fill it, I always fill right to the top - is that correct?

6v_man_in_12v_world :

They shut off a little lower than that, but so long as you aren't dumping on the ground, you'll be fine.

Customer :

Ok, Waler, I'll try that, and hopefully your suggestion might help....

6v_man_in_12v_world :

Please keep me posted. Hopefully we can get you sorted out before the wedding.

6v_man_in_12v_world :

Go back and read that link about how the can works. It will aid in your understanding.

6v_man_in_12v_world :

They're pretty simple.

Customer :

thank you. Have to hit the sack now, 2 am, and eyes blurry..... all the best with your little one. So I can somehow get this page back tomorrow?

6v_man_in_12v_world :

Thanks! Yes, I don't quite know how it works on your end, but if you come back, you should be able to access your account and find the chat there.

6v_man_in_12v_world :

Just checking-in, Caroline. Do you have anything to report on your Rolls?

6v_man_in_12v_world :

Hi Caroline -- your wedding was this weekend, was it not? How did you make out?

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