Air Bubbles in Fuel Filter

[RichardS]

2 minutes ago, Nigel Clark said:

Richard,

I'm glad to find you've retained your scientific curiosity and rigorous approach to research since we worked together more than four decades ago.

However, during those decades health and safety have assumed far greater priority. We should certainly not be inhaling petrol these days, it's far more harmful now than in the seventies when it contained lead!

Nigel

You're right about that Nigel. I still can't leave stuff along until I know exactly how it works. It drives my Wife mad as she thinks I should just accept that if stuff works, it works. 😊 However, I did use white spirit as that seems a bit less volatile than petrol but I did use a long pipe just to be on the safer side.

I'm still going to make that visit once I'm sure that she can make a longish journey without problems. The one problem I still have is during this hot weather I can see that the cooling system will not hold steady at 85 degrees as it does in cooler weather. She's not exactly overheating but , to my mind, the performance of the cooling system should not be so marginal that ambient temperature affects the cooling ability, although I might be on a losing battle with this.

Richard

 

 

[Nigel Clark]

Looking forward very much to meeting again soon, and comparing notes on our GT6s.

Sorry to say, the GT6 cooling system is marginal for hot weather. There are various threads on this forum with ideas and differing views on how to improve cooling capacity.

My research and experimentation on this subject suggest the with the cooling system in good condition, airflow through the core of the (marginally sized) radiator is the most critical factor.

Nigel

[Chris A]

GT6 cooling: Maybe Triumph thought buyers would just be posers and only drive to the local pub and park up so us poor Herald owners would feel like second class citizens so the cooling system didn't need to be that powerful.

Time to duck and hide 🙊

[Nigel Clark]

2 minutes ago, Chris A said:

GT6 cooling: Maybe Triumph thought buyers would just be posers and only drive to the local pub and park up so us poor Herald owners would feel like second class citizens so the cooling system didn't need to be that powerful.

Time to duck and hide 🙊

Yep, duck for cover!

A good GT6 is reliable, well at least as reliable as a Herald. And as classic cars both will allow you to arrive in style at your chosen destination.

But if your chosen destination is more than 10 miles away, there's only one choice!

It comes with a 2 litre engine, 6 cylinders and overdrive.

Time for my tin hat.

Nigel

[RichardS]

1 hour ago, Nigel Clark said:

Looking forward very much to meeting again soon, and comparing notes on our GT6s.

Sorry to say, the GT6 cooling system is marginal for hot weather. There are various threads on this forum with ideas and differing views on how to improve cooling capacity.

My research and experimentation on this subject suggest the with the cooling system in good condition, airflow through the core of the (marginally sized) radiator is the most critical factor.

Nigel

That's interesting. I'll have a look through the "cooling" threads.

I've cleared a huge amount of crud from the coolant pipes by back-flushing the entire system from the back of the block and rodded out some waterways which were completely blocked. At the moment the heating is such that it appears to hold steady during this hot spell if the heater valve is open so I feel it's not far away from being competent ..... but as soon as I shut the heater valve (which is essentially if one is to avoid heatstroke!) the temperature starts to creep up. Maybe that's just how it is.

Richard

[Peter Truman]

I get the impression that the GT6 Rad is the issue, the Stag has the Supergill rad option which supposedly significantly improves its performance and hot weather security, its been fitted to many Aus Stags to aid cooling. Now I don't know what the spec/design of the Supergill is, but could it (core) be adapted on the GT6 rad to improve cooling.

My Vitesse Mk2 which has a radiator of similar size/design, unfortunately had an accident when it first arrived in Aus in 74, woman backed into the wife in a shopping centre, the rad had to be rebuilt and they fitted a new and upgraded Aus designed rad core/matrix, and whilst the gauge goes from just under to 5/8ths of gauge travel on hot days it doesn't go near the top or into the red! 

Quite a few Stags and big saloons have been converted to Davies Craig electric water pumps incorporating PLC variable flows in place of the mech unit, which also helps cooling. I've thought about it for the Vitesse, I've worked out how to fit it but not bitten the bullet yet! I think I saw a pic of a very hot UK GT6 with the D/C pump fitted!

Whilst I've had the head off the Vitesse I've never removed the block so the block hasn't been mechanically cleaned, but I change the coolant rust inhibitor annually and have never found the engine block drain blocked/encrusted with rusty build up. I recently filled it with Nulon long life but will change every 2 years or there abouts!!

[johny]

As I understand it the Supergill is down to the design of the cooling fins which have more surface area and/or turbulent surface design allowing more efficient heat removal and this could be applied to any car radiator. Its probably more expensive to manufacture so would only be offered in cases where available cooling is at its limit and theres plenty of customers willing to pay the extra.....

On the other hand I dont think the original water pump is a problem on the GT6/Vitesse after all exactly the same unit is used on the TR6.

[dave.vitesse]

The OE Vitesse pump works fine, is reliable and easy to replace. I bought/drove Triumph's in the 1960's  and most people excepted that in very hot weather your car could overheat in those conditions. They were used as everyday cars and if you bought a Vitesse or GT6 meant you wanted more power. Also remember we had colder winters and not so hot summers, so overheating was less of a problem.

If you can find a radiator reconditioner who could provide an up-grade rad then that would be the way to go.

As for the Slant four and V8, this has an in block pump which takes a lot more time to replace, and some of the replacements pumps have been of doubtful quality which as caused coolant leakage and in worse cases a coolant dump in the sump. Plus nobody wants an overheated aluminium head!

Dave

[NonMember]

There's a lot of nonsense spouted about how Triumphs overheat and had inadequate cooling systems. Back in the 1990s, a colleague of mine ran his completely standard Stag through the then-current industry "towing" test - low speed, high load, high ambient temperatures - and it passed with flying colours. My Stag had a viscous fan failure and ran for a few weeks with no fan at all - otherwise all standard - only overheated if in stationary traffic. My GT6 is missing the cowl and has the heater valve jammed closed. It never overheats, although in traffic in the weather we had this week it does get hot. The cooling is perfectly adequate.

[Nick Jones]

I agree. For all it’s other mods my Vitesse has a standard cooling system and it just works. Yes, the temperature goes up a bit if flogging up an Alp behind a slow camper van on a hot day, or if holding 80+ on a hot day, but it doesn’t actually overheat. The high speed thing seems to be an airflow issue as if you run with the bonnet unlatched and “floating” (or more likely it unlatched itself) it cools to normal levels.

My GT6 has a Golf Mk2 rad all nicely shrouded in which works well, but was done because the rad it came with turned the rad shops test tank into a jacuzzi and £30 for a new golf rad seemed preferable to £300 for a record......

As regards the OPs “air” bubbles. Though these could indicate an suction-side air leak, it’s also possible that they are actually vapour from the more volatile fractions of the fuel drawn out by the combination of low pressure and turbulence in the pump valves.

Nick

[dougbgt6]

Well done Richard! You’ve solved a puzzle I’ve wondered about for years.

I’ve asked Pete, but he can’t get past bottoms!

Doug

[Unkel Kunkel]

On 13/08/2020 at 16:30, RichardS said:

Right .... in the interests of science I've conducted a few experiments with surprising results!

I took a new filter exactly the same as the ones I have fitted. There is no dip tube in these simple filters. The entry aperture is in the very bottom of the cylinder and the exit aperture is in the very top.

I attached a clear plastic tube to the exit spigot so I could suck, and, with the filter held vertically, dipped the bottom spigot into white spirit. I then began to suck gently and the liquid started to rise in the cylinder. However, the filter acts like a wick and you can see the liquid wicking up in the filter material ahead of the level of the liquid. By the time the level of liquid gets about half way up the filter, the wick level has reached the top of the filter and, as soon as that happens, liquid starts to rise up the exit spigot and into the clear tubing. It seems to defy logic but it is what it is. Inside the cone of filter material, it must be full of liquid even though the actual level of liquid outside the cone is only halfway up the container or lower.

It doesn't matter how hard I suck now. The level stays at about half way in the cylinder and liquid continues to exit from the top. A mouthful of the stuff now becomes a clear and present danger!

The really surprising thing is that if I stop sucking and just leave the end of the plastic tube in the air and leave the bottom end of the entry spigot in the liquid, the level stays the same in the filter i.e. the liquid does not run out even though the top end is at atmospheric pressure. What is more, if I lift the end of the entry spigot out above the liquid, nothing different happens. The filter just sits there half full of liquid. The filter material acts like a non-return valve which I never expected.

I can obviously blow the liquid out quite easily but, now that the filter is wet, when I start to suck again the liquid starts to come up the exit pipe almost as soon as the liquid touches the bottom of the filter material. It is now behaving exactly as in my photo above. I can tip the filter right over on its side or leave it vertical but it makes no difference .... as soon as the liquid reaches the filter material it starts to exit from the top.

However, this doesn't work the other way. If I reverse the filter the other way up and such through the bottom end, then the level rises right to the top of the housing before it starts to appear in the plastic tube. If I stop the suction, the liquid simply runs out of the filter as you would expect and it drains completely.

The filter material seems to behave differently in each direction. If you want the filter housing to be full, the only way to achieve it appears to be to mount the housing the wrong way round. 

In theory, I guess in would be possible to fill the housing inverted and then quickly connect it up the right way around whilst it's still full. However, those bubbles which seems to come into my filter from the bottom with the new fuel would presumably just re-establish the air gap again?

Anyway, where does that leave us? I suppose with the confirmation that having the petrol near the bottom of the filter housing is not an issue as the inside of the filter cone is full of fuel which is why the engine never seems to suck that air bubble through into the float chambers. I'm still non the wiser about where the bubbles in my incoming fuel are coming from. The research will continue! 😉

Richard

That’s very interesting.

Not bubbles, which I think indicate air being drawn in father than vapourisation  

but the “ partially filled fuel filter“ is something that I have noticed years ago  on two gravity fed petrol mowers as well as a pump fed  engine system where the filter is on the inlet side of the fuel pump

It makes no difference  if vertical or horizontal or  which way round the filter is used or if I prime it full first -it  soon results in same situation when engine starts.

Your thoughts on the filter “wicking” the fuel seem  very sound but the full explanation seems elusive.

It doesn’t have any effect on function at all (and of course the filter was not transparent we wouldn’t be aware of it!)

I have a vacuum pump ( with a spark-proof motor) - if I get a few moments this week I will  investigate further by drawing up petrol through a filter...