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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - expansion tank woe (1500cc)

In working thru my cooling problems I have found that my header tank is poorly. The metal surround on the pressure cap aperture has corroded so badly that it has lifted and bent the neck. This was stopping the pressure cap making an effective seal. The pipe that goes down into the tank is also broken but does not leak, so far.

I removed the metal ring and cleaned the rust back to clean metal and managed to straighten the neck pretty much. So now my pressure cap fits and does not let water past the rubber seal on the pressure cap.

Is the metal insert on the neck required? It mates to the disk on the underside of the pressure cap but why? Can I just not fit it?

When I put the cap on (old 13lbs and new 15lbs) and blow in the inlet pipe I can hear air leaking from the cap. Its not from the seal between cap & tank (rubber to plastic) its from the little disk on the bottom of the pressure cap that does not seem to be sealing very well (brass to rubber). I know 15lbs is not much but i would have expected it to be sealed more than I can blow.

It also seems that new expansion tanks are no longer available, any one got good experiance of alternatives that fit in the same place?

Thanks in advance.

Richard
r parker

Seek second hand - and ask your friendly Rach if she's got one lying around :)
rachmacb

hello friendly Rach, I dont suppose you have one lying around do you?

I'm happy to exchange good hard beer tokens for it!

Perhaps we can come a mutually satisfying exchange :-)

email richard at e3design dot co dot uk

THANKS!!
r parker

Lol Richard - I'll drop you an email tomorrow morning and we can discuss it - pretty sure there's one on my spare!!!
rachmacb

Richard. I am not sure what you have. The original brass tank had no form of washer in the neck area. There was an aftermarket tank, made of plastic, which did have a stainless steel sealing washer and a carbon steel insert in the filler neck. Why the two different metals? Who knows. The filler neck insert rusted badly and the stainless washer held up fine over the years.

On the original brass tank, you could not straighten the filler neck, as you have mentioned doing, because the brass would break or the solder joint would be broken. The loose pipe you mention would be either broken, or the solder joint broken, if there is any movement at all. The brass, which formed the basis of the tank, tends to work harden and, after a number of expansion and relaxation cycles, develops any number of small cracks all over the body of the tank.

Any used expansion tank needs to be pressure checked before purchase/use. The best way to do this is to run a rubber hose from the water inlet from the radiator (small metal teat near the center of the expansion tank) to the tank over flow (small teat on the filler neck) to make a closed system. Then, attach a radiator pressure test gauge and pump to the filler neck, pump the tank pressure up to the rating of the pressure cap you are using, and see if the system will hold pressure. If not, the "new" expansion tank is of no use to you.

Within the last five years, new production expansion tanks, made of both brass and plastic, have been available through vendors in the UK. The plastic tank I obtained was a duplicate of the factory tank with two plastic "feet" or "legs" molded in to allow attachment of the unit to the inner fender. For MG use, the legs were removed and the original, factory, bracket was used.

Les
Les Bengtson

I have a spare too if Rach can't find her's

Steve
Steve H K-ser

Hi Les, thanks, I think your test idea confirms the caps are bad.

Its the plastic tank in 1500cc's over here (see pic). The pressure cap is hissing when I blow in it, the tank although a the inlet is a bit wobbly, holds pressure OK. If I understand your test it should hold to 15lbs and then 'blow' at at 15lbs and not just hiss. Is that right? I cant think I can blow anywhere near 15lbs!! But I think you are right and I should pressure test before refitting anything

Hey Steve, thanks for the offer!

Richard


r parker

£35 from Moss but if it means you can use the car and save the HG and possibly head then . .

http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=1332#60
N Atkins

My car's got an expansion tank from an MGB. The differences are very minor, and it seems to work okay. The siphon pipe on my old tank broke loose from the tank wall, hence the need to replace it.

-:G:-
Gryf Ketcherside

Hi N (Neil?),

I tried all the usual suspects for new parts, Moss are on backorder with no date for availability, ditto Rimmer, MGB Hive have no stock etc..I think I've found the one part you cant buy new for a midget! I love the look of the aluminium 'race' ones but not the price, hence the question if anyone has used anything else off a modern car. It looks
like our friendly neighbourhood Rach has one so I will take her up on the kind offer.

Richard
r parker

Hi Richard, sorry I keep forgetting it says N, the N is for Nigel

I saw rach offer I was just putting up an alternative if case that didn't work out for some reason

I know when I've been to a mate looking for a spare sometimes we can't find it but turn up other forgotten ones

more than once I've looked for something I know I have only to find it has already left home
N Atkins

LOL Nigel - it is still attached to my "spares" car - so, I'm confident that even I can find it ;)!

To keep all your fears at bay, I will check it fully before sending it to Richard, as I would hate for one to arrive faulty, so wouldn't like to do it to anyone else!!!!!!!

I did also offer him the option of the Bhive, but now read that he did try them, and they are unusually out of stock.

However, I have also blackmailed him with the fear that he will be leaving my poor horses with no grass if he doesn't donate to my "buying electric fence posts" fund ;)
rachmacb

LOL rach as you appear to have so many cars it might be you've already got rid of your "spares" car and forgot

it's great that you're helping Richard out
N Atkins

You could always look for a Mini Moke expansion tank. I have a feeling they are very similar to the Spridget one - even made of brass.

Wazza
w butler

Ya think Nigel ........!

Whilst not all of them are mine - there are some of mine not included!!!!! As everyone will see, Primerose isn't there :(


rachmacb

Yike, is that a dog or a small fluffy horse?

Just to let everyone here know that Rachel is, officially, a STAR!

She has agreed to sell me a spare expansion tank so I can get the x*x!x midget back on the road while we still have some sunshine.

Thanks Rachel, thanks BBS!
r parker

LOL Richard - that's just one of the doggies - the horses come a tad taller :P He also thinks he's very good at working on cars - but, then again, the hours he's spent around me and others working on them - he probably does know alot more than many!

Just hope that it passes ok now!!!!
rachmacb

Les I am curious now.

I have not seen one of the brass expansion tanks fail as yet and I have also noted that most traders have a good number of these brass tanks for sale at prices of around £10, that suggests they tend to out live their respective vehicles.

I bought one for my MGA a few years ago to capture any water loss due to expansion (the MGA design just allowed excess water to overflow to the road) and it has been brilliant.

Out of curiosity is it the brass expansion tanks that you have seen fracture and how many have you noted?
Bob Turbo Midget England

Wow Rach how many cars do you have! Is the blue midget metallic blue? I like the look of that.
C Carter

Lol - they aren't all mine!

The 1500 Midget? It's actually one of the two that are going to South Africa - I offered the use of my drive to the owner and Debs to do an engine change. It was chaurtreuse, but then had a respray to sort of bluey-grey. I did keep meaning to ask what colour it was meant to be - so if you want, I'll contact him before they go. (Of course, if you'd like to donate to their chosen charity .... :P!)

The other one is just boring old teal blue ;)
rachmacb

BTW Richard - your expansion tank is now in a bucket of nice soapy water being cleaned - and on a full inspection, it is totally fine :)
rachmacb

Many thanks Rachel.

I'm working towards ending this sorry saga of cooling, todays fun has been replacing every last rubber pipe is the system and sticking a hosepipe into every hole I could find! I found one hose completely full of crud despite earlier flushing. It looks to be the one that completes the circuit if the heater tap is closed, good job i've never closed that! I've also wired up a new digital temp gauge, pulled the heater box out to check the heater matrix, the flies & dead things in there were disgusting but the matrix looks OK.

So hopefully when the tank arrives I should be able to drop it in, fill it up and get back to driving!
r parker

Am looking for something to pack it in now and will get to the PO on Monday
rachmacb

"The siphon pipe on my old tank broke loose from the tank wall" Gryf, it's made out of brass...some lead/tin solder would fix that. BTDT
Alex G Matla

Richard,

for the heater matrix:

1) back flush,

2) half fill, shake, then empty

3) then foward flush,

4) half fill, shake, then empty

5) then flush until only clean water comes out

6) shake to make sure nothing loose is left inside

7) if it rattles repeat steps 5 & 6 as required

8) check or renew foam around matrix so that the incoming air has to go through the matrix and not any around the matrix

9) check or replace box base seal

10) check the fan is going inthe correct direction

refill system as previous instructions (in Handbook)

if you've put new rubber hoses check next year for surface cracks

if you ever have to change the coolant again on a car you dont know you could use Barrs Flush to clean out the crud

most tap water isn't the best water to use, I'd recommend distilled and premix the coolant so you know the exact ratio going in and have the correct premix for topping up

a video for you, he's obviously seen 'my usual advice' posts -
http://www.youtube.com/user/Universitymotorsltd#p/u/1/247RJqDnSGk

amd another you might find useful (not as useful as an owners Handbook) -
http://www.youtube.com/user/Universitymotorsltd#p/u/2/o3Bu6qkHRnM

N Atkins

Richard. Thank you for posting the photo of your Midget expansion tank. I have only one friend who owned a Midget and I seem to remember his having an MGB type of brass expansion tank. Mayhap, like Gryf, it has been replaced sometime in the past with an other than factory correct part.

But, it looks like your mates have you well covered. Good show. Makes life so much easier when you have good friends.

Robert (Bob). Sorry to take so long in responding. Wife had to have emergency gall bladder surgery and things have just begun to settle down again.

To answer your question, I have not kept track of the exact number of bad tanks I have tested over the last ten years. I have distinct memories of four bad tanks, one of which was due to how the system had been plumbed and three having either soldering problems or cracks due to work hardening of the brass the tank was made of.

The plumbing problem was when we purchased a 77 MGB for my daughter and found a Mark I radiator installed with the overflow on the radiator connected to the input/output nipple on the expansion tank (good so far) and the overflow nipple of the expansion tank connected to a nipple which had been brazed onto the header tank of the radiator, creating a closed pressure system. You can imagine how the expansion tank failed with major cracking along the seams. We purchased the car at quite a good price because it had been into "The MG Shoppe" in Tempe, Arizona four times for overheating problems and the owners were convinced that "Brit Cars are Junk" because the problem could not be corrected. Using retired zoo monkeys as MG mechanics had more to do with the problem than country of origin and the car served my daughter well for many years.

The other problems were, twice, solder which had quite holding the connection(s) tightly. Most commonly on the input line to the expansion tank that receives the coolant from the radiator. Easy to check because the tanks would not hold pressure when tested and, when submerged in a pail of water, bubbles came from around the hole. Resoldering corrected the problem.

One tank showed physical cracks across the long axis of the tank, immediately under the place where the cross strap goes--the one which fits around the tank and bolts to the inner fender. First noticed because of a small amount of coolant leaking in those areas, more of a weeping than a streaming problem. Pressure testing of the tank showed small cracks in the metal of the expansion tank. Cleaning the surrounding area, fluxing it, then applying soft solder to the area allowed the tank to be used long enough to source a good used tank.

Long way of saying that my experience is that some of the tanks are bad and any tank which is of the pressurized kind (rather than just a catchment basin) needs to be examined, preferably pressure tested, before purchase and use.

Les
Les Bengtson

Hi Nigel,

Thanks, good point about the fan motor direction as I did not note the wiring connection. I'll add it to the list of electrical things to check before startup as I removed a bunch of other unconnected cables that have been added over time while I was fitting the new temp gauge.

Les, your are so right about the help from the BBS. I hope your wife is making good progres, my girlfriend had that a few years back, its no fun at all.


r parker

Richard, as far as my memory goes the fan motor will wire either way and fan go in both wrong and correct direction - feel on input ashard to tell in cabin even when the fan is going in the correct direction
N Atkins

The new expansion tank has now arrived, many thanks Rachel! With the pressure cap attached there are now hissing noises when I blow into the pipe where the hose fits, unlike the old one. The tank is now fitted but I may now get chance to fiil the system and test until next week due to other commitments. So now I've got all new hoses, radiator, expansion tank and digital temp gauge perhaps I'll actually be able to go out & drive real soon.

Pics of new tank in place!


r parker

new hoses


r parker

new gauge, yes I still have to tidy the wires up around the back!


r parker

LOL no worries - it was a pleasure dealing with you.

Sorry it was such a big box, it was the only one that we could find that wasn't totally in pieces!!!

Glad I cleaned it now you're showing photos of it ;) If you need anything else drop me an e-mail, still got a few bits and pieces left on "Bitsa" and now she's not going to waste time going to the Concours competition, then I'll get on stripping her as I want the engine out!
rachmacb

Latest update:

IT WORKS!

With everything reconnected and filled up I have had the engine started. First quick test sat in garage shows no leaks from any hoses, all good!


Second, longer test, last night was to leave the car running to get up to temperature. After about 30mins the temp gauge was steady at 66°C (about 150°F). I was hoping that it would get a bit hotter (after all this to get it cooler!!) to open the thermostat as I think I still may have some air in the system as I was only able to add 3.8 litres of coolant and the stated capacity is 5.4L. I guess there must still be some of the flushing water left in there?

Next test, if the rain holds off, will be a few miles on the road to get fully up to temperature and engine load.

Anyone have any idea what the normal running temp should be and clever trick to be certain there's no air left in there?

Richard
r parker

Squeeze the larger rad hoses a few times to displace air bubbles. If there is still air in the system release the top hose to the heater and make sure that there isn't air trapped in there - wait until water flows out or top up if necessary and then refit.

Running temp should be around 87 C
Guy

Richard,

>>I was only able to add 3.8 litres of coolant and the stated capacity is 5.4L>>

that would be a big air lock at 1.6l, there’s always some water, and oil, left in after drain downs but possibly you didn’t drain or fully drain the heater and/or engine block

on refill did you have the heater valve open?

if you think you have 3.8l of coolant and 1.6l of plain flush water then the coolant/antifreeze mixture will be more diluted

Sorry I thought I put drain and refill notes on here but it was on another thread not this, following the drain and refill instructions in the owners Handbook I've never had problems

owners Handbook (Ref: 0058) - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

let us know if you still think you have air in the system after following Guy’s advice

if you’ve done a good job of cleaning then the cooling will be better, remember to allow for gauge discrepancy

ETA: best to use rain or distilled water in coolant mixture (for future top ups now)
N Atkins

Thanks Nigel, Guy,

Have spent today hunting air and found none so I guess there was water left after flushing. Luckily I added the antifreeze neat and followed it with water so I've got 2L in there so thats just under a 50% mix. That will be Ok for a car that lives in the garage.

After the checks I fianlly got to give it a road test. All seems Ok. It was in the low 20's today, general driving saw the temp raising to 71°C. Standing still saw it rise to 86°C. Most importantly this dropped quickly back as soon as we were moving again. Even a high speed blast on a dual carriage way seems Ok.

I think I'm going to get a bleed for the upper heater hose to ease future filling, but so far so good!

If the sun's out tomorrow I think I might have to do some more 'testing' rather than the gardening!

Thanks, everyone, for all the help.

Richard
r parker

Richard,
sun is out tomorrow so you must run your car to heat test it :)

if you need a note explaining this to excuse gardening I can do one for you :)

the water left in was perhaps you didn't empty heater matrix and/or engine, no matter if it was clean water but next time distilled or rain water is best (means you can't water the plants too!)

if you're happy all the air is out great

if later you have any concerns about possible hotspots or airlock then there is another simple method of checking

if you've not already done so £7 or £8 on an owners Handbook will be one of the best investments you can make with your car

owners Handbook (Ref: 0058) - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

ETA: just gently brushing out debris from the front of the radiator can make a difference to cooling as can a clear path for the air (i.e. nothing blocking like badges and lights)
N Atkins

Richard,
Sounds like you have all, or almost all of the air out. From that point on it will sort itself out. Go for your test drive, - just keep an eye on the temp gauge to see it doesn't start to overheat, although it should be OK.

As it heats up it will expand into the expansion tank (clue is in the name!) This will also dispel any remaining air from the system. When you get back let it cool and as it does so it will draw water back from the expansion tank to automatically top the main system - this time without air.

When it is fully cooled (i.e. the following day) check the expansion tank and if necessary refill (using correct antifreeeze strength mix) to the high mark (usually about 3/4 full) If you overfill it doesn't matter it will just pee a little on the floor as it heats up. A couple of cycles through this will have the system properly filled and with no air.
Guy

yeah sorry three ifs in a row looks like I was doubtful I wasn't just got stuck on the one word

I'd timed out by the time (word stick again) I saw the three ifs in a column

oil level in engine, g/box and r/axle and regular oil (and filter) changes of all three (as per (Hand)book, of course) also contribute a bit to engine cooling

and don't forget fan belt tightness (but not overtight to ruin your water pump)
N Atkins

This thread was discussed between 14/07/2011 and 30/07/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.