Brass Screw Heads on Raw Water Pump

[Goldie]

Guidance sought please!

I’m trying to do my routine water pump impeller change and can’t remove 3 of the brass machine screws securing the faceplate to the pump body.

A few months ago, I asked a boatyard to remove and clean the heat exchanger as the engine was running slightly warmer than normal. They took it on themselves to check the impeller as well (understandable) but then tightened the faceplate screws excessively to the extent that the O ring is visible being squeezed out and they damaged most of the screw heads as well - not noticed until time for an impeller change! The boatyard is 1000nm from where the boat is now so no point in asking them to sort it out.

I have removed 3 of the screws, but the other 3 are resisting all attempts - mainly, I think, because of the damaged heads which prevent much torque and will inevitably become more damaged the more I try. I really don’t want to remove the pump if I can avoid it as access to the bolts securing it to the engine means the job is a complete PITA as it means an open ended spanner turning each bolt about 1/8 of a turn at a time on each of the 4 bolts and even with the pump off, I still have the issue of removing the faceplate screws. Access to the faceplate in situ is ok.

When the faceplate is finally removed, it will be replaced with a Speedseal faceplate transferred from a previous pump of the same model and fortunately, I have spare bearing discs and O rings. Also, the Speedseal is secured by knurled machine screws, 4 instead of the 6 brass screws. I claim no engineering expertise but a thought has crossed my mind…

If all else fails, to remove the recalcitrant screws I could cut the heads off using a Dremel and cutting disc and pull the plate off that way. The question is, am I likely to have enough ‘stub’ to grip to unscrew what’s left? If not, what next? Cut flush and attempt to drill and re-tap using the faceplate as a guide? Sadly, only 2 of the removable screws are suitably positioned for the Speedseal leaving me with 2 threads to recover.

Any suggestions would be greatly appreciated please. As I said, I claim no engineering expertise so please be gentle! Thank you in anticipation.

 

[NormanS]

A hammer is an amazingly versatile tool. You might try unscrewing with as big a screwdriver as possible, and at the same time hitting the head of the screwdriver with a hammer.
My pump faceplate is secured with four knurled screws, and it's very easy to remove.

 

[penberth3]

It might be too late, but things like that I always tighten slightly first to break the bond. Gentle tapping with a small hammer can also help.

Often you just have to 'bite the bullet', shear or cut the heads and then drill out, clean and re-tap if necessary.

 

[RogerJolly]

How thick is the faceplate (guess you'd have that much exposed screw to work with)? I'd try a few heat cycles, maybe spraying WD40 or dedicated freezer spray on the screws.

If gripping the thread doesn't work, maybe try those 'stud extractors'. Can be a nightmare if they snap (now a worse problem), but might work if careful.

 

[RogerJolly]

How thick is the faceplate (guess you'd have that much exposed screw to work with)? I'd try a few heat cycles, maybe spraying WD40 or dedicated freezer spray on the screws.

If gripping the thread doesn't work, maybe try those 'stud extractors'. Can be a nightmare if they snap (now a worse problem), but might work if careful.

....am assuming they're not countersunk screws.

 

[Rappey]

Thats the obvious question, are they countersunk or could you grip the edge of the screwheads

....am assuming they're not countersunk screws.

Thats the obvious question, are they countersunk or could you grip the edge of the screwheads with molegrips ?
A good quality/new screwdriver with nice sharp edges and the tap of a hammer could work.
Maybe a cutting disc in a dremmel and fix the screw slot ?

 

[rogerthebodger]

If you still have a round had on the pump screws, use a drill chuck to tighten onto the round head and try to undo the screws with a reverse drill at slow speed

If the screw breaks off, I would then drill and tap the remaining holes and fit studs into the holes and fit wing nuts to hold the speed seal on to the pump

 

[Daydream believer]

Normally they are dome head brass, So nothing will grip the head ,Once the slot in the head breaks they are gone. One may as well file the head off & remove the plate, Then grip the stub with some mole grips firmly in ONE GO & unscrew. If it shears off. file flush & drill with a 2mm drill bit a centrally as possible having first spotted the centre. Then drill 4 mm(4.2 tapping size , but this is an existing hole) & tap 5mm to clean the hole & remove the residue of the old bolt.
Use the original plate as a hole drilling guide if not good at drilling. Start off with a 5 mm drill bit to form a very shallow sinking. This is just to guide the next operation, That should help you find the centre of the hole for the 2 mm & 4 mm hole The old screw may break free, especially if the hole is not accurately drilled, so take care not to jam the screw in the hole.
If the original plate is to be re used use 5mm socket head ss screws. It is much easier to remove/replace in a seaway using a "T" shaped allen key than a screw driver. Obviously the speedseal cover with knurled thumb screws should be the best option -if it fits

 

[Tamar]

Can you put the removed ones back in and tighten them up tight to take the pressure off the stuck screws? Worth a try. I have removed the same water pump screws with small mole grips

 

[Poignard]

Assuming the screws have cheese-heads, I would use good quality* pipe pliers to grip the screwhead and turn them.

They will either shift the screw or break its head off.

* good quality pipe pliers will have hard, sharp teeth that will bite into the screwhead to grip it securely; unlike the rubbishy cheap ones generally available which have blunt teeth.

 

[James_Calvert]

IRWIN 1602L3 Visegrip Long Nose Plier 4in, Silver https://amzn.eu/d/hhUSVon

I have a pair of small molegrips like these. They would probably grab the head of the machine screw firmly enough. Then very easy to apply just the right amount of torque to undo the fastening without breaking it

 

[Goldie]

Thanks very much for the replies so far. To respond/update:

I’ve tried the hammer ‘trick’ but to no effect. Also, tried tightening slightly first but no joy - they must have been tightened by a bloke with the arms of a gorilla .

The screws aren’t countersunk, but there’s very little to grip, I’ve tried .

Faceplate is about 3mm thick (guesstimated, not measured) so that will be the amount of stud to try and grip if it comes to that.

I’ve tried to relieve the pressure by tightening the ‘good’ screws but no joy.

Dremel to re-cut the slot will be with me when I next visit, and so will my heat gun and long nosed grips. Not much thickness of head to grip though…

I think the threads are M4 - is a screw extractor viable that small? If so, I’ll try it on one of the screws in a hole that won’t be re-used.

The Speedseal should fit - it came off the same model of pump - and is my ideal scenario.

 

[SteveA]

These little brass screws are a pain but you might try an impact screwdriver to get them moving. I've never had much success with stud extractors and if they break are almost impossible to remove.

 

[deeb]

Cutting the heads off and using a screw extractor is the absolute - absolute - last resort. They're brass, hence very soft, you could try filing a small flat on opposing sides of each and get a spanner, mole wrench, adjustable (whatever has a good sharp edge on the the flats), They'll come undone, probably fairly easily. At best a screwdriver doesn't impart masses of torque. A soldering iron is a good source of localised heat, An impact driver is commonly recommended but you can easily shear the heads clean off and the next step is a screw extractor - put that step off to until all else has failed.

 

[penberth3]

These little brass screws are a pain but you might try an impact screwdriver to get them moving. I've never had much success with stud extractors and if they break are almost impossible to remove.

Agreed. Using a screw extractor on M4 you've got about 2mm diameter of hard brittle steel. I wouldn't even try. On the positive side brass is easy to drill.

 

[pete]

Is there room to cut the screw slots slightly deeper with a junior hacksaw? They shouldn't be too bad to get out if they were removed a few months ago.

 

[Goldie]

Is there room to cut the screw slots slightly deeper with a junior hacksaw? They shouldn't be too bad to get out if they were removed a few months ago.

Possibly on one of them, I’ll give it a go. Thanks.

 

[jdc]

Is it possible that the yard used loctite on the brass screws? To have used red loctite would have been absurd - it needs about 250°C to soften and is meant for things which never need to come apart - but they may well have used blue which only needs about 100°C to soften: pour boiling water from a kettle onto the assembly and see what happens (or a soldering iron as suggested already).

I'd be inclined to get the pump off the engine anyway, it's a dreadful palaver but you probably are destined to have to do it anyway. You will have to if using an extractor, and you sure will have to if really heating it as that'll ruin the shaft seals!

 

[PetiteFleur]

When removed, replace with ss thumb screws, from ebay, easily removed with fingers or pliers. Coat thread with grease or anti seize paste.

 

[Poignard]

Is it possible that the yard used loctite on the brass screws? (...)

You never know.

As boatyards are likely not to have used Loctite when they should, I suppose it's equally likely they would have used it when they shouldn't.