Helicoiling the water pump

aprotogerellis · Jan 28, 2008

Hi there,

Time has come to change the waterpump on my 944 turbo and even the thought of removing those bolts makes me shudder. From what I gather there is a huge chance of at least one of the bolts snapping, if not more.

In preparation for this I'm looking to get a helicoil kit... Never having used one before I've got a bunch of questions I'm hoping some kind soul can help with... specifically:

1) In order to helicoil the waterpump bolts, what size of helicoil kit do I need?
2) Any recomendations on where to get one?
3) If the bolts do snap, is it likely that I will have trouble accessing the holes and helicoiling?
4) How long does the process usually take (i.e. helicoiling one bolt)

Many thanks!
Alex

peanut · Jan 29, 2008

ORIGINAL: 924nutter

try disconnecting the cooling fan plugs and let the engine get up to about three quarters of the way accross the gauge before tuning it off and trying to just crack the hold of a few whille the block is at its hottest. .

jeesus this is very risky. For a start the temp guages are very inaccurate and secondly the engine increases in temperature long after switching the engine off because the pump is no longer working. At 3/4 temperature the temperature would rise way beyond max with no fans connected.

Why risk your cylinder head.? its very expensive to put right if it doesn't work.

There are loads of previous threads about replacing waterpumps and helicoils etc the OP needs to do a simple search on here and also look on Clarkes garage site etc .
I wrote some advice only a couple of weeks ago about this very subject.

aprotogerellis · Jan 29, 2008

Thanks a lot guys - and I will look at the previous threads (oops)

924nutter · Jan 29, 2008

I have deleted my previous post in the interests of not having anyone destroy their engine, due to their mismanagement of temperatures, but I pose this question. If we invert your logic and examine the overrun temp, what temperature would it reach, exactly, if one just happened to switch it off just before the fans cut in? Only the water in the radiator would be cooled, because as you say the pumps stop running, so would would the temperature in the block run up to just over max, based on your assumption that allowing the temperature to increase by about 5 deg would send it way beyond maximum?

sawood12 · Jan 29, 2008

Even though the water pump has stopped running wouldn't there still be some circulation, albeit much reduced, of the water in the cooling system due to convection i.e. cooled and more dense water in the rad falling to the bottom and drawing up warmer water into the rad? If not then what is the point in having the fans run on after the engine is turned off?

Anyway, Helicoils are simple to install. I've used them in other applications. You have to size the Helicoil correctly for your hole and bolt size - a chart should be readily available from the Helicoil supplier, and you'll need the insersion tool. Have'nt a clue where you'd buy them from though - as I used them as an apprentice.

924nutter · Jan 29, 2008

I would say you are correct, but how long do they run on for? Well until the water in the radiator reaches 90 which is the temperature stamped on the body of the switch For ideal "thermo-syphon" circulation a tall thin radiator is ideal. Anyway we are getting miles away from where we started. I do not panic if my temperature gauge reaches 3/4 and the suggestion, before I deleted it seemed perfectly reasonable, and in controlled cicumstances infinitely better than the gentleman who was on his way back from Sliverstone when he noticed that his gauge was in the red. How long was it in the red before he noticed? He didn't cook his engine, even then, so I maintian there is no reason to believe than going to just 3/4 presents any tangiable risk. Stuck in traffic in the summer sucking in second hand air from the car in front you would probably see 3/4. How many people saw 3/4 on their gauges on the queue into Ragley Hall? Do you see my point now? As has been said on this forum before, and I wish I could find the thread which gave the details of the actual temperatures indicated by the gauge, people tend to over react when their gauge goes a little bit over to the right hand side of the dial. If this was really detrimental to the engine, 944s would be popping off all over the place.

peanut · Jan 29, 2008

Alex one of the previous replies I made on this subject was actually to a previous post of yours lol
here it is in case you didn't see it.
I think if you are careful and slow with the bolts you should be ok removing them. They often shear on the plain shank part where the body of the bolt is unsupported so in worse case scenario you still get a second chance to turn the remaining stud out with some stilsons.
I think the next time I have to do my waterpump I may be tempted to use studs with nuts rather than bolts.

quote from previous thread:

yes is the answer , very regularly.
The garage broke 3/4 of mine on my 928 and they are no differant on the 44.

If I were you I would recommend doing the job yourself if you ar happy to drill, tap and insert helicoils otherwise leave it to the garage and they can have the aggro. Its not an easy job,
In removing the bolts you need to turn very slowly 1/4 turns at a time . Alternate each bolt as you go . If they squeak or squeal be especially careful and take it really slowly so the bolts don't get hot from the friction and shear off.

If bolts do shear off you usually only get one chance to turn the sheared bolt out before it gets too mangled and you have to drill it out.
I recommend you only use a 9" or max 12" Stilsons nothing else. A stilson grips tighter the harder you turn it .You don't need to grop or apply any force to keep the jaws closed.
The more force you apply the more stilons grip. Be careful it doesn't fly off obviously.
They can succesfully grip a stud half the width of their jaws if you are careful.
Don't reuse the bolts get new and personally I would recommend helicoiling all the threads regardless if you intend keeping the car so you have an easy job next time and nothing shears when you torque it all up.