Troubleshooting

With no service records, I needed to get a early look at the condition of the belts because as we all know, a broken belt means a lot of work and big $$$.  Personally, I think people are a little paranoid about timing belts but there's that old ounce-of-prevention wisdom stuff that I try to abide by.

 Changing the belts and rollers was on my list but I wanted to be sure the water pump was OK too.  It would be aggravating to swap out all the belts/rollers only to have to go back in again to do the water pump. So.... checking the water pump starts with checking the condition of the water pump pulley. Generally I look for evidence that the belt is slipping on the pulley surface.  This "evidence" is pretty unscientific and, in my case, inconclusive.  I could feel a little lateral play on the water pump pulley and that is usually a bad sign. I had also  heard a chirping sound with the engine running which I imagined might be a roller with a dry bearing. Other stuff included a hint of a water leak and the usual oil film over the lower part of the engine - maybe a little worse than usual.  

The previous owner told me too that he'd had some concern for the cooling system but hoped that it was only a defective expansion tank cap. On Porsches, cooling system problems almost always end up being related to the water pump. I'm still dreaming at this stage though, hoping maybe it is just some leaky hoses. 

To find a leak, its easiest to put pressure on the cooling system and look for the drips.  To do this I rented a tester and sure enough found a few leaks.    

The 4th leak is coming from the cooling fan switch - which cannot be accessed without removing the cooling fans; which cannot be accessed without removing the oil cooler, which cannot be accessed....... You can begin to see where this is going.

The 5th leak is the worst because I couldn't confirm where it was coming from. I drained the radiator, removed the belts, tensioner's & rear belt cover and then re-attached radiator hoses. I could then re-pressurize the cooling system and confirm that the last leak was from the the water pump. You can see too, that I have a few oil leak issues so I'm starting to see an all-out front reseal and water pump job in my future. And so it begins.

To get the water pump removed, we have to remove the rear belt cover, the balance shaft gears (aka cogs) as well as the gears on the crankshaft. All of those are easy except the crankshaft gear. It is held in place by a large bolt that is torqued to 160 in lbs. This too is pretty easy if you have the right tool. 

To loosen the crankshaft bolt means somehow preventing the crank from turning. You might reason that you could put the car in gear, set the parking brake to hold the engine. True enough, this can be done on some engines, but, unfortunately, Porsche is not one of them. The most common solution is to remove the starter and, in its place, insert a flywheel lock. If you're going to have only one specialty tool, then it probably should be a flywheel lock.

Before you remove the belts or install the lock, you might observe the relative position of the cam and balance gears.  If you're not familiar with the various timing marks then now is the time to get comfortable with them, so you will know how to get the engine back "in-time."  I like to have the crank locked at TDC. 

Here, you can see I'm using an old style" pin wrench to hold the gear.

With the belts & tensioner out of the way and the flywheel locked , I can move on to removing the crankshaft bolt. Some people try the chin-up method but I've never had luck with that approach; the size 10 shoe together with a 3 foot breaker bar works every time though.

The lower balance belt gear will probably be stuck and you may be tempted to pry it off with some sort of lever. This almost never works and you risk damage to the surrounding components. Here I'm using a typical gear puller and you can see that it just barely clears the radiator. 

With the crank gears out of the way, I can remove the rear belt cover and finally get a good look at the crusty old water pump.

One note concerning the water pump - one of the nightmares that can occur when changing a water  pump is breaking of one of the small mounting studs. These studs are often  weakened by corrosion, apply heat to soften the thread locker and remove them carefully. Replace them with only grade 8 (or better) cadmium or zinc coated studs. Many vendors (and hardware stores) sell metric studs, very few sell the correctly hardened and treated ones. I'm still trying to find a source for these.

This is the time when you need to decide if you're going to replace the engine seals. If you're interested in how to do that follow this link, else continue here to prepare the new pump and start re-assembly.

Preparing the New Pump

One of my leaks (number 3) was due to the small nylon fitting that houses the turbo-charger's thermostat (yes the turbo has it's own thermostat). The fitting can also serve as a block-off if you have a turbo prepared water pump and want to use it on a non-turbo car. To prepare the fitting for use in my 951, I had to start with drilling out the inner wall. 

You can see the general position of the two thermostats, I would have replaced both of them with new but somehow I got an 80 degree main thermostat and an 83 degree turbo thermostat. I'm thinking they ought to both be the same, so I'll use my original. By the way, my new pump is a rebuilt unit from Zim's and comes with a gasket and an inner thermostat seal. Note: all of the water pumps shown here are updated pumps, more info on updated water pumps.

Note: before installing a new thermostat, check the condition of the inner seal, see above.

Re-Installation

Some people use a gasket sealer, some don't. I tried it once with no sealant and promptly developed a small leak. Since then I've always used the sealant. The down side is that it is extra work to clean the old sealant from the front of the engine.  You may be tempted to dig out an old scraper but beware, this aluminum is soft and scars easily. Both mating surfaces get a light application of acetone to insure sealant bonding. 

All that is left  is to place the pump on the engine and carefully tighten up the fasteners - careful not to over-torque. 

Final note: when I got everything back in place and refilled the coolant, I went back to the pressure tester to make sure I had all of the leaks. Everything seemed fine, so I just left the pressure tester connected with pressure applied. About an hour later I noticed that I had yet another  leak that seemed to be coming from the area of the turbo charger. I thought sure I was going to have to pull the intake and isolate the leak but then heard a faint hissing, thankfully, it was just  the bleed screw that was leaking.