gary11

hi just one for the techies please 1998 Boxter 2.5 with new engine (porsche) dealer fitted 30k ago we have a slight coolant loss and presure increase at idle but not all the time there is slight evidence of oil in coolant but not a lot,any thoughts would be appreciated thanks a lot
G

Macster

Any evidence of oil in the coolant is a lot. There is no acceptable amount.

Doesn't sound good. You sure no one could have added some oil by accident to the coolant? Well, it was worth a shot.

A '98? How many miles on the car? Reason I ask is while there are certainly enough possible internal engine troubles to account for the oil in the coolant, my thinking (hope) is the oil is getting there through a bad oil/water heat exchanger. This has developed a leak over time due to well age, corrosion, possibly helped along by infrequent (at best) or no coolant drains/refills over the years the car has been in service.

Have you checked the oil for presence of coolant? Drain the oil into a clean drain pan and let it sit a while. Pour off oil slowly and carefully and look for water/coolant droplets in the oil. They'll remain "under" the oil.

Then remove the oil filter housing and pour its contents into another clean drain pain. Check not only for signs of coolant in the oil but for scary metal debris. I don't expect any cause you're not reporting symptoms that lead one to expect any.

You can have the oil analyzed to see if analysis turns up any coolant chemicals in the oil. Under these circumstances I could see an oil analysis justified.

If no signs of coolant in the oil, then the oil/water heat exchanger would be suspect #1.

If there is some coolant in the oil... I think you're looking at a compression test and even a leak down test. What one is looking for, and hoping he doesn't find it, is a crack in the cylinder, a crack in the head, "porous" block.

Before you do a compression test though you can remove the plugs and check their condition. What you are looking for is one (or more) plugs that are cleaner than the others. The clean ones strongly suggest those cylinders are getting a dose of coolant from somewhere. The coolant flashes to steam and essentially steam cleans the plug tip, electrode and if you could see inside the piston crown and all combustion surfaces.

A compression test probably called for and if one or more cylinders read low, a leak down test. Now it could be the compression is low cause a valve is not seating properly, even though the engine only has 30K miles on it. Not likely a valve but possible.

What the compression test results are determines your next steps.

If compression low and a leak down test eliminates valves then engine removal and tear down almost certainly called for. If a head gasket is leaking, or even if the head has a crack in it, the gasket can be replaced as long as the gasket surfaces of the head and block deck are good and the block straight. The head gasket may have failed cause the block warped. Rare but not impossible.

Or the head can be possibly (possibly) welded/fixed or even replaced with a new head. Again though one has to be sure the block is straight.

If a compression test finds nothing scary, and there is no coolant in the oil, then you're back to the oil/water heat exchanger.

If the compresison test finds nothing scary but there is evidence of coolant in the oil then again the oil/water heat exchanger suspect. But also an internal engine "freeze" (or coolant) plug is suspect. These have been known to fail and allow wholesale intermixing of coolant and oil. Mostly coolant ends up in the oil though. If this caught in time the engine can be salvaged, repaired, but it takes a shop with good Porsche Boxster engine rebuild/repair skills and money on your part.

Oh, one thing to consider before you go any further at all, is to take the car back to the dealer. While the labor and parts warranty expired on miles and probably time too, the engine is not that far out of warranty on miles (24K) and you might receive some goodwill regarding an engine replacement, if it comes to this.

Added: Oh, I see you are in the UK. I don't know where you are but check with Hartech and AutoFarm. These two UK based Porsche speciality shops both know these engines well and could possibly advise you.

Sincerely,

Macster.

gary11

Thanks I am a dealer and have our own workshops I understand the diagnosis processes for a head gasket job,however it was Boxster only type components that I wanted info on such as the oil /water heat exchanger where is this situated please? and is it hard to test?,it is possible the new owner may have put some oil in the coolant tank by mistake I suppose,there is a small amount of oil around the tank cap and system pressuises lightly causing a small dribble of coolant from water overflow but does not overheat I was wondering about expansion tank split/faulty cap or suspect water pump I propose a chemical test of coolant plus if negative for hydrocarbons a flush of coolant and new expansion tank cap for starters any other pointers would be much appreciated the car has covered 117k but the engine is new supplied by Porsche 3yrs ago and has covered 30k ish hence my warrany question thank you very much for your reply
G

Macster

Oil/water heat exchanger located on top of engine. This ls located on left hand side -- driver's side of engine USA cars -- at the back (flywheel) end of the engine.

Kind of a long narrow tall box with what looks to be fins around it.

A pressure test of the cooling system should establish if oil/water heat exchanger has a leak (or if there's a leak anywhere in the cooling system).

Water pump can be bad though it is a rare one that fails at 30K.

I might point out this applies to the oil/water heat exchanger too. But there is always the possibility the heat exchanger defective. As with the water pump the heat exchanger is not immune from manufacturing defects.

Also, the heat exchanger has IIRC seals/o-rings where it connects to the coolant and oil passages. If anyone of these bad then the unit can allow oil into the coolant, or vice versa.

Anyhow, back to the water pump: AFAIK, there's no way a failing pump could account for any oil in the coolant. But eliminate the pump if you want: Check the serpentine belt for sharp edges. If you find a sharp edge odds are high some accessory drive questionable cause belt is not tracking right. The edges of the belt should *not* make contact with any of the accessory drive pulleys.

Also, generally if water pump going bad it exhibits signs of a coolant leak. This takes the form of a whitish deposit on the water pump aluminum, almost always under the water pump pulley shaft.

Some of the other things I covered are while not unique to the Boxster engine are known problems with some of them. Cracked block, porous block, cracked head, and internal coolant plugs. If the car has overheated any a head gasket leak is possible.

In the case of the block, a crack forms at the top of a cylinder wall and for a while this can let coolant into the engine. Oil in the coolant not that likely cause there's generally not that much if any oil up where the crack forms and no pressure to force any oil that could be there into the cooling system. [Added: Well, there is combustion pressure but still the top portion of the cylinder above where the rings travel does not get any oil.] Generally the coolant makes its way into the cylinder. As the engine is used, the crack worsens and can continue down and around and finally a D shaped peice of cylinder wall comes loose and falls into the cylinder with disasterous results.

A porous block usually involves a bad casting. The cylinders are made by placing special inserts into the block casting mold and then molten aluminum flows in the mold and around and even into the insert material. The idea is the molten alum. permates the insert to make a pressure tight casting. The insert is used to provide a very hard, very wear resistant surface for the rings/piston, after proper finishing of course. If this process doesn't work right porosity is the result.

For reasons known only to Porsche there are at least two "freeze" plugs that seal the head and its internal coolant passages from the engine's crankcase. Corrosion, defective plug, or severe overheating and the resulting overpressure can cause one of these plugs to fail which allows wholesale intermixing of coolant in the oil.

If no coolant in the oil then chances are this is not the cause of the oil in the coolant.

Thus if the oil is free of any coolant contamination and there is only oil in the coolant the oil/water heat exchanger is in my layman's opinion where I would look first.

I'd be a bit leery of assuming the coolant acquired its oil from someone adding oil to the coolant fill tube unless the oil in the coolant was new (dark oil is engine oil that got into the coolant from some internal leak) and doing a coolant flush and refill just to see of the oil reappeared.

In my opinion a good cooling system pressure test called for. Of if the shop capable of it, removing the oil/water heat exchanger and checking the seals/o-rings for obvious problems and possibly pressure testing just the oil/water heat exchanger.

Sincerely,

Macster.