still topping up coolant

queenmonkey · 28 Sep 2016

Hi guys some of you might recall that i'd previously posted that my recently acquired ('98) 996 had needed constantly topping up with coolant (about a litre a fortnight). The guy i'd brought it from said it'd had a new rad fitted in the last month and i need to keep an eye on it. Well i've brought a new OE cap for it (suggestion on the other thread), no signs of a leak and expansion tank is quite new. I continue to top up and usually more after a longer (10 mile) run. I only tend to use it for short (4 mile) journeys.

Well thought i'd take it to my local indie. He thought it might be the pump but on inspection said it appeared fine. He took it for a drive and was impressed with how it pulled. He couldn't find a leak although commented on a very slight misfire (on tick-over) on cylinder 1. I didn't take much notice of that because for an 18 year old car i wouldn't expect a perfect tickover. He's suggesting that as (my) worse case scenario it might be the start of a blowing head gasket? Suggestion is to keep on topping up and monitor the misfire to see if it gets worse? They checked the coil pack on no1 and say it was ok.

I'm feeling a bit bemused now thinking that they might have been able to diagnose it. Not sure where to go now other than to keep topping up!!

Andyvvc · 28 Sep 2016

I was losing a very slight amount of coolant on my car when I first bought it. Maybe a few hundred mil each week - barely perceptible.

OPC said that was normal and pressure tested the system - no leaks.

My Indy said it wasn't normal, didn't bother with a pressure test and just removed the front bumper....some ever so slight crusting of dried coolant around the bottom middle of the front rad. Time for a new radiator!

No issues since.

If no one has taken the front bumper off to check hoses and rads....that's the first thing to do :thumb:

Alex · 28 Sep 2016

queenmonkey said:
Hi guys some of you might recall that i'd previously posted that my recently acquired '98 996 had needed constantly topping up with coolant (about a litre a fortnight).

How many miles have you done since you bought it? If the system has not been bled properly when fitting the new rad, it can take a few journeys before everything is right. Is it a litre a fortnight or more like a litre in 2 occasions you've last done 4 miles?

There's also the possibility you have a leak (there's more than one radiator and about 40ft of pipe work). Leave the car running at home for about 20 minutes after you've been for a drive and warmed it up - see if it's peeing water out.

Listening to folks advice about throwing different parts at a fault without diagnosing the problem is as useful as doing the lottery (with the intention of winning the jackpot).

kas750 · 28 Sep 2016

Andyvvc said:
I was losing a very slight amount of coolant on my car when I first bought it. Maybe a few hundred mil each week - barely perceptible.

OPC said that was normal and pressure tested the system - no leaks.

My Indy said it wasn't normal, didn't bother with a pressure test and just removed the front bumper....some ever so slight crusting of dried coolant around the bottom middle of the front rad. Time for a new radiator!

No issues since.

If no one has taken the front bumper off to check hoses and rads....that's the first thing to do :thumb:

Good advice. :thumb:

Griffter · 29 Sep 2016

I'd have thought compression/leak down tests would have been sensible to confirm cylinder 1 doesn't have a head gasket problem.

Jam911 · 29 Sep 2016

Similar issues on my 997 only that I need to top up a bit more each time.

The problem is crusty leaking hose joints front and back.

Engine out to fix and very expensive.

I hope your leak is not as bad as mine

infrasilver · 29 Sep 2016

Jam911 said:
Similar issues on my 997 only that I need to top up a bit more each time.

The problem is crusty leaking hose joints front and back.

I've had a crusty hose or two weep in the past, there is usually a bit of corrosion between the aluminium pipes and the rubber hoses. This causes the hose to expand and leak a little and it only usually happens when the engine is warm, which fits in with your story about it only happening when it up to temp.

queenmonkey · 29 Sep 2016

Thanks guys - looks like i've a few things to check out before fearing the worst!

318touring · 29 Sep 2016

Have a garage or OPC do a compression check on the cooling system. You didn't mention whether your garage did this or they just did a visual inspection and a test drive.

Head gasket is (almost?) never a problem in M96 engines. Is your garage a Porsche specialist? If not, take it to someone who is (very ) familiar with the marque.

Your other radiator(s) might be leaking - you'll need to take the bumper off to verify, if you haven't done the compression test.

If you have to get work done in the cooling system, might as well change your water pump (if it's the original).

Good luck and report back when you have the time.

deMort · 29 Sep 2016

I remember your last post .. far too many miles by now to be an air lock .

Garage has looked at it so no obvious signs of a leak .. they would need to do a pressure check to be certain , not sure if that was done .

Slight mis on no.1 but coil pack ok .. thats not so good , changeing the plug would be usefull as a mis on a single cyl is .. coil / plug / injector or something on compression ( coolant would fall into this ).

I would take out the plugs on that bank and compaire , a coolant issue even a slow one will tend to show up on the plug colour for that cylinder .

This is worst way though but if you are topping it up every 10 miles then its a pretty bad leak which if it was external should be obvious .

Only place its not obvious is the heater matrix ( radiator inside the car ) see if you have a sweet smell comeing through your air vents ( antifreeze smells sweet ) or damp carpets to rule that out .

I would suggest at this point that you have the plugs removed and inspected .. also to have the car left over night with no plugs in it to see if coolant is present in the cylinder the following morning ( garage has to scope the cyl )

My concern at this point is D chunk .. atm it could be headgasket , if it hydraulics is pretty bad .

Ive seen an m96 this week with hydraulic lock and suspected D chunk , rare but it does happen im afraid .

Worst case i know but the best advise i can give you .

infrasilver · 29 Sep 2016

318touring said:
Head gasket is (almost?) never a problem in M96 engines. Is your garage a Porsche specialist? If not, take it to someone who is (very ) familiar with the marque.

Agreed, its more likely on a 3.4 to be a cracked head than a head gasket failure but you need to check the cheaper things first.

queenmonkey · 2 Oct 2016

Hi Demort, and thanks for your thoughts. I haven't used the heater as yet, since buying the car. I'll try it today. The garage were vague on matters but certainly hadn't done a pressure test.

I've probably done 50 miles over three separate trips this week now. The level in the expansion chamber has gone down (couple of inches below min) but when i unscrew the cap (to top up) it lets out pressure and returns to between min/max.

How long should the system remain pressurized?

Alex · 2 Oct 2016

Until it's stone cold. The pressure is only created by heat and then drops again when back to cold (several hours later). When you release the cap when it's hot, it isn't returning back to 'normal' and will shrink back to a lower level when cold. Only remove the cap and check the level on a stone cold system (same as tyre pressure on cars).

bakerboy4s · 2 Oct 2016

I had slight leak from coolant hose where it connects to rad. Only happened when hot due to expansion, replaced no further issues.
Loss was quite slow but obvs. was happening whole time when driving so overall loss was high.
As above remove front bumper check it out!

deMort · 2 Oct 2016

You have put approx 1 pint in to top it up in 50 miles ?

Thats not really a small leak , atm i think its needs to be pressure tested and left on a ramp over night.

My concern is the mention of a misfire .. hence i said pressure test with plug out so it can be checked in the morning just to rule that out .

A leak from the heater would leak into the car .. damp carpets , sweet smell etc so would not leave a trace when looking under the car for a leak .

still topping up coolant

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