Porsche Enthusiasts Club Forum
https://forums.tipec.net/

944S overheated, potential engine damage?
https://forums.tipec.net/viewtopic.php?f=25&t=23528		 Page 1 of 1
Author:  infrasilver [ Thu Aug 16, 2018 12:58 pm ]
Post subject:  944S overheated, potential engine damage?
My S has been running superbly over the last few months and it has managed a few track days but on Sunday I was driving along and when I stopped at a set of lights I noticed steam coming from the bonnet, I noticed the coolant temp light on and oil pressure very low due to the thin oil. I pulled into a retail park and popped the bonnet to find the expansion tank cap loose but not off, I've not topped the coolant up so was curious why this was loose, unless I had leaned on it? I bought some mineral water from said retail park and waited for it to cool down before topping up. It ran perfectly the rest of the day and the following day even sat in heavy traffic.

On Tuesday I was heading to Brands Hatch for the Porsche only track day (needless to say I didn't make it) but I only got 30 minutes into the motorway journey before the gauge started creeping up again, it was fine for 25 minutes but the last 5 minutes it shot up. Pulled over at the services and the cap was tight and no evidence of coolant leak. I let it cool as much as I could and topped up the coolant as it had dropped quite significantly.
I fired the engine up again and after a few minutes I got a blast of hot coolant out of the expansion tank cap, the pressure had built and the cap couldn't take the pressure. I watched it do this a couple of times before I shut it off again.

I have ordered a new cap but I am thinking the worst, did it cook the engine the first time it got hot on Sunday and pop the head gasket and now it is over pressuring the system or even crack the head, is this common, I haven't noticed any bubbles in the expansion tank and there is no white smoke/steam coming from the exhaust that I have noticed?

I'm going to top it up, bleed the system and run it up to temperature today as I haven't had time to look at it since it got recovered home.

Anyone had a similar problem and what was the outcome?
Author:  Matt749 [ Thu Aug 16, 2018 1:52 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Sorry to hear you've got problems with your new ride. I'd take the spark plugs out and see if they've been steam cleaned. It's a quick and easy way to check if the HG has failed.

Good luck with it.
Author:  tr7v8 [ Thu Aug 16, 2018 2:14 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Possible HGF but the cause could be knackered water pump, jammed thermostat or something else. Are the hoses hard, e.g. with pressure?

If the coolant gets very low they will air lock, even though the header tank is full.
Do not overheat it, you will kill it!
Author:  scam75 [ Thu Aug 16, 2018 2:28 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Probably not killed the engine but every chance it could be the HG. They should actually be done every 10 years or so and if there is no evidence of this it will most likely look like a cheese grater by now if its not failed completely. When mine finally gave up the HG was in very bad shape upon removal. If you know the HG has been changed recently then its a different ball game but some are still on their original HG which will almost certainly be decomposing to the point of failure by now.

Stuart
Author:  infrasilver [ Thu Aug 16, 2018 3:01 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Just topped up the coolant and bled the system. Ran it up to temp and the fans kick in correctly, not running hot on tick over and no bubbles coming from the header tank with the cap off, refitted the cap and all seemed fine still.

I squeezed the top hose and that does feel very hard and under pressure so I didn't take it for a run.

It had a full engine rebuild around 3000 miles ago and had a new head gasket then but all the basic tests do seem to point to the system getting pressurised by the cylinders. Still no steam from the exhaust so hopefully the cylinder pressure is higher than water pressure and no coolant is going into the cylinders. I'll compression and leak down test as I have the recent figures from when it was rebuilt and compare to what it is now, if nothing else but to find which part is bad.

Will order a new head gasket as I'm sure this is the problem, its hopefully just the gasket but I do have a spare S2 head if this is compatible and there are issues with the current one.

Is the S2 head a good option or a repair to the S head better?
Author:  Rhett [ Thu Aug 16, 2018 3:17 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
The S2 head is not truly compatible with the S head, They are physically different as one is for a 2.5L engine, the other a 3.0L, and I believe there is a slight design change to the cooling galleries too...I had looked into doing this at some point too and was advised by the Pelican forum members that it wouldn't work... :( . However, if someone has done it, perhaps they can advise?
Author:  infrasilver [ Thu Aug 16, 2018 4:48 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Rhett wrote:
The S2 head is not truly compatible with the S head, They are physically different as one is for a 2.5L engine, the other a 3.0L, and I believe there is a slight design change to the cooling galleries too...I had looked into doing this at some point too and was advised by the Pelican forum members that it wouldn't work... :( . However, if someone has done it, perhaps they can advise?


I'm just thinking of options as I have a complete S2 engine sitting around.
Author:  Prophead [ Thu Aug 16, 2018 6:13 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
I had very similar symptoms on my first 944, which had had the HG done yet the system was pressurizing. When the head was removed the gasket was perfect. The cause was that the head had not been skimmed properly allowing combustion gasses past the gasket and pressurizing the cooling system. It would start and run fine, even did over 100miles on a motorway run with apparently no issues, but once I stopped for any period or turned the car off then it would either pop a hose off or spew from the header tank. And the hoses where rock hard with the engine running.

After getting the head done properly and a new gasket the engine was great no long term damage done.

It is quite possible that you are seeing the symptoms rather than the cause.
Author:  infrasilver [ Mon Aug 20, 2018 2:53 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Pulled the spark plugs today and used a wooden skewer to dip in to each cylinder just to check for fluids, number 3 had a little coolant in it, showing around 1cm deep on the skewer. I turned the engine over and it fired all the water out like a jet, about 4m across the drive, so it seems the head will be coming off, just hope it is only the HG?
Author:  Prophead [ Mon Aug 20, 2018 6:28 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
infrasilver wrote:
Pulled the spark plugs today and used a wooden skewer to dip in to each cylinder just to check for fluids, number 3 had a little coolant in it, showing around 1cm deep on the skewer. I turned the engine over and it fired all the water out like a jet, about 4m across the drive, so it seems the head will be coming off, just hope it is only the HG?


Fingers crossed. Make sure the head is checked for flatness by a machine shop.

On the bright side, you now know that the rings aren't worn and are sealing fine otherwise that coolant would have been in your sump.
Author:  infrasilver [ Mon Aug 20, 2018 7:21 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
The head had been skimmed a few years ago but I didn't skim it when I rebuilt it last year as I didn't want to take much more off it with it already being done once before, I did check its condition and it all looked good.

I used the thicker head gasket at the time too but I can't find the correct one for skimmed heads now, the standard one is showing at 1.09mm but I can't find the thickness for the one I previously used?

The rings were new when I rebuilt the engine so have only done a couple of thousand miles.
Author:  Matt749 [ Tue Aug 21, 2018 1:46 pm ]
Post subject:  Re: 944S overheated, potential engine damage?
Sorry to hear the gasket hasn't sealed properly. From memory on the 8 valve head the standard gasket is 1.1mm and the thicker version is 1.4mm. Both types show in PET for the 8 valve so i guess they are also available for the S from OPC.

Good luck with it.
Page 1 of 1 All times are UTC
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/