Porsche Enthusiasts Club Forum

I have a confusing problem on a 1985 928 S2. Its been off the road for about 10 months. A quick spin revealed lumpy running and very down on power, felt like running on 7 or maybe 6 cylinders. Thought a bit of a run would clear it so booked in for MOT and on way took it on motorway, still no improvement. At MOT noticed a small coolant leak (no overheating though), car went in for emissions test when white smoke started billowing from exhaust. On way home, more white smoke, stalling, temp gauge a little high but not near red.

Presumed head gasket so topped up coolant, ran engine but no blow back through expansion tank and no further loss in coolant. Oil has slight evidence of water, oil header (where you put the oil in) is coated in thin layer of light creamy yuk. Interestingly, if I put the expansion cap on whilst running it stalls. If I run with it on (very difficult) the top radiator hose compresses almost flat indicating a significant vacuum.

Compression test (when cold) revealed 145, 155, 150, 165 front to back left side as you look and 140 to 145 on the right side. There is nothing absolutely conclusive for head gasket failure, has anyone had similar problems or any advice would be helpful
Many Thanks
Mike Dowie

Hi Mike

Sorry , but it does sound like head gasket to me

I don`t know where you are in the country, but if near me , pop in and I will run a Snap-On block test for you (for free), or find a local garage with the same tester and ask them to run a test....it should only cost you a few pounds....and it will show a blown head gasket or a cracked head or a cracked block (extremely rare)

All the best Brett

Hi and welcome Mike.

Brett is dead right, get the block test done. If you need to buy one let us know, but you're going to have to take the head off it to find out how much damage has been done. I suspect the head could have gone because of a blockage in the cooling system, so don't think that the head gasket will cure everything. you will need to flush the coolant. Please let us know how you get on, are you going to diy the head yourself or put it in a garage? Where in the country are you?

Thanks for the reply guys and the offer Brett but I'm in Livingston (central Scotland) so probably a bit too far. The car is undrivable really and I have no access to a trailer. I'm hoping to give it a go myself, not decided to do engine out or in yet, (I have a local Porsche mechanic who is a member of the club to offer advice). At the moment I want to make absolutely certain its head gasket so I'll give this snap on test a try, I presume this is available from snap-on? It sound like I've a few problems, coolant blockage, poor running problem - electrical maybe? I've not had much luck with this car, I've had it a year now and only managed to run it for about a month or so and its been off the road with one thing after the other, this is my first Porsche, are they normally this unreliable?

You're a couple of mile from me. I've sent you a PM.

Hi

This is the same as you would get from the local Snap-On van.... >>> http://cgi.ebay.co.uk/UNIVERSAL-BLOCK-T ... _Equipment

If you get one, let me know and I will give you my number so I can explain how to use it etc....

All the best Brett

mmm its not straightforward is it.!
White smoke from the exhaust definitely means you are getting water into one or more of the bores (presumably on one bank yes?)
But.. the temperature is not high and you are not losing a lot of water by the sounds of it most is leaking out somewhere.

Have you removed the spark plugs and checked the colour and surface ? it should tell you which bores are being effected at least.

I suspect that you may have the beginnings of a head gasket leak from coolant system to bore somewhere and the high compression gasses are being forced into your coolant system which has made a hose or connector leak .

What I don't understand is why the engine is cutting out when you put the expansion cap on ? Even if the higher coolant system pressure was forcing water into a couple of bores it shouldn't stop the engine. hell you should be able to remove 2-3 spark leads and the damn thing should still run ?

Actually that has just given me an idea. If you run the engine and one by one pull the spark plug leads off and back on again with insulated pliers you'll at least find the bores that are not working properly which will narrow your search

Lee, never noticed you were in Lanark, just down the road, excellent! But what’s a PM? New to all this forum stuff.

Peanut – I think you are right, its not straight forward, I’m not loosing any coolant (although I did when I had a small hose leak but how much leaked and how much went into the oil?? I don’t know) and remember I’m not getting blow back into the expansion tank, if it was a water jacket to cylinder leak the coolant system would be pressurised but it doesn’t appear to be. I thought the vacuum in the coolant was a blockage behind the water pump (in the flow cycle that is), which Lee thought of as well.

However, the fact that the engine cuts out when I put the expansion cap on suggests a link between the coolant system and the cylinders (I think), and if it is, surely there cant be anything else that could generate more pressure than the explosion in the cylinder to counteract it to cause a stall????

I have also checked all the plugs and a couple were slightly worse but this didn’t correspond with the compression test and none of the plugs looked great to be honest, not a uniform nice light brown covering, more black contacts with patchy/blotchy insulation.

I think its good advice to get this snap on test, I hope it will at least give me some conclusive evidence, at the moment I have conflicting evidence, which its why it bloody confusing.

Many thanks guys

PM ( Private Message ) - top left there should be a sign saying 1 new message! Next to the log out tag. It's like e-mails inside the forum.

I've only had mine 6 months and I deliberately steered clear of a low mileage little used one, I wanted one which had been driven. Apart from a bearing on the clutch shaft and a hopefully temporary problem with my air con it's been fine and if I'm perfectly honest it's driving better the more I use it and it does get driven not pootled around.

Whatever it is I hope you get it sorted and actually get to drive it when it's running properly and enjoy it.

Car now fixed!! I’ve had many suggestions as to what this could be and most have been doom and gloom, including my own thoughts. I had neglected to mention that I had changed the main ‘O’ ring on thermostat housing about 5 months ago. I was adamant I had put it all back correctly but what I had done was to put the crankcase breather hose onto one end of a switch that sits underneath the cross member (the other hose comes from the thermostat housing). And the hose that should have gone onto the switch I put into the top of the plenum. Oh dear, that means the hose going into the plenum came from expansion tank and when this switch thing opened it let water into the bottom of the inlet, just below the throttle. So hence the negative pressure in the coolant and the white smoke suggesting a head gasket.

I feel such a plum but the route of the hoses are not initially clear and it needed a friend to help me realise my own mistake. Thanks to all who posted advice.

Mike

well done Mike for finding the problem and sorting it. How frustrating. It certainly wasn't straightfoeward was it !

Good to get feedback on your solution as its bound to help someone else some day.

Great news Mike. Glad it's all worked out, I've been planning on coming over to help take the head off like you said. Just not had time lately. Having said that, when do we get to see her, I've never met another 928 on the road round here.

Cheers Lee, not on the road yet, needs some welding for MOT, bit of rust on the NS sill. Probably be a wee while yet, I've got a Mk1 MR2 that I'm getting ready for sale so I can concentrate my time and funds on the 928. Would be good to meet up at some point, will let you know progress.

Mike

If you're not busy on the 6th of October, I can pick you up and take you over to the meeting in Bo'Ness if you want? I hope to have the cam covers and inlet manifold back on mine by then.