9 replies to this topic

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Hi,

I bought a 25 a couple of months ago which had sat for a while but been put back on the road.

It was running really rough, so I put it in for a full tune up at a local garage who soon discovered it didn't have a thermostat in the housing. They fitted a new thermostat, and got it running lovely, albeit a bit underpowered for my liking!

I have only used it a handful of times since, and have noticed white smoke when pulling off, but nothing too concerning. But on Saturday, the first time I had been out in it in the warmer weather, it began rapidly overheating when in a queue for a matter of minutes, and pluming white smoke out on tickover and underload. I let it cool, and once driving again it calmed down.

I have not driven it since. I have checked under the oil cap which is relatively clean, and under the rad cap, which has a layer of brown grease type material on it, and the internals of the radiator look fairly dirty, with quite rusty water also noticable.

My first instinct is that the headgasket needs replacing along with a full overhaul of the cooling system.

What does everyone else think?

Its a 1984 998 A+.

Thanks,
Adam

[Alex_B]

Get a compression tester, whip all the plugs out and test each cylinder, that will give you a good idea as to the health of the head gasket :) 

[cal844]

Compression and leak down test too :)

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Thanks guys.

What sort of readings should I be expecting compression-wise?

[coopdog]

Sounds like the rad is full of crap, I'd be tempted to flush the system before messing around with headgaskets,

But a compression test is a good shout!!

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That's my first point of call, but what made me think gasket was the white smoke.

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Results of compression test as follows (all plugs out, throttle fully open, cranked until needle stopped)...

Cyl. 1- 190

Cyl. 2- 170

Cyl. 3- 180

Cyl. 4- 190

Does this point towards a leak between 2 & 3 or is that difference tolerable?

[Alex_B]

I personally wouldnt be too worried about that result however as it sounds like coolant is getting into the cylinder (white smoke) I would say there may be an issue, what did the plugs look like? were any plugs very clean looking? If you are getting coolant leaking into a cylinder it tends to steam clean that cylinder and you should see evidence of that on a plug 

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The plugs were all matching and nicely browned to be honest, couldn't see any differences.

[lsto]

Pop down to your local garage and ask if they can do a 'sniff test' on it. If they have the tools you can check if the gasket it blown. It uses a blue liquid which they draw the air through from the radiator, ie take the cap off and draw the air from the surface of the coolant. If there is any exhaust gas in the coolant, which if the gasket has blown there will be, the liquid will turn yellow. It sounds complicated but when you watch it then its simple. Tell the mechanic you'll give him a drink then its a simple yes or no answer.

Good luck