Have I just become a victim of porous block?

[MisterT]

My Griff 500 is a 94 pre-serp.

I've been having a minor issues controlling the running temperature the last few times I've taken the car out, I've checked all the usual points which seem in good order, correct coolant level, thermostat working, fans switching in OK, but still seems to run too hot.

I took it for a run today, after about 10 miles running down the A15 to Peterborough the car started to seriously overheat and even with cooling fans continuously running there was no drop in temp. As I was approaching the Werrington traffic island on the A15 the need to stop for a cool down was urgent and as I pulled into the Total service station the swirl pot cap started to blow off steam, and when I lifted the bonnet it was shooting out hot water as well!

I waited for the thing to cool down and topped up with water, soon after starting up again the same result and the hoses were rock hard, I've done a search on here and the symptoms described by Rob from V8 devt in a previous post about porous blocks seem to indicate the worst.

The oil is clean with no sign of water in it.

Two questions;
1 Does this sound like a porous block or could a head gasket failure cause these symptoms?
2 Is it possible to top hat liner a block that has already developed this fault?

TIA
Mike

[clive f]

I would have thought that a blowing head gasket would give you loads of steam coming out of the exhausts.
If you have been having problems with it, have you bled the system properly when topping up if you have lost a lot of water?
I had a similar problem with mine a while ago after a rebiuld, and found that the heater would not blow hot air, yet it was overheating, so had to put a hose pipe onto the heater pipes, as I had an airlock in the heater matrix, this solved the problem easily to my relief.

hope this helps.

clive

[GreenV8S]

Have you bled the radiator recently? Air in the rad can cause the sort of symptoms you're getting. So can a heavily silted or scaled up rad. If you're concerned that the engine may be blowing into the cooling system take the cap off the expansion tank and start the engine, if the engine is blowing into the coolant you will get lots of froth blown out when you rev it. You can also do an HC test on the coolant for a more scientific test. I'd check the basics though before assuming that your engine has died.

[MisterT]

Clive, following your post I've just checked the rad and heater. The rad was fine but the heater wasnt! I've flushed thro with a hose and now the system seems to be behaving itself and sitting at a steady temperature although at about 100 on the dash gauge, which is a bit hotter than I would like.

What mystfies me is that the coolant was changed last year march 2006 and the heater has worked since then, the car hasnt had much use since Oct 06 and i cant understand how an air lock could have formed?

Thanks Clive, your advice has worked wonders, I can now take advantage of the Ashbourne Motor Club track evening at Donington tomorrow that I am booked on.

I just hope the overheating earlier hasnt caused any sort of long term damage or brought on what I feared earlier ie a porous block!!!!

GreenV8S, no coolant thrown out with the cap off, I think a full cooling system overhaul is called for. thanks for your advice.

Mike

Edited by MisterT on Sunday 22 July 19:35