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Water guzzling V8

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Right just finished putting 4.2 in the 90.

The engine was fine before but has been sitting about a lot for the last year or so waiting for me to finish connecting it up

Drove 70 miles ( at mostly 60 - 70 mph ) and the cooling system lost 3 litres of coolant. Now the expansion tank might have been overfilled to start with but it took 1.5 - 2 litres just to fill where the radiator had emptied to ( i.e. I put 2 litres in and the expansion tank was still empty).

I don't have any white smoke ( that I can see ).

0-40 power fine 40-70 power lacking, (the auto box was kicking down on even slight hills and wasn't keen on accelerating regards of throttle position, tbh this could be anything and squirting the engine is now very close to the top of my to do list )

A chemical test for exhaust gasses shows negative.

The plugs don't look overly steam cleaned. ( two plugs are slightly clean on the vertical part of the contact )

The overflow tank cap is hissing when the engine is warm ( failed cap or over pressurisation I don't know )

Oil near filler cap is slightly greyish but this may be from condensation from sitting around.

If the cap is off during tick over coolant overflows from the tank and then the second you turn the engine off it all gurgles away into the radiator. I think the air builds up in the top of the radiator as if I remove the blanking plug from the rad on the top left I can see the water level is low before it runs back in from the rest of the system.

So my plan is to chuck a bottle of k-seal in and hope for the best. If anyone wants to yell "NOOOOOO don't do it !!! " now would be a good time. :lol:

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Morning D

It really depends as to if the system is not as it should be - ie a fault somewhere a leak in the system, a seal not 100% a header tank cap etc etc or if you have internal engine problems.

The key can often be to see if the system is presuring itself, thios is normally most noticeable with the top hose looking as though the incredible hulk is trying to blow it up, like a ballon, so before you do anything check and recheck the system.

Check the hoses are all on correctly where they should be and the systenm is flowing in the right directions with no blockages or obstructions.

Ensure that the system is FULLY Bled and there is no air in there, again how have you got the header tank connected, you should reaaly have a hose from the base of the header tnak going into the bottom radiaitor hose, a top hose to engine from rad, and a bottom hoses from engine to rad, a bleed screw on the rad and another maybe on the rail over the rover cover, and then either connected to the heater unit or a connector allowing the 2x heater pipes to join up, then the 2x hoses from the plenum heater one to the inlet one to the radiaor, I think that its from memory :)

Fill the system engine off, this also is where the rad and rocker bled screws work well, open and let the air out, replace bungs but not header cap

Start and then run at tickover, header cap off, run up until the themostat pops open top up and then top up about 3/4s of the header which is more than you need, sqeeze the top hose to help air out, replace cap and go for short dive, check for leaks anywhere !

Remove cap carefully with engine switched off after it has cooled a bit unscrew cap very carefully as it can pump out very hot water all over you :ph34r: and then see the level, maybe top up again. Also lastly are you sure the thermostst isn't sticking ?....I'd replace it anyway

Or ring me if you wnat to chat



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Thermostat already replaced, plumbing looks correct. I have the header tank feeding the bottom pipe and a T-piece in the small top pipe back to it so it is the highest point in the system. Getting new rad cap and gave the system another bleed but it's water drinking ability seemed to be rapidly increasing so in with the snake oil. Gave it a quick run and so far seems better post snake oil ( K -seal )

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  • 4 weeks later...

Okay new theory. I think my temp gauge is lying to me.

Now with mega squirt looks like the temp spikes on hard acceleration. Megasquirt reading sits at 95 and then I put my foot down and it's rapidly up to 105.

Ease of and it comes back to 95

The temp gauge on the dash doesn't move above normal.

So I think I'm boiling the water out of the cooling system.

So therefore I think I have an overheat problem.

The fan doesn't have a cowl which probably isn't helping but I would have thought at 60 mph the air flow through the rad would be pretty good.

Any suggestions for the next move ?

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Stat is new and genuine ( not that that means it works ). Rad is new ( that should work ) . The top pipe goes hot at 95 and then it pops back down to 92.

Cap is new and some rubbish halfords part.

But I think the overheat problem has been there since I put the engine in hiding behind the now incorrectly reading temp sensor gauge.

I can take the stat and and go for a run but for arguments sake lets say it still runs hot, what should I try next ?

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Right which way round should the heater pipes go on a V8 converted 90 ? and does it matter ?

For the sake of testing the problem link the two pipes together and see what effect it has. As to which way there is and in and an out but it does matter if you get it wrong too much :) Similarly remove the thermosta completely and try, not good long term but again for tersting it will be OK :)

Are you sure the heater matrix is clear ?


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no I'm not sure the heater matrix is clear. The old thermostat was open when I removed it ( did it with the engine warm to make bolts easier ) and it was open correctly when it came out. So I think the old one was a good un.

Where does one get a "laser" thermometer ? Although seeing as it mainly temp spikes under heavy load I might have to be a bit swift with getting the bonnet open and the laser gun out. :-)

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