Expansion tank cap woes.

mcapinha said:

After my recent problem with the expansion tank filled with some kind of goo (http://www.landyzone.co.uk/lz/f10/expansion-tank-cap-full-gunk-158412.html), I decided to add a new tank cap to a order I had planned from Island 4x4.
The cap I received came in a Britpart bag and had no indication of it's manufacturer. It looks identic to my old cap with the exception that the valve (marked 140) is yellow in the Britpart one and red on my older cap.

So, I replaced my old cap with the new one and drove around 300km when the engine temperature started to rise just above 12 o-clock. After a while it started raising more quickly and I let go of the gas and drove slowly to the first service stop. Plugged my Hawkeye and read that the engine was over 100ºC and while idling the temperature started to raise once again (going over 12'o-clock and reading over 100ºC). Stopped the vehicle and very carefully took the cap off. Exchanged it with my older cap and drove without a single problem for the next 100km. Hawkeye plugged in all the way and the temperature of the engine never went above 95ºC.

So, which cap is at fault ? Was my old cap broken and masking a problem or is the new Britcrap cap the culprit ?

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wammers said:

Did you lose any coolant in this process?

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mcapinha said:

Yes and it looked like that some of it had come out through the cap's screw (and some had come out through the discharge pipe).

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mcapinha said:

Yes and it looked like that some of it had come out through the cap's screw (and some had come out through the discharge pipe).

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Datatek said:

Maybe it was just not screwed down tight, mine is very hard to turn the last 2 turns.

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wammers said:

Right that is what i needed to know. Cap is a simple unit that allows a certain pressure to build within the system and release excess pressure. 15 psi is the setting for your cap, each pound of pressure raises the boiling point of the coolant by 2 degrees F. So instead of boiling at 212 F it boils at 242 degrees F. If the cap is not sealed properly and there is no pressure or lets pressure off below 15 psi. Coolant will be vented and the temp will rise. I would say either you did not tighten your new cap down properly or it is duff. Also that your old cap is sound.

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john winsemius said:

read where a proper 50/50 mix of antifreeze and h2o will boil at 240-260 degrees f depending on altitude and 95-100c is within operating range of lr specs.
also on the range rover the thermostat is a electric operated not a mechanical operated

and with a new cap put a thin film of oil and the rubber seal will set it self easier when you tighten it and will go on harder when new

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mcapinha said:

Here's a pic of the new cap:

Looking carefully at it the second o-ring from the top seems twisted and I'm not surprised that it won't seal properly

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fett said:

usual britpart ****e then :doh:

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mcapinha said:

That's exactly where I was going when I started to write this thread. I toned it down a bit after having doubts about the original cap (which I'm now using without any problems).

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mcapinha said:

Well, will you agree that the Britpart logo usually favours the possibility of **** happening ?

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