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Have a question about the chargecooler resovoir

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I was looking at what I assume is the chargecooler resovoir and noticed that the clear plastic tube running out of it is dry inside. I started the engine and gave it a bit of a rev and did not notice any fluid run through the hose (does the engine need to be under load?). I tried to take the cap off to see if there is any fluid inside but when I loosen it and try to lift it, the cap will not come off. It wobbles and what not but will not lift off for the life of me. Anyone had this problem that could advise how I can get this cap off? Should I see some fluid in that clear tube? This tank is right next to the radiator head tank. Thanks!

Erik E.

1994 Esprit S4

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I think you are describing the pressure relief cap. If so then it is doing its job

correctly, the first turn should indeed make it loose but NOT removeable.

(imagine steam coming out of it, better coming out of the loose sides than

out of an open resovoir into your face!).

There are lugs still holding it there. they are supposed to. Push down on it and turn

it further and it will come off. this two stage removal is common to expansion caps.

Secondly, the clear hose. i think you descrbe the one that comes out of the caps

fitting?. If so this should be dry with no flow. This will only be wet if the pressure

cap releases any surplus water through it (eg if you fill the system right to the top

then when it gets hot and expands, the relief cap will reach the required pressure

and expel the surplus through this pipe and onto the road).

If i fill my chargecooler system to the top and go for a run, i would expect to see

water dripping from under the car as it finds it's level. Then when i check the level

it will be about 1" down from the cap where it will stay. If i filled it again, it would

just expel it again once it expanded.

Same with the engine coolant, two weeks ago i filled mine to the top by accident

as i could not see the MAX line in the bottle. It expanded and blew out the excess

and now it's sat at the correct level and stays there.

Be aware though, there are issues (head gasket, failed relief cap, failed rad or fans)

that will cause your car to expel its water through these caps, so unless you have

recently filled the system, this pipe dripping should at the very least call for an

inspection of the levels, the condition of the coolant etc


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Sounds about right to me Paul.

Actually the cap on my chargecooler tank is pretty difficult to get off. As Paul says, once loose push down hard and turn again...

The cap on the engine coolant header tank is not actually a pressure cap - it is a blank that will not blow under pressure. The system has a separate overflow bottle (the plastic one on the left hand side of the boot above the wheel arch) and it is this bottle that has the pressure cap.

I have no idea why Lotus choose this system - any one enlighten me?


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Guest esprit geoff
This is dropping down the list. I don't like being the only one giving advice

in case i'm talking a load of rot, so someone confirm my assumptions?

Or maybe he's cracked it?



Yes you are right - the clear pipe (well it's often a yellowy colour is an overflow pipe, and should be dry. It hangs right down under the engine etc. So nothing normally flows through it.


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I've discovered on my S4 that I can't get the chargecooler cap off until I've removed the main engine cooler cap. The latter fouls the former. You might want to try that way Erik.............when the engine is cold !!!!


Wing Commander Dibble DFC<br /><br />
North Midlands Esprit Group<br /><br />
NMEG "the formidable squadron"<br /><br />
"probably the most active Esprit group in the world" Andy Betts, Castle Combe May 2007

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