Header Tank

[wohlmeyer]

Sometimes it is the really simple stuff that kicks my butt on this car.  So hear is a simple question and I would like more than a yes or no answer if possible.  Is it possible to overfill the white bottle header tank resulting in coolant leaking past the cap?  If so how full do you make it?  There are no marks on the tank...

 

Thanks

 

Bill

[Sparky]

Generally, the system will find it's own level

Whoops, premature text injection!

The cap will vent excess pressure allowing the system to find it's level. I tend to aim for, or just above, the tank seam. Of course you may have another issue causing this, if you don't feel you're overfillibg.

[CarBuff]

The plastic header tank on the rear engine wall should remain full (or practically full, less than an inch down from the top of the neck) when cold.

 

The plastic overflow bottle in the left-rear trunk (which, unlike many newer cars, is pressurized) will vary in coolant level. On a fully-bled cooling system, filling it more than half-way when cold (where the seam is) will result in the excess escaping through the top tube when the engine is fully warm.

 

The tricky thing is, often the overflow bottle gets a scummy COATING inside, that makes it look as if it has coolant inside, when it doesn't.

 

 

^^^ So, that's my wordy explanation of "the system will find it's own level"     

[sailorbob]

When the engine is fully cold the header tank should be completely full with a small amount of coolant in the expansion tank.

 

EDIT: Beaten to the answer

Edited June 24, 2014 by sailorbob

[CarBuff]

When the engine is fully cold the header tank should be completely full with a small amount of coolant in the expansion tank.

 

EDIT: Beaten to the answer

You weren't wordy enough Bob.

[Vulcan Grey]

On my car the pressure cap, on the plastic overflow tank, wasn't holding the normal 15psi, so it was venting coolant onto the ground behind the rear tire at ~10psi.  I lost a gallon of coolant on the track, and blew the head gasket.

 

Pressure check your system.

 

On the S4s the overflow bottle has a blanking cap, not a pressure cap, and the main header tank has a pressure cap.  So the overflow bottle will overflow onto the ground when it gets full...  SO don't fill it all the way, fill it half way.

 

On the earlier SE with the metal header tank, the header had a blanking cap, and the overflow had a pressure cap.

[Alex Carter]

Is there another option for a header tank I'm bored of the off white discoloured tank it looks Crap I either need a new one or a stainless or alloy one any input it's for a v8

[wohlmeyer]

Thanks for all the detailed information and replies.  Sorry about the simplicity of my question but I had my engine rebuilt 10K miles ago and I dont want to do it again any time soon so I am always paranoid about anything having to do with the cooling system on my car. 

Is there another option for a header tank I'm bored of the off white discoloured tank it looks Crap I either need a new one or a stainless or alloy one any input it's for a v8

Alex, you can get a new white bottle header tank from SJ sports cars, if you want a stainless steel one, lotus pbc has them but they are expensive.

[Alex Carter]

Pbc?

[Bibs]

Lotus Prepared By Cladius, it's an indy in the USA. 

[Alex Carter]

Ah thanks bibs I've emailed bailey they seem to list a stainless 205 replacement but no reply yet , also asked what happens to the water level sensor there are two holes in their product one is the pressurised cap and the other open ? Can't see what the point would be of transferring my old creamy cap with water sensor that would look shit

[Mike6]

^{My header tank was leaking so purchased an alloy one from SJs. Bit of a pig to get the old one out and fit the new one but literally just finished the job. Replenished the water and bled system and then sat back until it reached operating temperature. No problem until I noticed a bit of water escaping from around the overflow pipe under the pressure cap which then has a pipe round to the plastic secondary tank. Let it cool down and then noticed the overflow connector into the tank wasnt very tight and water could seep around the edge. It just seems to be lightly riveted in place}

 

^{Not sure if this will pose a problem and certainly dont want to strip down again. Took the car for a run and doesnt seem to have overheated so water must have found its correct level. This however begs the question of how necesary is it for the secondary tank if it merely collects overflow water and then in due course discharges under the car. Couldnt the overflow pipe go direct from the header tank to somewhere under the car.}

[Alex Carter]

Yes its seems a bit pointless just vent it to air looks like a better option

[dodge1979]

If I remember rightly the overflow tank is there so the system can draw coolant back into the header tank as it cools and pressure drops as required..keeping it topped up correctly

[Mike6]

Sounds plausible but not sure how coolant would find its way back up to the header tank when the pressure spring would have closed off any route back as it cools. 

[fjmuurling]

The pressure cap has two concentric valves. The outer is for venting to the outside, the smaller one in the center opens inward when the coolant is being drawn back into the headertank and causing underpressure in the cooling system.

[Mike6]

thank you. Interesting set up. As i have a slight leak here on new tank will have to check levels more regularly. Currently just not prepared to strip down again and get a replacement header tank.

[Roy Lewington]

I also had a leak on the overflow pipe from my SJS Alloy header tank.  It was threaded so screwded in but bearing in mind the thickness of the ally it didn't seal.  I refitted it with liquid metal------no leaks now.  Roy.

[Alex Carter]

Ordered a new one from sj odd how the level sender is nearly twice the price of the blummin tank lol

[Mike6]

Thanks Roy. Mine wasnt screwed in but the metal was turned over to grip the tank. It just pulled out  so I superglued it back - will add a bit of ligued metal. Still unsure about the concentric arrangement. SJ supplied me with a pressure cap for the new tank. It looked bog standard ie either open or closed. Checked the pressure cap on the secondary plastic tank and that had the arrangement mentioned above. Still not sure how water can be drawn back from the secondary tank if the valve on the header tank has closed - if the header tank pressure cap is open it will be passing pressure and water into the secondary tank. If its closed nothing is going to get back. Not sure I would want it to either. Drained the secondary tank and the water was horrible.

[Neil Potter]

Same problem with the sj alloy tank threaded overflow pipe. Used blue loctite to seal, all good.

[ragingfool35]

I made this combined tank and catch some flak about it.  works fine so far though

 

header tank assy 9 tri drawing.PDF

[mdw]

 Still not sure how water can be drawn back from the secondary tank if the valve on the header tank has closed - if the header tank pressure cap is open it will be passing pressure and water into the secondary tank. If its closed nothing is going to get back. Not sure I would want it to either. Drained the secondary tank and the water was horrible.

If its like mine an  88 the header tank has just a plain cap with no pressure spring/valve so the coolant can be drawn back in.  The 2nd tank ( expansion)  behind the l/h wheel arch has the pressure cap that vents to the ground.  Mine is always full at the header and 2/3rd full in the secondary plastic tank in the wheel arch.  

 

Just checked the parts list and it shows as described a blanking cap on the header and pressure cap on the expansion tank.

 

Chuck some descailer and some gravel in the expansion tank shake it about  a bit and it will clean it up. Cap the ends off before you shake though !!!!

[Mike6]

Malcolm

 

Thats interesting mine is an 88 and has a standard open/close spring on the header and another  pressure cap on the secondary tank with some sort of bypass valve incorporated. I wonder if there is a difference between the na and the turbo. 

[mdw]

I am pretty sure from the parts list view they' are the same. Infact. They have. A big drawing top of the page showing it not just parts numbers.