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Radiator reservoir leaking


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The radiator reservoir is leaking at the bottom but only when engine is running. I was told the whole thing needed replacing. Also there is a sensor at the bottom. Can it be tightened up or does it leak thru the sensor?

If it's the sensor, why not replace it only??


Seems suspicious to me.



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Sorry to tell you this (or to add to it), but it is a "replace". They usually crack at the neck, but they can crack almost anywhere. There is no fix that is worth doing. Take a close look at the overflow tank as well, because now may be the time to do that. Especially look at the nipples on the return.

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The plastic tank is not under pressure. I lost a filler cap last year and didn't lose fluids.


I thought the plastic fitting may have come loose. It's semi visible and thought it could be turned to tighten. It looks like the pipe fitting points down so orienting hose would not be an issue.


Truck is going in for door fix so I'll get a second opinion.


Is a tank from EBAY going to work? It would not come with a sensor. Price was less than 150$ but from Dealer over 400$ with sensor.


I'm wondering if the sensor is or could be an issue? Are they prone to leaking?


Where is the overflow tank. My problem is with the plastic tank I top up fluids with.

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Maybe my expansion tank is different. But, it is definitely under pressure when the truck is up to temp on the passenger side of it anyways. It is a pressure cap and is the highest point of the system. With that being said, I would replace the tank and be done with it if it was my truck. Cheap insurance at less than $150 and a little time. Jeremy

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I'm with the pressurized crowd. My Volvo owners manual says :

Coolant Level Check
DO NOT remove the cap to the surge tank while
the engine and radiator are still hot and under
pressure. Scalding fluid and/or steam may be
blown out under pressure if the cap is taken off
too soon.

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Here is a better explanation from Google. I am not nearly as well spoken. LOL


While our coolant gives us some wiggle room for running our engine, warmer weather may prove to be an issue. This is where the “pressure” of our cooling system comes into play. When you increase the pressure on a liquid, you raise its boiling point. Our coolant’s boiling temperature of 223° F (106° C) is when it is under 1 psi, which is why most cooling systems are designed to operate at 15 or 18 psi.

As the coolant heats up, it begins to expand and create additional pressure. By allowing that pressure to increase, the boiling point of the coolant is increased to around 257° F (125° C) at 15 psi. This gives us better performance from our cooling system as it can absorb additional heat from the engine without boiling.

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Apparently you are talking about what is called a "header tank" or swirl pot which is different from an overflow tank which is used to keep the circuit bleed during expansion (heating) and contraction (cooling)

Stekay, I only have one plastic "tank", of any sort, attached to my radiator. It is also the only filler cap in the system.

The internet calls it a "Volvo Truck Expansion Tank Assembly 20519037"

Looks kinda like this:


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1 cap only, the leak is underneath. A white or yellowed plastic fitting into which I guess a sensor fastens into then a hose nipple below that. Before I start throwing more money down the drain, I want to see where the leak is coming from. Tank by itself is about 150$ on EBAY and over 400$ from a dealer with the sensor included.


Or something may be loose, lots of divots out of the road from Victoria to Southern Florida.


I-10 thru Louisiana was pretty good and so is Florida.


My thermostat rarely goes above 190 f

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Roger - see those two small hoses that enter the top of the tank? Take a careful look at those nipples they attach to with the weird Volvo clamps. Those fittings are often the source of "a problem". Typically the nipple drys out and pieces break off. You can get by for awhile "mcgivering" it....but in the end you will have to replace the tank. Make sure you have no issue there - if you do, then along with the other issue then you should replace the tank. Also, examine the actual radiator closely along the top where the neck is.....you may have hairline cracks there, and an actual leak......look carefully. These are both common problems. And not just in Volvo's.

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