Cooling system issue

[Viterbo]

I rebuilt and upgraded my 5K on the last months and to ensure proper cooling I upgraded my radiator.

I chose a Nissan Primera GT (SR20DE) radiator because the inlet and outlet are on the same sides as my standard radiator but the Nissan one is huge!

Made my way with the mounts and pipes but I'm having an issue while the engine is running.

I'm still using the stock expansion bottle and when I push the engine hard the bottle overfills and spills the exceeding amount.

I have 3 possible causes:

1 - Since the radiator is far bigger and takes a bigger volume of coolant, can it be expanding properly and the stock bottle is just too small?

2 - Maybe my radiator cap is faulty?

3 - Blown headgasket (unlikely since it only has 1000kms and no other headgasket related issues are present. No oil/water mixing, no overheating, nothing)

As said above the engine is not overheating in any circumstance, it just expands too much coolant.

 

Here's some pics:

 

 

 

 

[Big G]

You can blow a head gasket between water and exhaust and this pressurises the cooling system and forces the water out. It wont overheat until all the water is gone. Check at the radiator filler point for bubbles of air when the radiator cap is off and the engine is running.

[Viterbo]

18 minutes ago, Big G said:

You can blow a head gasket between water and exhaust and this pressurises the cooling system and forces the water out. It wont overheat until all the water is gone. Check at the radiator filler point for bubbles of air when the radiator cap is off and the engine is running.

 

 

Everything is fine, I bought this tool to help me bleed the system and after a few big bubbles came up (after the thermostat open) it stabilized and no more bubbles appeared

[Banjo]

Hi Viterbo,

                  Interesting issue, to which there must be a simple solution, but I can't quite put my finger on it as yet.

I did a similar modification, but I didn't use the Nissan radiator, as although it had the inlet & outlets in the right places, it was too big.

I used a Toyota Echo aluminium radiator, & the results were exceedingly good.  The Echo radiator, is very close to the original size of the K series radiator.

The aluminium radiators are so more efficient than the old brass ones, that my thermo-fan rarely comes on.  Usually, 4-5 minutes after I have stopped, & turned the engine off, after a "spirited" run.

I can imagine your engine maybe over cooling, if there was no thermostat fitted, but not overheating. 

Have you taken any measurements of coolant temperature around the engine ? 

Did the head gasket coolant holes line up OK, so the flow between block & head, was not impeded ?

Does this standard expansion bottle overflow water feel really hot ?

Have you simple tried a bigger vessel, in place of the existing plastic bottle ?

On the Echo radiator, I used, the overflow/expansion bottle, which is part of the radiator shroud. It was much smaller than the original K series, so I was initially concerned is might be too small. It was not an issue at all.

I look forward to your answers to my queries, so you can get to the bottom of this.

Pretty sure the answer is going to be simple.

Cheers Banjo.

 

 

Edited June 11, 2019 by Banjo

[Viterbo]

Didn't measure temps, I'm just guiding myself with the cluster temp gauge and the behaviour is exactly the same as before.

The headgasket I'm using is the same I was using before (well, not the same same...), everything lines up perfectly although some holes are blocked. Got to know a few weeks ago these holes are blocked to force the water to the back of the block?

It's not boiling water but it's very hot yes, once again, same as it always was.

Nope, haven't tried a bigger bottle yet.

 

My first attempt is to install a new radiator cap as this one has a few years and has seen some not so clean coolants...

[Banjo]

Hi Viterbo,

                  The blocked coolant holes at the front of the head gasket, are certainly designed to direct more flow to the rear of head, which has always run hotter than the front. I fixed this K Series issue up, but putting in an extra return path to the underside of the thermostat, from the rear of the head.

I would definitely check the radiator cap, & maybe take out the thermostat, & test it's opening in some hot water on the stove; carefully noting the temp, at which it cracks open.

I couldn't see from your pictures, whether you are using the original mechanical fan, or whether you have a thermofan. With a radiator that large, the coolant temp should be kept in range by just the "ram" effect of the air passing through it, whilst driving.  My thermo-fan rarely comes on, as I have an LED on the dash, that illuminates, when the fan comes on, if the temp, goes above 95 deg C.

Cheers Banjo

 

Edited June 11, 2019 by Banjo

[Viterbo]

My thermostat is brand new and (judging by the cluster) it's working as it should.

My car already has a thermo-fan from factory and I'm using it. Only comes on when the car is stopped.

 

Just went to check the part numbers for the standard Primera expansion tank and apparently the tank has a cap that opens at 1.4bar (besides being a lot bigger than mine). So the radiator uses a 0.9bar cap and the expansion tank uses a 1.4bar cap.

My expansion tank has no pressure cap, just a normal closing cap. 

Hmmm.....

[Banjo]

Can you explain to me why the Nissan Primera has two caps, (one for the radiator, & one for the expansion tank), & why the expansion tank cap would open at a higher pressure than the radiator ?  As the overflow, from the radiator, usually only goes to the expansion, or overflow tank, I can't see why it would need a a second cap, & why it would be at a higher pressure rating. 

As you are using the original K Series overflow bottle, which does not have a pressure cap, I can't see that being an issue, unless your existing radiator cap is faulty.

Cheers Banjo

Edited June 11, 2019 by Banjo

[Viterbo]

I can't explain it neither... That's just what I found through the part numbers.

After replacing my cap, if it doesn't solve the issue I might try reinstalling the standard radiator just to see the behaviour.

I really don't believe in headgasket issue because it did this since first start after rebuild (and the radiator was used since the first start). He keeps overflowing until he's "happy" with the amount of coolant it has and then works fine. But that means the radiator is not full (although it never overheats)...

[Banjo]

As you have been very careful filling the engine with coolant, we can assume there are no air locks inside the block or head.  Is this overflow of coolant, you are experiencing, happening when you are driving the car, or when stationary ?  What is the ambient temperature where you are located ?

I suggest that you disconnect the thermo-fan, so it can't switch on.

Remove the radiator cap, start the car, & let it run, in a stationary position, to allow the coolant to heat up.

Look down the radiator filler neck, & the coolant should be very still, until the coolant reaches the point where the thermostat, cracks open, at around 85-87 deg C.

When this point is reached,  little bubbles start to appear at the filler neck, & then the water starts to move & flow, as the thermostat opens further.

Quote

He keeps overflowing until he's "happy" with the amount of coolant it has and then works fine. But that means the radiator is not full (although it never overheats)...

"Not sure what you mean by " But that means the radiator is not full."

The radiator should always be full in a totally closed pressurised system.  As the coolant heats up & expands it increases in volume & pressure. That extra volume increases the pressure in the coolant system, & the radiator cap opens, & allows the excess coolant into the "expansion" tank. The coolant system & radiator still will be full of water.  When the engine cools down, the reverse happens, & the vacuum created within the coolant system, opens the second return valve in the radiator cap, & the coolant in the expansion tank, is sucked/drawn, back into the coolant system.  Most coolant overflow/expansion tanks have a mark on them showing max. This is usually about 2/3 or 3/4 of the capacity of the tank. This is when the coolant is cold. Therefore the free capacity of the expansion tank, is the volume provided for expansion overflow of the coolant.  It does not require a great volume. It is important, if you are using the K Series overflow bottle, that the tube on the bottom of the cap, is not missing. Unless the overflow line is below the level of coolant in the expansion tank, it cannot draw the coolant back into the engine.  That's why a lot of coolant / expansion tanks, have the overflow line connected at the bottom of the tank, so that it is always covered by coolant.

Cheers Banjo

 

 

Edited June 11, 2019 by Banjo

[Banjo]

I just noted this comment of yours . . . .

Quote

My first attempt is to install a new radiator cap as this one has a few years and has seen some not so clean coolants...

Is the radiator cap you are using, the one that came with the Pimera radiator, or are you referring to the one from your original K Series radiator ?

I'm starting to suspect, that your coolant system, is simply not pressurizing.

After the engine has been running for a while, but before the overflow starts, have you removed the radiator cap, by hand, & noticed that there is a "pressure release" ?

Cheers Banjo

 

Edited June 11, 2019 by Banjo

[Viterbo]

It's the K radiator cap that I'm using.

Now that you mention that maybe be the issue because I don't have trouble removing the cap even when fully heated. I really need to test with a new cap.

[Banjo]

Think we might be close to solving this.  There are lots of different radiator caps, & it's "pulling a long bow", to expect an early K Series radiator cap, would work perfectly with a later model Nissan Pimera.

Let us know what the results are.

Cheers Banjo 

[Viterbo]

I bet they're the same, but just to be sure I ordered one for the Primera

[Viterbo]

Just checked and the caps are the same. Same sizes, same pressure.

I remembered I had something around that I could try.

 

Not a genuine one but it's new and must work properly. Only difference is it opens at 1.3bar and not 0.9bar.