V8 saloon coolant circulation

[steve thomas]

I needed to remove the engine from my car recently for various reasons and have a question regarding coolant circulation. When I drained the radiator the coolant was clean and green from the antifreeze (surprisingly so I thought). On removal of the engine and subsequent spillage of coolant from the block, it was a very dirty brown colour. To me this suggests that the coolant has not been circulating and mixing since the last time I drained and re-filled the radiator several years ago. Potential causes could be a faulty thermostat, water pump not working, airlock etc. However, i would expect any of these to result in serious overheating which was not happening. The car warms up as expected and temp stays in the normal range, admittedly on generally short local trips.

Am I looking for problems that don’t exist (and I really don’t need any more) ? Or would those more knowledgeable agree that something is not right?
Thanks
Steve

[buckfield]

Hi, it might just be sediment laying in the block, if in doubt remove all core plugs and drain cocks and flood it with water from a hosepipe and prod with some firm wire around the cylinder jackets and let it run clear as I did this on my V8 and a lot of crud came out of the block but the engine wasn't overheating so maybe these engines can take a bit of silting up? other folks may no more than me tho. tony

[bobtills]

I've read somewhere that they tend to silt up badly towards the rear of the engine, and if this was the case you would perhaps expect the temperature gauge (situated at the front of the engine) to read 'normal'.

As you've got the engine out, it might be worth while taking it to someone who knows about this and has the kit to flush it properly - might be time & money well spent.

[classiclife]

However, I would expect any of these to result in serious overheating which was not happening. The car warms up as expected and temp stays in the normal range

Hello Steve,

Your observation in the quote is spot-on. If the thermostat remained closed or the pump was failing to circulate the water correctly then I would expect the car to overheat within a short period of time. Coolant cannot disperse generated heat unless it is being circulated and via the rad.

I agree with Syd that the brown colour you have witnessed is indeed the lowest level of water within the block, hence tainted with sediment. In addition you have to accept that there must be a degree of undisturbed water, the water pump cannot "draw" water it purely moves it. The further away the water is from the activity of the pump the more likely it will remain static. Following on from that, sediment within the block reduces the flow due to settling - hence the requirement to thoroughly flush the block through properly. This is generally achievable with an engine block in situ but not the best, however you say your engine is out at the moment and this will give you the optimum opportunity to clear 99% of the sludge and sediment.

Any core plugs that look suspect need to be replaced and it may well be the case that you swap the lot. Any or all is an additional help to clearing the block of debris. You will be surprised how much undisturbed muck over the decades has collected. The V8 saloon engine does slope very gently towards the back and this is where most of the sediment congregates which in turn reduces the cooling ability, in that section of the engine for obvious reasons.

I would not say you are looking for problems that do not exist, but you do need to be aware of the issue. In this case you are and in a position to go something about it.

Ensure you use a 50/50 blue AF mix, as this helps to stem accelerated waterway corrosion - especially with alloy heads. You mention green, hopefully this is a Monoethylene Glycol based product which is the correct chemical formula ??

Hope the above assists ??

Good luck.

Richard.

[John-B]

I have my doubts that green antifreeze is correct. When my engine was restored Phil Glennerster renewed it with blue A/F (Bluecol).
Halfords says "A general guide to antifreeze
Cars made after 1998 normally need antifreeze that uses silicate-free, organic acid technology (OAT). These types of antifreeze offer better corrosion protection so that parts don't need to be changed as often. [green or pink, I think.]

Cars made before 1998 usually need antifreeze that isn't OAT-based and that does contain silicate." (Blue)

[classiclife]

I agree John, that's why I thought it was worth a mention.

My personal choice for my classics is Granville Sub Zero Blue; it is a Monoethylene Glycol based antifreeze that does not contain nitrates, amines or phosphates. It also contains corrosion inhibitors suitable for aluminium engines along with alloy / iron combinations, such as the V8 engine.

Regards.

Richard.

[steve thomas]

Thank you all for the replies. I think I will order a set of core plugs, remove the old ones and give everything a good clean up and flush. I will certainly replace the antifreeze with the correct type.
Many thanks
Steve

[Petelang]

I always put some corrosion inhibitor from Morris oils in my vehicles. Its called Ankersol if I remember correctly and that turns Bluecol antifreeze a vivid almost florescent green. Great for tracing even the slightest leak as it shows up clearly and its got to be doing some good preventing corrosion and lubricating the pump innards.
Peter