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[JamesV6CDX]

I think, for what it's worth, you must have a blockage somewhere in the water channels.



I don't know about finding it though, without stripping the head.

My monies defo. on a blockage in the engine channels.

The only thing you could attempt, without dismantling, is some kind of mega strong flushing agent!! I read something over the other side once about the "pope" method.. and I've heard of people filling their coolant systems with petrol (from cold!) and running for a very short time... not sure I'd want to try it though!!!

[JamesV6CDX]

I think, for what it's worth, you must have a blockage somewhere in the water channels.



I don't know about finding it though, without stripping the head.

My monies defo. on a blockage in the engine channels.

The only thing you could attempt, without dismantling, is some kind of mega strong flushing agent!! I read something over the other side once about the "pope" method.. and I've heard of people filling their coolant systems with petrol (from cold!) and running for a very short time... not sure I'd want to try it though!!!

Also, Jamie, have you flushed that heater matrix yet? Regardless of the heat in the cabin, they can gunge up and restrict coolant flow - on some cars it has more of an affect than others. (Eg rovers don't seem to mind it - but Omegas (V6's anyway) run very hot with matrix a bit blocked)

I know it's a knuckle scraping job... but flush it from the top first, until it runs clear at the bottom... let the hose run for a good length of time... and then reverse flush from the bottom... you should see more crap coloured stuff come out when reverse flushing.....

[TheBoy]

I think, for what it's worth, you must have a blockage somewhere in the water channels.



I don't know about finding it though, without stripping the head.

My monies defo. on a blockage in the engine channels.

The only thing you could attempt, without dismantling, is some kind of mega strong flushing agent!! I read something over the other side once about the "pope" method.. and I've heard of people filling their coolant systems with petrol (from cold!) and running for a very short time... not sure I'd want to try it though!!!

Also, Jamie, have you flushed that heater matrix yet? Regardless of the heat in the cabin, they can gunge up and restrict coolant flow - on some cars it has more of an affect than others. (Eg rovers don't seem to mind it - but Omegas (V6's anyway) run very hot with matrix a bit blocked)

I know it's a knuckle scraping job... but flush it from the top first, until it runs clear at the bottom... let the hose run for a good length of time... and then reverse flush from the bottom... you should see more crap coloured stuff come out when reverse flushing.....

But if it was the heater matrix blocked, then the engine would cool when the coolant flow to matrix is stopped by hbv when set to cold.  Also, heater matrix doesn't appear to be in main coolant flow.

There is a large hose from the head to the top of rad.  There is another large hose from the bottom of rad to back to stat on the block, so should be a good flow from block, around engine via pump to head, to top rad hose, through rad, back to stat.

The original stat had holes drill in it, in effect bypassing it.

Is it possible to put the stat in wrong way round - would it fit, and would it affect it? I put stat in same way round as old one came out, though possible that was wrong??

[Auto Addict]

I think, for what it's worth, you must have a blockage somewhere in the water channels.



I don't know about finding it though, without stripping the head.

My monies defo. on a blockage in the engine channels.

The only thing you could attempt, without dismantling, is some kind of mega strong flushing agent!! I read something over the other side once about the "pope" method.. and I've heard of people filling their coolant systems with petrol (from cold!) and running for a very short time... not sure I'd want to try it though!!!

Also, Jamie, have you flushed that heater matrix yet? Regardless of the heat in the cabin, they can gunge up and restrict coolant flow - on some cars it has more of an affect than others. (Eg rovers don't seem to mind it - but Omegas (V6's anyway) run very hot with matrix a bit blocked)

I know it's a knuckle scraping job... but flush it from the top first, until it runs clear at the bottom... let the hose run for a good length of time... and then reverse flush from the bottom... you should see more crap coloured stuff come out when reverse flushing.....

But if it was the heater matrix blocked, then the engine would cool when the coolant flow to matrix is stopped by hbv when set to cold.  Also, heater matrix doesn't appear to be in main coolant flow.

There is a large hose from the head to the top of rad.  There is another large hose from the bottom of rad to back to stat on the block, so should be a good flow from block, around engine via pump to head, to top rad hose, through rad, back to stat.

The original stat had holes drill in it, in effect bypassing it.

Is it possible to put the stat in wrong way round - would it fit, and would it affect it? I put stat in same way round as old one came out, though possible that was wrong??

I know that you can put the stat in the wrong way on some cars, not sure about the Omega.

[TheBoy]

Thinking about the stat, and coolant flow.  I am wondering if the stat is fitted wrong way round...

It was fitted the same way round as old one.  Normally, they are fitted so the stat points towards the rad I believe?

However, this engine, the stat appears to be on the water inlet (?) from the bottom of the rad, rather than the normal outlet to the top of the rad?

Can anyone definatively tell me which way round it should go?

[Auto Addict]

Thinking about the stat, and coolant flow.  I am wondering if the stat is fitted wrong way round...

It was fitted the same way round as old one.  Normally, they are fitted so the stat points towards the rad I believe?

However, this engine, the stat appears to be on the water inlet (?) from the bottom of the rad, rather than the normal outlet to the top of the rad?

Can anyone definatively tell me which way round it should go?

Is it difficult to swop around? You've got nothing to lose by trying it the other way.

[TheBoy]

Thinking about the stat, and coolant flow.  I am wondering if the stat is fitted wrong way round...

It was fitted the same way round as old one.  Normally, they are fitted so the stat points towards the rad I believe?

However, this engine, the stat appears to be on the water inlet (?) from the bottom of the rad, rather than the normal outlet to the top of the rad?

Can anyone definatively tell me which way round it should go?

Is it difficult to swop around? You've got nothing to lose by trying it the other way.

A damn sight easier than v6 one

But I want to ensure it goes in the right way....

[TheBoy]

Looked up the stat they sold me, QH part QTH353, and it is the right part.  Quite a cold stat at 80 degrees.

[Mike Collins]

I may have missed this earlier in the discussion, but I have a vague memory of BMW coolant pumps having plastic impellors prone to failure. It is a BMW 6 ?

[TheBoy]

I may have missed this earlier in the discussion, but I have a vague memory of BMW coolant pumps having plastic impellors prone to failure. It is a BMW 6 ?

Yes it has, but pump already changed (nothing wrong with old one).  My first thoughts were pump as well, but Auto Addict and I changed that a couple of weeks ago.

[Kevin Wood]

Normally the side of a thermostat that faces the "hot" side of the cooling system is the side with the spring. I think this is the case whether it's in the flow or return radiator hose.

I would expect an engine to need to get up to 110-120 degrees before it blows the cap. The fact that it's doing it at such a low indicated temperature suggests one of the following:

1) Pressurisation is due to ingested air through HBV leak, etc. or head gasket, not boiling coolant.
2) The gauge is lying and the engine is getting hotter than it says.
3) Coolant flow is restricted causing boiling in some parts of the system while the overall temperature remains OK.
4) The cap opening pressure is too low.
5) The coolant antifreeze concentration is low.

I think most of the above have been eliminated. I'm starting to wonder about that additive in the coolant. If this is caked on somewhere it could be causing localised boiling. I read somewhere about flusing the cooling system with a degreaser such as Jizer or Gunk. Maybe more appropriate to cleaning out old oil after an oil cooler rupture but I'm wondering what would be best to shift whatever has contaminated this system?  

Kevin

[Marks DTM Calib]

Not cheap but, supposed to be very good.....

http://cgi.ebay.co.uk/FORTE-Cooling-System-Flush_W0QQitemZ330077166914QQihZ014QQcategoryZ25632QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

[Martin_1962]

I suggested no stat to see if it boiled without it.

I think some strong degunger is required, possibly even head off and flush out the head waterways, this is the hottest part and most likely to be the boiling.

Can't find anything on the internet about the M51 overheating, just comments about BMW engines of that era getting clogged by broken off plastic water pump blades.

Can you tell which direction the water flow is?

[TheBoy]

OK, double checked stat.  Spring faces engine, same as shown in TIS, and same as M_DTM's advice.

It has been idling on the drive now for about an hour, and is running at 92.  Top corner of rad is hot (where pipe from top of engine meets rad), rest of rad is cold, slowly warming up from that corner. How quickly should the rad heat up once stat supposedly open?

[nixoro]

Just a suggestion but could a partially blocked heater matrix cause these problems :-/

You say water is running through fine but could it be corroded enough to cause heating issues.