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[TheBoy]

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.

The heater will be bypassed via hbv if heating set to cold.

[TheBoy]

OK, stopped the engine. Dash gauge around 93 degrees.

Top hose hot.  Bottom hose from rad to stat is cold.

Either:
1) I have the worlds most effective rad
2) I have no circulation at all (or minimal) through rad - would the engine heating up cause the water to expand enough to get the hot water in top hose, possible a bit in the rad?

Can an expert say what will happen if I remove stat completely - could my new stat be faulty (and the original stat OK-ish, albeit drilled)?

[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.

The heater will be bypassed via hbv if heating set to cold.

Ok, never thought of that

[Matchless]

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?

Just double check the design of the thermostat, the wax capsule should face the heat source (engine) Im fairly certain there are designs with the spring on the opposite side to the capsule.
Im surprised that its only just opening the stat after an hour, seems a bit slow to warm up but then Im not familiar with diseasels.
Is there a vent in the thermostat plate or some other way that air can be purged from the stat?, they only work if 'wet', should clear any trapped air once it does open though.

How much sludge or muck have you seen in hoses, around the pump cavity etc? The waterways in an engine are fairly large so wouldnt tend to block up, radiators have much smaller passageways so clog up first and you think your old radiator was OK.

Does a diesel run hotter if injection is late (retarded), certainly makes petrol run very hot?

The old pump was OK....could it have been changed following an impellor failure and the bits are still in the water ways? I ask because it seems a common thread if you search for cooling probs on 5 series.

[Matchless]

I have a thermocouple type temp meter somewhere, we can slip the thermocouple under a hose joint to confirm the real water temp. This would confirm the gauge reading.

[Marks DTM Calib]

Does a diesel run hotter if injection is late (retarded), certainly makes petrol run very hot?

Apparantly yes, this is a technique used during warm up to get them upto temp quicker...not sure if this power plant uses this technique though...

[Martin_1962]

It is minimal circulation.

Try with no stat and see what happens.

[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?

Just double check the design of the thermostat, the wax capsule should face the heat source (engine) Im fairly certain there are designs with the spring on the opposite side to the capsule.
Im surprised that its only just opening the stat after an hour, seems a bit slow to warm up but then Im not familiar with diseasels.
Is there a vent in the thermostat plate or some other way that air can be purged from the stat?, they only work if 'wet', should clear any trapped air once it does open though.

How much sludge or muck have you seen in hoses, around the pump cavity etc? The waterways in an engine are fairly large so wouldnt tend to block up, radiators have much smaller passageways so clog up first and you think your old radiator was OK.

Does a diesel run hotter if injection is late (retarded), certainly makes petrol run very hot?

The old pump was OK....could it have been changed following an impellor failure and the bits are still in the water ways? I ask because it seems a common thread if you search for cooling probs on 5 series.

Sorry, it reached 90ish after about 10mins, maybe 15m.  After an hour, it was still 92.  Sorry if I was unclear....

[TheBoy]

How much sludge or muck have you seen in hoses, around the pump cavity etc? The waterways in an engine are fairly large so wouldnt tend to block up, radiators have much smaller passageways so clog up first and you think your old radiator was OK.

We found the old rad had a cold spot.  Also, it had signs of a repair. So I have put on a spanking new GM rad.

The hoses I've had off look nice a clear, just discoloured (brown) inside.  No gunge.

[TheBoy]

Just double check the design of the thermostat, the wax capsule should face the heat source (engine) Im fairly certain there are designs with the spring on the opposite side to the capsule.

New stat:


Old stat:


Both were fitted with spring towards engine.  It seems to me to be on the water inlet (comes from bottom rad hose).

?

[Kevin Wood]

Looks like the spring side of both of them is the capsule side so spring side towards engine is correct.

Sounds like it's a similar setup to the Rover K series where the thermostat is in the return from the rad. Bypass flow past the bottom of the 'stat is very important in this type of setup because the water from the radiator will be continually cooling the 'stat. Is it possible to see how the 'stat gets bypass flow (is it in a separate housing?) Could it be it comes from the HBV and it's blocked?

It would be interesting to run it without a stat in, just to see what happens.

Kevin

[sounds2k]

.... if it's easy-ish to ge at, why not turn the stat around anyway and see if that helps?

... and the "pope" method is to use gunk to flush with followed by a couple more normal ones afterwards. Not sure how any rubber seals might take that treatment though!

[TheBoy]

Going to attempt to run without stat as soon as I can work out how to get a seal (seal is normally on the stat).  Might just drill some more holes in old stat....

[TheBoy]

Just been for a spin with the drilled stat in, and the visco fan off.

Unfortunately, due to caravanners and old people, I couldn't really give it too much of a bootful.  Its the hardest I've driven it since I got it, and it stayed 93 - 95 through most of it, creeping up to 96 after giving it a bootload, then following grandad in his Audi at 15mph through town.

Still lost a load of coolant out of the cap though.



Any more ideas?

[TheBoy]

Possible, with the other problems, I've damaged all 3 caps?  I am reluctant to try MV6 cap, as that needs to get me to Drax tomorrow