Water temperature fluctuations
Discussion
Well since I put it back together there have been some obvious temperature fluctuations - for example it jumps up 5-10 degrees after a bit of caning then drops down after.
I got the laser thermometer out just now and it seems to be reading a bit high - probably 10 degrees high, so maybe I just need to calibrate the gauge with a resistor to make it look less worrying ;^)
It doesn't seem to be chucking out loads of water so that's a good thing.
I got the laser thermometer out just now and it seems to be reading a bit high - probably 10 degrees high, so maybe I just need to calibrate the gauge with a resistor to make it look less worrying ;^)
It doesn't seem to be chucking out loads of water so that's a good thing.
KKson said:
... A quick spanking and needle goes up 20 degrees to 100C then drive it steady and back down to 80C.
Doesn't sound right to me - best radiator cooling is when you are driving - in theory at least. Should only get warmer when stood still.So something is restricting cooling, either air flow through rad, or water flow through rad....
I've had a few weird things on cars over the years -
Leaking head gasket allows bubbles into cooling system. Sometimes hot, sometimes not.
Partly blocked radiator.
Faulty thermostat.
Air bubbles under thermostat (Triumph L6 engine) - weird - never did find out where they came from, but small hole drilled in thermostat
fixed it completely.
Blocked heater core - Ford Cortina was designed so that hot water always flowed through heater core, when blocked it caused choke mechanism to drop back in when engine hot, and caused other weird overheat problems.... air bubbles ?
I guess on wedge, it may also be some strange airflow issue ??
Yeah, just some ideas to consider.
The temperature should be around 90 once up to temp...And should drop slightly if using motorways...On a couple of occasions mine has blipped up a little when i accidentally went a few miles an hour over the speed limit...
As said before with the air intake hose that i put up to the filter from the nosecone i actually see a significant drop on high speed..Over 10 degrees...
Maybe jack the front up..Remove the swan neck cap..Burp the hoses and throw a bit more water in there..If you have filled the system too quickly then you will most certainly have air in there....
As said before with the air intake hose that i put up to the filter from the nosecone i actually see a significant drop on high speed..Over 10 degrees...
Maybe jack the front up..Remove the swan neck cap..Burp the hoses and throw a bit more water in there..If you have filled the system too quickly then you will most certainly have air in there....
Both my cars do the temperature gauge fluctuation thing; seems normal to me. I can log engine temperature on megasquirt on the 350i, as measured by the sensor feeding the ECU, and I do not see such large fluctations on that sensor output.
It does puzzle me; I wonder if the temperature of each bank of the V8 is different, or if the gauge sensor is located in an area of poor coolant system flow. The engines don't boil even when the gauge hits 110 DegC, so another possibility is that the gauge/sender is not accurate. Certainly the calibration curve of the ECU sensor is pretty flat at higher temperatures so maybe the gauge sensor is not very sensitive/accurate at higher temperatures.
It does puzzle me; I wonder if the temperature of each bank of the V8 is different, or if the gauge sensor is located in an area of poor coolant system flow. The engines don't boil even when the gauge hits 110 DegC, so another possibility is that the gauge/sender is not accurate. Certainly the calibration curve of the ECU sensor is pretty flat at higher temperatures so maybe the gauge sensor is not very sensitive/accurate at higher temperatures.
If the gauge is not compatible with the sender, the reading will either be excessive or insufficient. Using the sender that gives the excessive reading, by the use of resistors, it can be lowered to match the maximum of the gauge reading, hence calibrating the two components. I did this on my Wedge and the reading is steady and accurate.
Tony. TCB.
Tony. TCB.
If it's just the gauge, then there's more ideas....
I notice on my 2.8, the SW gauges don't have any voltage regulator, so they do vary a little bit by voltage (idle vs drive), but not that much.
I know that the 'classic' style Smiths gauges are simple 'hot wire', so they will vary quite a lot without a functioning voltage regulator.
Plus of course, there are the old favourites of dodgy earth returns and wiring issues, senders etc....
For example, if TVR wired the same earth wire for gauge lights and gauge return, the current flow to bulbs can add voltage changes at the gauges.
I know later cars had different gauges (VDO, SW, Smiths) so each type may not behave the same, but may be related.
I notice on my 2.8, the SW gauges don't have any voltage regulator, so they do vary a little bit by voltage (idle vs drive), but not that much.
I know that the 'classic' style Smiths gauges are simple 'hot wire', so they will vary quite a lot without a functioning voltage regulator.
Plus of course, there are the old favourites of dodgy earth returns and wiring issues, senders etc....
For example, if TVR wired the same earth wire for gauge lights and gauge return, the current flow to bulbs can add voltage changes at the gauges.
I know later cars had different gauges (VDO, SW, Smiths) so each type may not behave the same, but may be related.
So the cause has revealed itself at BBWF when the engine wouldn't turn over at Topcats. It was water in No 1 cylinder which hydraulically locked the engine.
Obviously the head gasket is knackered on the LHS (the side I assumed was OK) and the cylinder slowly fills up with water when you stop the engine.
I've started work on it tonight and have got the blower off, so out of interest I did a compression test on No 1 and No 2, and really you can't tell the difference. So I would still be none the wiser if the fault hadn't cropped up in another guise.
I'll be making another 4 copper exhaust gaskets to complete the set - this side is paramount to get right as the bolts are impossible to get to once the blower is back on. The copper gaskets are great - reusable infinite times - and make a good seal.
Obviously the head gasket is knackered on the LHS (the side I assumed was OK) and the cylinder slowly fills up with water when you stop the engine.
I've started work on it tonight and have got the blower off, so out of interest I did a compression test on No 1 and No 2, and really you can't tell the difference. So I would still be none the wiser if the fault hadn't cropped up in another guise.
I'll be making another 4 copper exhaust gaskets to complete the set - this side is paramount to get right as the bolts are impossible to get to once the blower is back on. The copper gaskets are great - reusable infinite times - and make a good seal.
adam quantrill said:
Here's the culprit...
Last time around this side wasn't giving a problem, which is why I didn't change it, also it would have given me almost double the work. Still this time around both sides have been renewed (albeit a couple of weeks apart).
Ahhhh but while you were thinking everything was okay it was quietly being a bastid...Did you sort out the starting issue?Last time around this side wasn't giving a problem, which is why I didn't change it, also it would have given me almost double the work. Still this time around both sides have been renewed (albeit a couple of weeks apart).
When the cylinder filled up with water after sitting there a while it hydraulically locked the piston, so it won't turn over. At Topcats it was pointing downhill which led to more water at the front of the engine which probably made it worse.
Yeah this should prevent No. 1 cylinder filling up... I would hope ;^)
Yeah this should prevent No. 1 cylinder filling up... I would hope ;^)
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