Temperature Sensor

[Jim the Box]

I have a TM temp sensor on my V6, it normally runs about 78'c, I tend to glance at it at fairly regular intervals, returning home from mull yesterday, the gauge crept up to 80'c then to about 85'c when I finally reached home, the engine was not hot enough to bring on the scavenger fans however it's fairly flat around my home, and if any-thing the van was wind assisted, I was really surprised about the increase in temp. Checked today, coolant level is normal, no visible leaks, should I be concerned?

[haydn callow]

What temp gauge have you fitted and where have you placed the sensor.......I have a V6 with a sensor on each rocker cover.....normally runs around 72C and I also have a sensor within the top hose which always reads within 2c of the the other gauge.

[Jim the Box]

Think it's a Tm2 Haydn, it's mounted right at the front of the engine near the top of the block (there was a unused threaded hole on mine) so it is mounted equidistant between the 2 heads. It's sat at 78'c all winter during normal running, it was 13'c yesterday on the east cost of Scotland, don't think the air temperature has been double figures for months, would this be a factor in it running hotter?

[Jim the Box]

Intend looking at the bongo over the weekend, I will take it for a run first, I have checked and the water level is fine, no apparent leaks, so if I do a 20 mile round trip with no excessive rise in temperature would that be considered a fair test to prove it's running ok?

[haydn callow]

Sounds o.k. But 50 miles would be better

[rita]

Hi,an efficient engine should run at its best about 85~90.It seems like you are not getting a true Coolant temperature reading.

[Driver+Passengers]

Whatever/wherever you're measuring, a step change in 'normal' temperature reading is a bit odd so you're probably right to query it. I wouldn't have thought a change in ambient would make "all that much difference" as it's a dynamic system with 'stat putting rad more or less in the system to maintain equilibrium. I'm only used to the diesels, though, and I could be wrong.

In my case (certainly not saying it's the same with yours!!) I was seeminly driving ok but it was 8-10 degrees hotter than usual. As it turned out, it was exhaust gas coming through the head gasket that was raising the temperature. Eventually, that developed into two or three big boil overs. I didn't pay enough early attention to the fact I was running so much hotter than usual, and instead started recording coolant pressure vs TPS as an indicator that the exhaust gas was getting in there. Anyway, I digress...

Keep watching it. Take notes.

[Simon Jones]

I'd have to double check my readings, but from memory I get around 80 on the rocker cover and 65 on the large hose exiting the o/s front of the engine. Also got a sensor on the hose from thermostat to the bottom of the rad. In current weather it ranges from about 10 - 15 degrees indicating that the thermostat is rarely operating in normal use.

[Jim the Box]

My bottom hose is only slightly warm at the moment, so was hoping the warmer weather was a factor with the engine temp.
Hoping to test tomorrow.

[rita]

You would probably be better with one of these rather than the original gauge.

http://www.ebay.co.uk/itm/NEW-2-52mm-BL ... 564be5d66d

[Jim the Box]

Think my sensor is doing it's job Rita, however that looks a pretty cool gauge you have sourced.
I took the bongo for a test run today the conditions were similar to last week, (13'c and a very, very strong westerly wind). I found that down wind for 20 miles, the temperature fluctuated between 80'c on the flat to 85'c on hills, however once I turned into the wind the bongo ran 76'c on the flat to 79'c on hills, I can only assume the increased airflow around the engine was a factor. I expected the engine temperature to increase when I turned into what was a very strong wind, but the opposite happened and the van ran at a temperature I'm accustomed to. Total journey distance was about 42 miles . My next trip is the Gairloch, I'm feeling a bit more confident I'll make it.

[rita]

Think my sensor is doing it's job Rita, however that looks a pretty cool gauge you have sourced.
I took the bongo for a test run today the conditions were similar to last week, (13'c and a very, very strong westerly wind). I found that down wind for 20 miles, the temperature fluctuated between 80'c on the flat to 85'c on hills, however once I turned into the wind the bongo ran 76'c on the flat to 79'c on hills, I can only assume the increased airflow around the engine was a factor. I expected the engine temperature to increase when I turned into what was a very strong wind, but the opposite happened and the van ran at a temperature I'm accustomed to. Total journey distance was about 42 miles . My next trip is the Gairloch, I'm feeling a bit more confident I'll make it.

Yes basically you are only measuring the temperature at the out side of the engine where the sensor is attached.There are so many factors that can effect this type of monitoring as you have mentioned, plus the internal state of the engine casing.I would think it might benefit with a shroud/shield over the probe.
I would imagine that if you wanted a more realist result it would be to fit a proper Coolant Temp gauge using the manufacturers sensor position and ignore the original gauge.

[Jim the Box]

Spot on Rita I was thinking the very same myself, will try some sort of shroud/heatshield, failing that will look at the fitted temperature sensor location to see what options I have. However, I think the TM2 would alarm out if I was having a boil up for real. I'm just so relieved that everything seems fine. If I do replace with the new gauge (shown in the thread above) I assume that the 1/8 sender they supply would fit directly into the existing temp sensor location or would I need an adaptor?

[rita]

Spot on Rita I was thinking the very same myself, will try some sort of shroud/heatshield, failing that will look at the fitted temperature sensor location to see what options I have. However, I think the TM2 would alarm out if I was having a boil up for real. I'm just so relieved that everything seems fine. If I do replace with the new gauge (shown in the thread above) I assume that the 1/8 sender they supply would fit directly into the existing temp sensor location or would I need an adaptor?

This is the one that should be fitted presently to your vehicle,the physical sizes are on the RHS of the page.

http://cn.oemol.com/oem/en_oem_detail/4 ... ensor.html

[mikeonb4c]

Spot on Rita I was thinking the very same myself, will try some sort of shroud/heatshield, failing that will look at the fitted temperature sensor location to see what options I have. However, I think the TM2 would alarm out if I was having a boil up for real. I'm just so relieved that everything seems fine. If I do replace with the new gauge (shown in the thread above) I assume that the 1/8 sender they supply would fit directly into the existing temp sensor location or would I need an adaptor?

I wouldn't do that. My concern with cheap goods on ebay would be reliability. Will their sender give the reliable operation over many years as the Mazda item. In reality, a mason modified temp gauge is doing the same job only without the numbers. Not as attractive a piece of eye candy as the ebay item I agree but...

And surely a tm2 does at least attempt to measure a local (head) temp, whereas the coolant system actively tries to keep temps within a working band and so arguably extra effort by cooling fans could mask a developing problem? The problem for the tm2 is to achieve standard fitting position on lots of Bongos so data on what is normal can be gathered.