Temperature Gauge - Funny readings

Pizzer11 · Post by **Pizzer11** » Sun Jan 20, 2008 8:21 pm

Hi All,

Summary - can someone please tell me what a temperature gauge should read when driving on the motorway at about 2500rpm and 65-70mph?

Background - I have just had an API Engine (Refurbished Unit) installed by MD Motors. I drove it down and back to Exeter from London over the weekend. Took it easy down and pushed it a bit more on the way back. Engine ran and sounds fine; however, when cruising on the motorway the temperature gauge does not register anything, sitting at it's absolute min (about 9 O'Clock). On the return journey I pulled in to a Services and sat there for 5mins with the engine running and the temperature rose to about 11 O'Clock or just below halfway. Once I was back on the M3 the temperature slowly dropped back to absolute minimum. Once in London and travelling amongst traffic, the temperature started to register between quarter and halfway.

Assuming this is not how it should be, can anyone tell me what the problem is? My assumption (as a complete newbie) is that the temperature gauge or thermostat needs to be calibrated or something. I'll more than likely take the van back to MD Motors to be fixed, but just wonder if anyone has experienced this before. Obviously after just replacing my engine, I'm keen to have the temperature gauge working properly. Also, on the way down the engine would (all of a sudden) idle quite high, sometimes at 1000rpm and as much as 1750rpm, for several minutes then drop back to normal idle revs as quickly as they had jumped up. Thought this might have something to do with the fuel pump or linked to the faulty temperature gauge, but it seems to be doing it less now that I've done about 400 miles.

francophile1947 · Post by **francophile1947** » Sun Jan 20, 2008 8:31 pm

It sounds like a faulty/missing thermostat - the gauge should normally sit at around 11 o'clock. Is the heater blowing hot when on the motorway?

Harry · Post by **Harry** » Sun Jan 20, 2008 9:12 pm

Once warmed up properly (takes about 10 minutes of normal running under load) the temp guage should read at about 11.00 - 11.30 and never moove again until the engine is shut down.

H

haydn callow · Post by **haydn callow** » Sun Jan 20, 2008 9:18 pm

Sounds a bit odd to me. As everyone says 11 o'clock is good. Sounds as though they forgot to put a thermostat in or it's jammed open.
Was all O.K. before the new engine??

mikeonb4c · Post by **mikeonb4c** » Sun Jan 20, 2008 9:40 pm

Any chance that electrical connections have not been well made during install of the new engine (poor earthing to chassis maybe?). You need a mechanic for this one but I've learned that sender units can misread (fuel for instance) due to poor electrical contact, and also that engine RPM can be varied by signals from sensors like the one for the aircon etc. Might be worth checking on this aspect. Are your heaters giving hot ari? Is the bottom rad hose warm etc. as that would suggest engine temp is fine and the gauge is misreading. This might a good opportunity to fit an engine block temp. sensor as others have done (clogger comes to mind, Missfixit too I think). If you put yours where theirs are (oooh matron) you'd be able to do comparative testing.

Good luck

Ralph · Post by **Ralph** » Sun Jan 20, 2008 10:05 pm

If the gauge is reading true then it's likely the thermostat
is stuck open or missing, the revs going up could be due
to the cold start system being fooled into thinking the
engine as just been started from cold and upping the
tick over.
Main thing is to make sure it's running cool and not got
a air lock check the water level see if you can feel any
warmth at all from the heaters, the temp gauge sits
at about 11 o'clock after about 2 miles normally if all's well.
If the heaters are working well it's likely to be a loose
wire on the temp sensor or bad earth.
What ever you do don't drive it if it's over heating running
cold wont do any harm in the short term but needs fixing.
Running hot will kill the new engine.
Take it back get them to sort it.

Pizzer11 · Post by **Pizzer11** » Sun Jan 20, 2008 10:09 pm

Thanks all. I'm confident now that there is something wrong. I believe that before the engine was cooked the thermostat and temp. gauge worked fine and the heaters are blowing hot air. Prior to going for the full engine replacement, MD Motors thought it was a standard head gasket problem and in treating it as such we replaced the thermostat. I assume the "new" thermostat is still fine and it must be some sort of connection issue. If there was no connection or no thermostat I would've thought that the gauge wouldn't register anything at all, but it is confusing that it seems to register temps whilst travelling in the city but no temp when cruising.

I will look at the engine block temp. sensor things but as I'm 2-weeks from leaving for France and the Alps for 7-weeks, an operating temp. gauge may have to suffice!

missfixit70 · Post by **missfixit70** » Sun Jan 20, 2008 10:37 pm

Do you know for sure what caused the "head gasket problem"? Was the radiator checked for flow?
As Mike said, I've got a cheap little temp sensor that I got from ebay, took 2 minutes to silicon the probe in a spare threaded hole in the top of the block. unfortunately it isn't backlit, but it's better than nothing if you want an actual temp readout. Cost about £7 I think.

mikeonb4c · Post by **mikeonb4c** » Sun Jan 20, 2008 11:35 pm

Given that the temp gauge is electrically damped anyway (the Mason Alarm works by 'undamping' the gauge) the poor connection could make senset, as if voltage reading is low the best it will manage is to go from low reading to something like normal. Its easy to imagine connections being disturbed and not remade firmly if chargeable labour is trying to get a big job like that done quickly. At the end of the day you'd think if heater feels right, bottom hose feels right, its not boiling or losing coolant then a tragedy would be unlikely.

But getting back to reality, the suppliers should be faced with this problem and asked to look into it. The racing engine is not something you want to live with either.

Good luck - keep us posted.

patmckenna · Post by **patmckenna** » Sun Jan 20, 2008 11:47 pm

Hi Pizzer,
Have sent you a pm. Pat

Pizzer11 · Post by **Pizzer11** » Mon Jan 21, 2008 1:34 pm

Thanks for all the advice. I've been advised to consider my warranty terms with API Engines before I get my mechanic to change/replace anything on the engine. As such, can anyone point me in the direction of a webpage/weblink that provides more information on these engine block temp. sensors things?

More Background - The engine overheated in France whilst in the care of my parents who were over from NZ. The water hose under the driver's seat burst. MD Motors did all they could but in the end we decided to replace the engine, radiator and the existing coolant hoses for a set of the silicone hoses Flippa stocks.

missfixit70 · Post by **missfixit70** » Mon Jan 21, 2008 9:30 pm

This is the digital temp probe & display fitted. I used high temp silicon sealant to fix the probe in one of the threaded holes on the passenger side of the engine & ran the cable up through into the cab & used double sided sticky things to mount it on the dash below the stereo.
Got mine up to 108 degrees today towing a folding caravan up a fairly steep hill & still accelerating, stopped in a layby halfway up to make sure the caravan was still in one piece ( only slightly falling apart

) & when I turned on the ignition my mason alarm was binging away

, so I've turned it up a smidge to between 4.5 & 5. Glad to know it works when it's supposed to

missfixit70 · Post by **missfixit70** » Mon Jan 21, 2008 9:37 pm

You may well find that even within normal bongo operating temperatures, the wax seal things that these guys rely on to check whether you've cooked the engine will probably have melted. There has been discussion about this in relation to warranties not so long ago if you have search.
I know I had mine up to 114 degrees not long after I fitted the gauge & others including Brorabongo have had similar readings, all perfectly normal it seems, if slightly disconcerting watching the temp go up

brorabongo · Post by **brorabongo** » Mon Jan 21, 2008 9:45 pm

I too have the same display, and regularly get temperatures around 110 deg. I've had it off the scale one day recently, that means over 119 deg's.

After S**ting myself that something nasty was happening, I found that the probe had fallen out of place and landed on the exhaust manifold cover.

So if you go down this route missfixit's idea of using the high temp silicon is the way to go.

petebee · Post by **petebee** » Mon Jan 21, 2008 10:17 pm

Hi pizzer11 mine behaved exactly as you described new thermostat fixed it

good luck