Temp/fans issue?

[Critical_Mass 10]

Hi all,

 

Sorry to post yet another problem, especially when its a temp related issue.

 

Basically since my top rad hose sprunk a leak and i had to drain most of the system refill then get all the air out of it. The temp gauge sit at 90 as it should - it did before. Now it sits at 85 and can even drop to 70 when driving. I thought maybe the thermostat. But was told if its the thermostat the temp would continue to drop to zero.

 

If im in traffic, so stood still, it can go to 90 but when i get going again it will drop. Now, ive noticed that when sat in traffic the temp will creep up to 90, but then the fans kick in and the temp starts to drop again, then after about 30 seconds the fans go off and again, still in traffic, it'll creep up to 90 again.... it seems to loop like this. Today i noticed that if i had the heated rear window on it will do this loop, but the fan then kicks in at 85 - again fans on for about 30seconds temp dropped to 70 ish and then fans go off and temp creeps back up (still with heated switch on). I tried again with heated switch off and it did the 90 loop again.

 

Now i cant see how the heated window would be related and im thinking, the fan rad switch is faulty. But does this explain the low temps whilst driving. Could the fan be coming on whilst driving which is cooling the engine further whilst the air from driving passes over it also??

 

Oil temps are normal btw, even when water is 70.

 

Before all this months if not a year or so before, when i had driven the car and switch the engine off the fans would kick in not long after - this is normal. But the fan was irratic and would switch on for a second then off then back off, then may come on as normal, sometimes not. But the problem seemed to go away, but now the fans are acting up when driving.

 

Im thinking the fan switch as i said, but im not sure if there's more of an issue there??

 

Cheers

Gaz

[guildmage 11]

If im in traffic, so stood still, it can go to 90 but when i get going again it will drop.

 

Amazingly mine does exactly the same, thought it's not VR6 - must be the "Leeds issue" :) Will keep an eye on this thread.

[Critical_Mass 10]

Your issue could well be the thermostat. If there was an apparent fan issue id have said thermostat for mine too. Unless its both the thermostat and fan switch thats happened to go wrong at the same time.

[RW1 0]

All those symptoms you describe are exactly what I had in August. It was the 15 year old coolant thermostat being lazy. But also opening late slightly, ie. gap for temperaure was narrower in the thermostat, so forcing up the engine block coolant and oil temps a little.

 

Changed the thermostat and everything went back to normal with the rad fans on at a consistant setting. Running temps consistant and correct rather than slightly raised.

 

C.

[Critical_Mass 10]

Ok, so the thermostat could still be the answer. Though my thermostat was changed a couple of years ago - hasnt lastest long if it is foobar'd.

 

Infact it was changed in 2008 when new engine went in - is it normal for them to only last 4 years, or is that usual time period?

 

RW1- just another maybe unrelated Q. When i put the heated rear window on the green digital display lights dim a tad - not much, but it is noticable. Also when the indicator flashes they go dim intermitently. Is this a possible sign of the, probably original alternator on its way out?

[RW1 0]

Thermostats, known them to last only a few months.

 

Alternator, more check out the battery first.

 

.

[Critical_Mass 10]

Ok cool. I'll check the voltage across the battery tomorrow. Is this done with no engine running?

[nrc 0]

Check it with the engine off and on so you can get an idea of how well the alternator's doing. 12.5V or more when off and 13.5-14.5V running is decent.

[Macdaddy 10]

Am I missing something? This sounds normal to me, my VR will sit at 70 when moving but when stood still naturally the temp rises and the fans kick in.

 

Your electrical issues does sound like the alternators not doing its job. As suggested get it tested before it kills the battery too. Check the belts tight too.

Edited December 17, 2011 by Macdaddy

[RW1 0]

Am I missing something? This sounds normal to me, my VR will sit at 70 when moving but when stood still naturally the temp rises and the fans kick in.

In a way yes......

 

Its the inconsistant temp switching of the rad fans. As the thermostat gets tired, its not moving consistantly. This leads to different quanities of hot coolant getting into the radiator. The rad fan thermoswitch reacts to what it senses. The temperature switching of the rad fan switch went rapidly downhill over about 10 drives until it would switch on between 97'C & 112'C.

 

At running speeds, the oil and coolant temps would be almost the usual levels. But when you stopped in traffic, the temp rise would be as usual. But the fans kicked in on their first switch at a random temp in the above range. And only for say 30 seconds. The dash temp would budge downwards.

 

Put the thermostat in a pan of boiling hot water and you could see its slowness to react plus the opened area compared to the replacement was markedly reduced for a given pan water temperature.

 

New thermostat in and the coolant temps is the usual but the oil is running 6'C cooler now. Plus when the coolant heats up in traffic, it rises, the rad fans come on at a consistant temperature every time as per the rad fan stage 1 fan temp setting range (in my case 107'C indicated), the coolant then drops in temp with fans going off. Oil stays cooler as well with it remaing at a lower temperature despite the coolant rising.

 

-------------------------

 

Battery: As above, check the charge (still connected) with engine not running (after a descent run of 1 hour). After 6 hours, use this table

 

100% charged - 12.75 volts

75% charged - 12.50 volts

50% charged - 12.20 volts

25% charged - 12.00 volts

0% charged - 11.70 volts or less

 

If about 12.20 volts or less, then charge the battery up on an independant source (charger) and then leave again. If it settles after 10 hours to 12.20 volts or lower, then battery is definite past its best by far. Charging should leave it off charge settled at 12.4 - 12.50 volts usually. You will never get 100% with an older battery.

 

The final is a battery tester test at a garage to confirm.

 

When running, alternator should go to nominally 13.8 -14.0 volts. Anything less, check connection ALL joints of both 12 volts feed & earth return via the engine/gearbox for corrosion/high resistance.

 

.

Edited December 17, 2011 by RW1

[Critical_Mass 10]

It sounds normal??? im confused by that... ive never known it to be normal for the temp to drop to 70 even when driving. before this issue, certainly when the new stat was fitted it used to sit at 90 on the dot and there was little movement.

 

From what it was like before and what ive been told the temp should be around 90. Its never dropped to 70 before and has always been at 90 - which i believe is normal operating temp. In traffic id expect it to rise to 100 then the fans kick in until the temp drops to 90 again - which it used to do.

 

---------- Post added at 10:57 AM ---------- Previous post was at 10:54 AM ----------

 

Cheers for the battery check guys! :)