Temp gauge all over the place after new head

[jaydee]

Hi guys, I havent posted much since I joined because my 3.0 Surf lasted one day before I realised the head was knackered and it then took 6 months to get it back on the road again (a long story I won't go into)

Anyways I've had her running with the new head now for about a month, and until a few days ago all was tickedy boo.

But the other day I noticed the check engine light come on for a few seconds, at almost the same time the temp gauge dropped from the middle to the cold position, where it stayed for a little while before jumping back up to the middle.

I was on the A14 at the time so I had to wait for a Layby to pull over and check everything was ok with the coolant system. So I wacked both the heaters up to hot (which they both did fine) and then pulled over.

I couldn't see anything wrong and by now the temp gauge was back in the middle again so I continued, with the heaters on full hot just in case.

The gauge dropped to cold a few times and the check engine light flashed on a few times but I made it to my destination no problems. When it had cooled down I took another look under the bonnet, the coolant was to the top of the rad and the header tank was full so to be honest I started suspecting a fault with the gauge or the temp sender.

On the way back the gauge didn't move at all from the middle and the check engine light stayed off for the whole trip back (about 60 miles). Anyways this morning the gauge dropped to 'cold' and has stayed there throughout the whole day.

Does this sound like a faulty or loose temp sender? Or a faulty gauge? Both heaters are still blowing hot and as far as i can tell there's no sign of overheating.

I'm just paranoid because the last time I saw that check engine light it cost £1500 and she was off the road for 6 months

[nero279]

Does this sound like a faulty or loose temp sender? Or a faulty gauge? Both heaters are still blowing hot and as far as i can tell there's no sign of overheating.

Sounds like a dodgy sender or loose connection to me, but i'm no mechanic.

[jaydee]

I'll take a look at the connection when it stops raining, the gauge is in the 'cold' position nearly all the time now. Am I right in thinking that if both heaters are blowing hot then this could not be an airlock causing it?

[Tallyman]

You are right about the heaters being hot not being airlocked. One earlier comment you made suggested both the rad header and the expansion bottle were full. That is wrong, as the expansion bottle should only be filled to the MAX mark on the bottle with the engine cold, otherwise you will lose coolant.

Check the engine after a run with it still ticking over. If your guage is showing cool but the top hose is hot then it's probably the sender either knackered or a lose or broken wire. The standard guage is never that accurate anyway as it usually stays smack in the middle over about a 50C temp range according to my additional temp guage.

[Holley-A]

Sorry to hijack this thread but is it worth adding an extra temp gauge for a more accurate indication of the engine temp, are these 3.0l surfs that prone to blowing heads i thought it was mostly the 2.4 hence thats why i got a 3.0
My gauge stays constant sofar the engine warms up and the gauge stays bang in the middle, regaurdless of traffic or weather conditions, as i am always watching oil pressure and temp when im driving

[TonyN]

Sorry to hijack this thread but is it worth adding an extra temp gauge for a more accurate indication of the engine temp, are these 3.0l surfs that prone to blowing heads i thought it was mostly the 2.4 hence thats why i got a 3.0
My gauge stays constant sofar the engine warms up and the gauge stays bang in the middle, regaurdless of traffic or weather conditions, as i am always watching oil pressure and temp when im driving

The 3.0's don't blow heads like 2.4's, I don't think is an issue, you're just seeing an average amount for any engine. The Toyota guage isn't the most accurate in spotting small differences in temp, and an after market gauge with temps on it as a good way of spotting when are warming up.

[jaydee]

yea it seems that I am the lucky one who had a head go on the 3.0ltr a few days after i got it

That'll teach me for getting a bargain eh.

I'm just hyper nervous about it overheating again though cos last time was so expensive and drawn out.

Might look into fitting an auxillery gauge anyway just for piece of mind.

[toyotav84x4]

The head on my 3.0 was cracked when I got it. Showed absolutely no symptoms till I blew the radweld out with redex and a heavy foot on day one.
Yes, a cheap second, third or whatever hand 3.0TD.

After I replaced the head myself with a new genuine one from Stevo I have had bang on temp just below the halfway and it doesn't move other than that.

As the other members have said a digital aftermarket gauge is a really good idea.

I was and still am hyper nervous about the cost to repair so upon rebuild and test I used a digital mulitmeter (gunsons pocket) with temp bulb sensor which I just pushed against the spanking new head and hoses to get readings. Amazing what you can disocver about the engine temp. Mine would not really warm up over 76deg unless driven then stays amazingly constant around the thermostat temp at 82 degrees.

You really should, as previous advice, check connections and add an aftermarket digital gauge. Otherwise park it. Let us know what it was though.
I will be adding a temp gauge as I want to see what happens while booting it and under towing conditions. There maybe cooling modifications required in the summer but I don't think the head will crack in my hands. "I'm alright it's everybody else", said the madman!

Now I am very pleased with the surfs comfortable ride, seats, smoothness and power. I guess I shouldn't complain all in all as I have bought and run a V8 hilux for 7 years and now the surf. Total cost equals that lost on a new car as it's driven off the forecourt!