3/4 temperature and no fan...

[aidan]

The temperature on my GTD goes to 3/4 very quickly. It never goes above or come back down, and it doesn't change regardless of my speed, i.e I can be sat in traffic at that temperature, I can be on the motorway at 60 at that temperature, and I can be thrashing it around 30-50 up hills etc at that temperature.

I got it to that temperature and let it idle, the fan wasn't coming on.

I previously had a problem where the car wouldn't warm up at all past the lowest stop on the gauge, I would have no heat in the car. Then it suddenly went to half way and stayed there, I would have plenty of heat in the car.

There is now no heat through the heater in the car.

There is pressure in the header tank, presumably from this overheating.

Does this all point to faulty thermostat?

[jtanguay]

it could actually be a faulty expansion tank cap.  your best bet would be to try and bleed the system by running it without the expansion tank cap on.  use a thermometer to see what the temp is.  it should drop around 86.5C or so.

[Vincent Waldon]

Nine times out of ten funny temperature behaviour starts at the thermostat.. the Bentley has the proceedure for testing... if you replace it be sure to test the new one... they have a long and honoured history of being bad from the factory... doesn't seem to matter which brand.

Second guess is the impeller spinning on the water pump shaft... I'm guessing your's is a mid-80s TD so at least you don't have the plastic impeller of the early TDIs, but spinning is not uncommon.

Third guess is some kind of blockage, collapsed hose, nasty air bubble, etc.  When you check/change the thermostat or look at the pump you'll have the opportunity to drain the coolant and give the system a good flush... any funny sludge in the old coolant ?

Fourth guess is the expansion tank cap as previously mentioned... I've read about a recall on the black ones and blue replacements... mine is black and I've never had a problem but if they malfunction weird pressure things can happen which turn into weird temperature things.

Good luck.. tell us what you find out !!!


Vince

[aidan]

It had a new blue cap last week.

Its a 1991 SB GTD. I bought it around 3500 miles ago with a bust front engine/gearbox mount, the whole thing tilted forward and the alternator cut the lower radiator hose.
I refilled it then, purely through the expansion tank.
The lower hose came off again unfortunately a few weeks ago, emptying all the coolant again.

It overheated a little last week, when opening the cap at least 2 litres of coolant came out. Running the cap a little loose so the pressure doesn't get high has probably lost a couple more litres.
Basically its had about 3 cycles of coolant in 3500 miles if you know what I mean.

The coolant is fine, no sludge. There is no coolant in the oil. The oil level has not dropped in the slightest since I had it (did oil change when I got it)

[Vincent Waldon]

Fifth guess (we're really in the weeds now!)... head gasket leak, causing compression to pressurize your cooling system.  Did the lower rad hose fall off or explode off ??

Classically the test for this is to start the engine from dead cold... let it run for a minute or so, stop the engine, and then unscrew the expansion tank cap.  If it hisses it's probably being pressurized from a leaky head gasket (too soon for heat to have caused pressurization).   A proper compression leakdown test can done to confirm.

Any idea how many miles on the head and gasket ??  Did it overheat the first time enough to warp the head?


Vince

[aidan]

The hose fell off, it seems the lower outlet of the rad was slightly damaged when the alternator dropped.

I started it earlier and held my hand over the top of the tank, couldn't really feel any pressure building up. Took the cap off shortly after starting it the other day and no hissing.
I will go and try it again now.
When it was running cold though, I could take the cap off in the morning and it would hiss and spit out a bit of coolant.

I believe the head and gasket are original, so around 146,000 miles and 16 years.
When it overheated the first time I would say it could have warped the head, as it was steaming from the engine bay, and there was constant faint white smoke from the exhaust.

[aidan]

Ok, just started it for a minute or so,
There is pressure build up - when the cap is released its kind of a burp, definitely not a hiss? Probably the same thing I guess

[Vincent Waldon]

White smoke in the exhaust, hissing/burping from the coolant tank when cold... doesn't sound good for the head gasket.  

Quickest thing now would probably be to check compression... or ideally do a leak-down test so that if there really is a leak you'll pinpoint it exactly.

[jtanguay]

hmm yea those problems suck.  at idle my temp is perfect.   the fan even comes on!  but when i'm driving down the highway the temp gauge will creep right up and fan does not kick in (so the hot coolant is not getting to the rad...)

[aidan]

Sorry the white smoke was only that at that first overheat, doesn't do it now.
I think the head gasket is the likely culprit, oh well its only a work beater i'll see how it goes.

More worryingly I noticed the clutch release bearing rattling last night, very loud, and today when coasting along around 1000rpm in 4th a very strange rumbling sound from the gearbox, went when the clutch was depressed. I'm more worried about the gearbox letting go first to be honest.

[jtanguay]

hmmm its not a good idea to be driving 1000 rpm in such a high gear... think of all the stress the crank is under!  I find that if i am going downhill, or on a level ground, 1000 rpm is fine.  it's whenever i'm going up an incline that the engine starts to vibrate because it doesn't like it.  saves fuel yes, but remember to downshift when the engine is getting stressed.

gotta love diesels though! gasser's get fouled injectors if ran at low rpm's... we can run low rpm's all day long 365

[aidan]

It was just slowing down, and basically pulling itself along then, I wasn't touching the accelerator.

PS Jtanguay see if this seller has anything that interests you http://search.ebay.co.uk/search/search.dll?sofocus=bs&sbrftog=1&catref=C6&from=R10&satitle=iveco+diesel+pump&sacat=-1%26catref%3DC6&sargn=-1%26saslc%3D3&sadis=200&fpos=B987XT&ga10244=10425&ftrt=1&ftrv=1&saprclo=&saprchi=&fsop=1%26fsoo%3D1&coaction=compare&copagenum=1&coentrypage=search

[jtanguay]

hmmm those iveco pumps are IDI right? still not too bad of a price :wink:

[addautomotive]

it could actually be a faulty expansion tank cap.  your best bet would be to try and bleed the system by running it without the expansion tank cap on.  

I think this is great advice...

The fact that you have NO HEAT points to an air lock somewhere in the system. I find this sonetimes happens when you change the main hoses, or splice into the system.

In fact, I just battled the exact same symptoms in my Samurai last week. I had spliced in long coolant lines for my SVO tank, and didn't bother to prime them with coolant. Lo and behold, I ended up with an air lock. Friggin thing would overheat without even having the thermostat open, and no heat to the cabin. There wasn't proper circulation.

Running with teh expanion tank resevoir opened was sufficient to "burp" the system, but sometimes I find I have to undo the upper rad hose from the rad, and fill the block from it.

[clbanman]

hmm yea those problems suck.  at idle my temp is perfect.   the fan even comes on!  but when i'm driving down the highway the temp gauge will creep right up and fan does not kick in (so the hot coolant is not getting to the rad...)

That's a classic symptom of a slipping impeller.  At lower rpms it's likely moving enough coolant that your fan comes on.  At higher rpms it slips enough that it stops moving coolant, the fan doesn't come on because the coolant in the rad is below your sensor temperature.  We had a few Cummins engines at work with this problem right from the factory.