300Tdi Cooling System Problem

**awabbit6** · 28th July 2008, 08:38 PM

I have a problem with my Disco’s cooling system that I think is a blown head gasket, but I’d like to hear the opinions of some forum members, before I go removing the head.

The symptoms go like this …
First noticed a pool of coolant under the car. On inspection, the header tank was full and under pressure. Coolant was blowing past the cap. Once cooled, I found that the engine was low on coolant, while the header tank was overflowing. I purged the air out of the engine and drove it to work the next day. On returning home, I found the same problem. Again, I bled the system and repeated the trip the next day. On the way to work, I noticed that the heater wasn’t working. I then looked at the temperature gauge as it began rising rapidly. As I was about to pull over, the temperature dropped back to normal and the heater began working as normal.

Over the weekend, I checked the system and again found the header full and the engine low. While running the engine I noticed bubbling in the thermostat housing. At this point, I drew my conclusion, but wanted to be sure, and used the car again that night. On this trip however, coolant was drawn back into the engine and the low coolant alarm gave a couple of ‘chirps’. On inspection, the header tank was low …

Drove to work this morning and it’s back to the original symptoms including the heater not working, then working again.

Thought I’d check the thermostat and bought one on the way home – aftermarket one and didn’t fit. The original thermostat functions perfectly though. It’s back together now for tomorrows trip to work.

Finally a bit of history. I’ve had the car for 2 years. The previous owner had a new head put on it (presumable due to overheating). Over Christmas while towing our camper, it was getting hot (but no-where near overheating) while pulling up hill, so I pulled the radiator out and had it cleaned out (30% blocked). It’s been good ever since … ‘til now …

I’d love for someone to tell me I’m wrong, but the symptoms are all pointing to one cause.

Paul

**Blknight.aus** · 28th July 2008, 09:13 PM

I have no good news for you...

unless youve got the mother of all bleed out problems (check your bleeder hoses arent blocked) and the pump is shifting the coolant then that sounds susly like the beginings of a head gasket on the way out...

First up run it without the thermostat in the housing and eyeball the coolant flow if your getting good flow from cold then its not a pump problem.

If your really really lucky you might get away with redoing the tension on the headbolts but thats not likely.

I strongly advise not driving it any further, IF its not giving trouble on starting and the coolants not pulsing then it might be salvageable.

**awabbit6** · 28th July 2008, 09:19 PM

Thanks Dave. The pump seems to be working fine and it starts prefectly. I'd considered re-tensioning the head, but I think if anything, I'll just be prolonging the inevitable.

Sometimes, I hate it when I'm right ...

Paul

**350RRC** · 28th July 2008, 09:21 PM

Hi Paul,

Had same symptoms with a RRC with 350 Chev.

Turned out to be a combination of dodgy hose clamp at the very top of the cooling system on gas convertor letting air in when cooling down, combined with dodgy rag cap on overflow tank.

Had the dreaded bubbles in the rad, etc and thought the worst. It was just air getting in the system while cooling.

Check all your hoses and clamps and make sure the rad cap is sealing properly and the little vacuum valve in it is not stuck.

Park on an angle when cold so that the opened plug in the rad is the highest point in the cooling system and run till the thermostat opens.

You'll see heaps of bubbles going past. Keep adding coolant, squeeze the hoses and see if the bubbles stop.

You might be lucky like me!

cheers, DL

**awabbit6** · 29th July 2008, 07:06 AM

Originally Posted by 350RRC

Had the dreaded bubbles in the rad, etc and thought the worst. It was just air getting in the system while cooling.

I suspected this as the cause initially, but have since eliminated it as it is pressurising while running rather than after running.

I got 10mins from home this morning when the temp rose and didn't drop - I turned around and came home.

If no-one else has any suggestions, the head is coming off as soon as it cools down.

Paul

**JohnE** · 29th July 2008, 10:38 AM

i know this is going to sound stupid and its 3 hrs after you put the post on, maybe you haven't done it yet.

But have you checked the water pump to see if the vanes are still there. I had a toyota years ago that was getting hot and hot changed the thermostat didn;t change the hot, then took the ater pump out and the vanes were almost corroded away, no water movement. And that was a 4 year old car! I had it since new and it was dealer serviced, before I woke up to their antics.

john

ps I'd give you a call but cant; find the no.

**awabbit6** · 29th July 2008, 11:52 AM

Originally Posted by JohnE

i know this is going to sound stupid and its 3 hrs after you put the post on, maybe you haven't done it yet.

But have you checked the water pump to see if the vanes are still there. I had a toyota years ago that was getting hot and hot changed the thermostat didn;t change the hot, then took the ater pump out and the vanes were almost corroded away, no water movement. And that was a 4 year old car! I had it since new and it was dealer serviced, before I woke up to their antics.

john

ps I'd give you a call but cant; find the no.

Hi John,
Just going to crack the head now. I'm pretty sure it isn't the water pump because once the themostat opens the water flows an the temperature is stable. It's a good thought though and I will double check it before taking the head off.

Paul

**JohnE** · 29th July 2008, 07:38 PM

oko doki it was just a thought, could just be something small( i hope)
btw the pump vanes on the toyota were a lot bigger than those on a disco and half corroded it made a difference, so i don't know what a disco would do.

john

**awabbit6** · 30th July 2008, 07:18 PM

Well the problem was obvious once the head came off. Both cyls 2 and 3 were blown into the water jacket. I haven't cleaned the surfaces up yet, but first checks with a straight edge indicates no damage to the head. Cause of the head gasket going isn't obvious, but I did notice that several of the head bolts were not as tight as I expected - infact they could have been loosened without the aid of a breaker bar. Perhaps the head wasn't tensioned properly when it was replaced by the previous owner.

I did find some other problems as I dismantled to remove the head too. One bent pushrod and the exhaust manifold was loose (one stud missing and only two nuts were tight).

If nothing else, this has been a good oppotunity to christen the new shed as this is the first big job I have done in it.

Thanks for all the input so far.

Paul

**Blknight.aus** · 30th July 2008, 07:35 PM

the most common cause of the center headbolts being loose (when its not a failure of the bolt/head) is not following the "magic number" correctly or doing the bolts up "in sequence in stages"

make sure your torque wrench is spot on as well...

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