300tdi overheating and not de-pressurising.

**redneck.woman91** · 2nd July 2011, 04:24 PM

Hey everyone,
does anybody have a suggestion as to what could be causing my 300tdi defender to majorly overheat? And also why sometimes it doesnt actually overheat but it just wont release the pressure from the radiator and tubes, even hours after the utes been turned off?

We had to replace the head gasket because it blew around 6 weeks ago (not causing any other issues except for a funny noise and crappy fuel economy), and up until the last week everything has been fine. Then Dad noticed it wasnt de-pressurising after i turned the ute off, but there was no sign of overheating or sluggishness.

On Wednesday she overheated BIG TIME. I noticed a burning smell for a minute, and while I was trying to figure out where that was coming from, the temperature gauge shot off to the end of the red.
After pulling it up, opening the bonnet and waiting 15 minutes for the grumbling, gurgling and steam to stop, I undid the top coolant reservoir and noticed it was now bone dry when it had been full when I left home, and the head and my radiator tubes were all boiling hot.

When Dad came to rescue me off the side of the highway 4 hours later we filled it up with water, and managed to get it another 10km before it started to overheat, so we pulled up again. Dad checked everything, my coolant was barely lukewarm but my head and tubes were boiling. We figured we would disconnect the thermostat (a trick we learnt with another overheating 300tdi) and limp it home. What do you know, the thermostat wasnt opening. Once we pulled it out, we got it home and the head, tubes, and coolant were lukewarm/almost cold. We figured that the thermostat therefore must have been the problem, so we got a new thermostat and after putting it in Dad drove it everywhere today. It was running a bit hotter than usual (at normal operating temperature it was on halfway on the temp. gauge where before it would have been at a quarter.) and 3 times jumped up to the end of the white line, but then very quickly went back to halfway. We thought that was a bit odd, but other than that everything was working fine, and coolant was luke warm at all times.

The bloody thing overheated big time again this afternoon, dumping coolant on the road and hitting the edge of the red on the temp. gauge. We disconnected the thermostat and got about 1km down the road before it overheated again, then we had no issues to get it back home.
Can anybody please explain what the hell is going on? Because if this keeps going i will have to sell it

**GuyG** · 2nd July 2011, 05:11 PM

What sort of condition is the radiator in? Has it been rodded recently?

**roverrescue** · 2nd July 2011, 06:23 PM

Me be thinking your still getting combustion gasses and water jacket sharing the love. Your symptoms all sound very head gasketty!

-Was the head level / skimmed before replacing gasket?

-Was the deck level and clean before fitting?

-What gasket did you use in the replacement?

S

**redneck.woman91** · 3rd July 2011, 03:32 PM

Hi there

Radiator is around 18 months old if that, and pretty clean. Theres a few bugs and a bit of mud on it but nothing substantial. And yes its been rodded

Checking the radiator was actually the first thing we did when we pulled it off the road to do the new head gasket lol.

Yes the head and deck were both level and clean when Dad put the new gasket in, he was very careful about making sure there was no damage done to it as he thought maybe after 15 years and a stuffed head gasket, my head could have been wrecked.
We got 1 of these new German metal gaskets from a 4wd parts supplier in Newcastle, and we were both a little concerned about that lately as we have been told that could cause an issue?

**Blknight.aus** · 3rd July 2011, 03:40 PM

sounds like the head to me but it could also be the waterpump impeller failed or the VC not transmitting drive to the fan.

leave the filler plug off of the thermostat housing and start it up.

if theres no coolant flow its the pump

if the fan spins on for more than a second after shut down its the VC

if as soon as you start it up its blows coolant out the filler its the head.

Thats not exhaustive but a very quick indication for worst case scenario for all 3 items.

**justinc** · 3rd July 2011, 04:38 PM

Regarding those metal shim gaskets, i never use them unless on a newly machined block surface, I have had 2 leak in the past and after switching BACK to composite gaskets (Elring genuine type) I have never had another issue. I won't use them now.

I think that your symptoms best describe another head gasket leak. At least they are easy to remove/ refit.

JC

**redneck.woman91** · 4th July 2011, 11:05 AM

So it could be that gasket??
We have used one of them at least once on our old Discovery, and we believe they were used another 2 times on the same vehicle with different mechanics, becasue they are cheaper and easier supposedly..... the whole time the Disco had the same issues as my ute and in the end Dad gave up and sld it for scrap after the gasket blew again after 3 months.
I dont want to lose my little ute, so I hope the head isnt damaged

**Blknight.aus** · 4th July 2011, 12:20 PM

for the metal shim gasket to work properly you need the deck and the head face to be perfect AND to have the correct surface finish, the elring gasket kits are a lot more forgiving.

IF it was me, my next step would be to pull the pump pressure flush the radiator replace the P gaskets and have the head crack and pressure tested. IF the deck and the head are ok Id then be putting it all back together. At this stage if its a gasket mating problem its likely you can save the head if you get on it promptly.

**redneck.woman91** · 4th July 2011, 03:09 PM

The P gaskets were replaced 1500km or so ago when Dad remembered to haha. Will do with the radiator, I think its OK but Id rather be sure.
Around here we have nowhere to send the head to

**Blknight.aus** · 4th July 2011, 05:27 PM

given that....

how goods your workshop gear, I can probably talk you through how to build a pressure test jig for doing a cooling system pressure check while the heads off.

your going to need some 3-5mm flat plate
something to weld some angle iron onto the back of it
some decent angle iron
something to drill some holes in it with
some 5-10mm rubber sheeting
fittings to seal up the head and apply pressure to it
something to heat the head up to 80 degrees with (the kitchen oven or a bbq oven works well)

if you dont have a decent engineering straight edge (and no, I dont mean a steel rule) you can improvise it withe a lot of patients, some feeler gauges and a laser pointer.

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