TDI300 overheating and air lock woes - any advice?

**stumps** · 13th October 2012, 05:27 PM

Hi all, Well it seems the dreaded overheating issue has come my way. I don't wish to bore everyone with details, but keen for any advice/tips. Here is background/what I have done so far:

* Had '97 disco for 3 mths. did 2000 kms all fine, no coolant leaks or top up required, till suddenly had an overheating event for no reason (doing 80 kph) and splurged coolant out the cap etc. I caught it with the temp gauge on the rise and shutdown quick. Have read of the gauge quality so reckoned I had certainly done the head gasket or worse...got it towed to mechanic. He conducted jacket water pressure test overnight. Could not fault. Road test no problem no overheat etc. Drove home bewildered, but then next day another half hour into a drive and it did it again.

So after all this, replaced radiator core (was filthy/majority blocked), replaced thermostat (found incorrect thermo inplace..not of correct diameter on recycle valve, etc as identified by others on here)..Genuine TDI type now in, replaced expansion bottle cap, replaced venturi vent hose assembly (old one partially blocked). ..theres not much left is there?

Checked each and every hose for state/kinked..all look relatively new.
Checked inlet to water pump with mirror...looked good without removing
Flushed entire system before removing radiator.
Once all back together bled system all sweet you'd think...but lasted 1/2 hour and did it again! WTF!

Have done some testing and can now get consistent results, pressurised or with vent cap off.
Once starting cold, vent line off top of thermostat flows well...but once warm/stat open and say about 20 mins, it all of a sudden just air locks up! (as deduced by heater air going cold and vent line flow stopping)...then a few minutes and splurges and out the cap. Head gasket? but when cold or in testing cannot see any bubbles or contamination of coolant at all?
I reckon I am purging air well, and in the static cap off test I have the expansion tank coolant level raised well above engine...same thing.
Checked hoses and they dont appear to be collapsing on inlet side.

Then only other odd bit off info is that the previous owner replaced the head about 1 month before he sold it...(now I know why!

).

Any tips before I get the head off...my concern is that a new HG or head may not be the answer here. I don't know the type of head that is on it , but is there any potential mismatching of head to gasket to block that is causing problems. (Had new motor about 30000 km ago). As always appreciate any comments, hope I have explained sufficiently.

**justinc** · 14th October 2012, 07:55 AM

sounds head gasket related to me, unfortunately

pressure like that has to come from somewhere, diesel engines require a very small leak to cause big issues as they have huge compression/ cylinder pressures. Usually a die test on a Tdi or Td5 won't show much unless the gasket is well and truly blown, usually you have to drive it up a hill to get the pressure up, if there is excessive pressure there on a relatively cool/ warm engine after a quick load up a hill then it is most likely a gasket issue.

jc

**slug_burner** · 14th October 2012, 12:35 PM

Stumps

If you say head gasket change before sale, then the job may not have been done properly to keep costs down. Did they resurface the head? Did they use the correct head gasket, I think there are three thicknesses.

Justin is a diagnosis king so you probably have your answer. If you don't want to do the work yourself make sure you get onto someone who knows LRs.

**justinc** · 14th October 2012, 03:03 PM

Originally Posted by slug_burner

Stumps

If you say head gasket change before sale, then the job may not have been done properly to keep costs down. Did they resurface the head? Did they use the correct head gasket, I think there are three thicknesses.

Justin is a diagnosis king so you probably have your answer. If you don't want to do the work yourself make sure you get onto someone who knows LRs.

steady on slug, i'm only human

jc

slippery · 14th October 2012, 03:17 PM

Or it was sold because it has a cooked head and they could afford some $1,300 odd for a replacement.

**slug_burner** · 14th October 2012, 04:54 PM

Originally Posted by justinc

steady on slug, i'm only human

jc

I said king, not god or guru. You appear to be pretty good at it with the experience to back it. And yes very human we are glad to say, otherwise you would not go the 4bdt1 shaker.

**justinc** · 14th October 2012, 05:02 PM

Originally Posted by slug_burner

I said king, not god or guru. You appear to be pretty good at it with the experience to back it. And yes very human we are glad to say, otherwise you would not go the 4bdt1 shaker.

Ahh, well I am not too comfortable with any of those descriptions, hence the previous post, but I appreciate the sentiment all the same

JC

**stumps** · 15th October 2012, 10:46 AM

Thanks for comments and opinions guys.
Yep I reckon I am in HG denial. I have it booked in this week to a Landy guru to get it off and fully check head, block face etc and go from there.
The tragedy out of all this is the head is only 3000 km old...the block less than 30000 (both from overheating events). Previous owner had spent a bundle on it and gave me all receipts, yet with all this work there is no history of radiator check/overhaul. When I pulled it out the radiator and had the tanks removed, it was absolutely putrid in the inlet core side...blocked like I have never seen before...explains why everything has broken I guess. And as for that thermostat mismatch..uggh!

I will hang in there and get it right, the rest of the car is in great condition and has only 172000 on the odometer.

**bigcarle** · 15th October 2012, 03:02 PM

and also get a engine monitor of ebay from Salisbury in Brisbane to stop any future events

**Blknight.aus** · 15th October 2012, 08:04 PM

I dont think this will work (Im backing JC's theory) as the symptoms dont match a thermo failure but

remove the purge line valve (Part #9) and the thermostat. replace the purge valve with a simple T piece

If that works your thermostat isnt opening enough and you're just boiling it out.

IF you're lucky its just shoddy workmanship on putting the headgasket in and all you'll need is a new gasket and bolts. A blind freddy clue to this will be having a go at torquing up the head bolts to about 120nm, if you can tighten a bolt at that low a setting then it wasnt done properly the first time and somethings let go.

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