simonb Posted June 9, 2007 Share Posted June 9, 2007 The 90 blew the head gasket last wknd between no 4 cyl and 8 push rod hole. I've done approx 100k miles since I got the 90, the vehicle was fitted with a service exchange engine when I got it (at 4 years old) - probably as the original suffered the a cambelt failure blow up - its a 94 300Tdi. Total vehicle mileage is 167K, so this engine may have done more like 130k miles. Question 1 - ive heard 300Tdis blow the head gasket, so is this failure common? Interestingly LR have superseeded the head gasket and its now a multi layer metal assembly not the composite type of the original. The head has been checked as not warped, but its got cracks between the valve seats on cyls 3 and 4. There are cracks round the injector holes on the same cylinders. Cylinders 2 and 3 have very minor cracks running in a straight line from the glow plug holes away towards non the "valve side" of the head. Now the cooling system remained full and pressurised when the gasket went. I have a Racetech temp gauge fitted as the original one is cr*p. It always sits at just about 90 degress. I don't loose coolant and all 4 pistons had carbon on their crowns - there was no evidence of the crowns being steam cleaned by leaking coolant. I have an EGT fitted which never goes beyond 620 degrees flat out on a motorway hill, normally on the mway its sits around 450 degrees. Last compression test about a year ago showed similiar readings on all 4 cyls with over 300psi. Question 2 - are 300Tdi cracked heads common? Are my cracks due to old age and thermal fatigue or overheating. The engine is on its 2nd set of injectors, I changed the 1st lot at 100k miles, this lot have done 65k odd. When i replaced the 1st lot, they looked fine and the new ones made no difference to running or economy. When I removed this lot, they had carbon deposits on the tips. This cleaned off with a petrol soaked rag, but no 3 injector tip is all corroded and I can only see 3 of the 5 spray holes in the end. Question 3 - What has caused the corrosion? I don't use supermarket diesel, only BP or Shell, and I change the fuel filter every year. There is never any water in it when I change it. So it looks like another set of injectors as well as a new head..... Quote Link to comment Share on other sites More sharing options...
simonb Posted June 12, 2007 Author Share Posted June 12, 2007 Back to top, now with pics... Quote Link to comment Share on other sites More sharing options...
simonb Posted June 13, 2007 Author Share Posted June 13, 2007 Well new head from Turners has arrived, complete with valves. Unfortunately I could only get one of the old injector clamp plate pins out of the old head, the others are corroded in. And guess what, they are back ordered with LR, not due in till 1st wk of July. Its been off the road 2 wks already. AARGH So quick call, to Turners on the off chance to see if they have any... Frida says she'll pop some in the post FOC. Excellent. Browsing on their web page I then see they all have BRAND NEW boxed Bosch injectors for £40 vs LRs £65 recon price or over £80 new. Another phone call to Frida and a set of injectors are ordered as well. Then a phone call to the dealers to cancel my order with them. 10 out of 10 to Richard and Frida! Quote Link to comment Share on other sites More sharing options...
western Posted June 13, 2007 Share Posted June 13, 2007 Hi Simon, 1.I know 200Tdi's have had gasket faults in the past I assume 300's have to seeing as it's almost the same engine, 2. had to replace my 200's cylinder head recently due to internal cracks, it was using water but not into oil, seems it was cracked into one of the valve chambers & getting burnt or vapourised. 3.probaly just down to heat or additives in the fuel or maybe the injector material was faulty. good to hear all the new parts are from a top quality supplier Quote Link to comment Share on other sites More sharing options...
simonb Posted June 13, 2007 Author Share Posted June 13, 2007 Hi Simon, 1.I know 200Tdi's have had gasket faults in the past I assume 300's have to seeing as it's almost the same engine, 2. had to replace my 200's cylinder head recently due to internal cracks, it was using water but not into oil, seems it was cracked into one of the valve chambers & getting burnt or vapourised. 3.probaly just down to heat or additives in the fuel or maybe the injector material was faulty. good to hear all the new parts are from a top quality supplier Hasn't urs done 237K miles though... Interestingly the Tdi's ally head internally looks similar to a series cast iron one - lots of metal, small waterways. Did LR use the same casting mold when they switched to ally heads? If you look inside a modern ally car head, there is lots of water ways, not much ally and lots of strengthening webs. Now a Tdi isn't a highly stressed engine, so are the cracks possibly a result of the thick metal around the valve seat and the thermal stress of one side being at 90 degrees and the other at 500? In a modern head with thinner metal, although the temp gradient is the same, it would be across less thickness of metal, leading to less stress.. Any thoughts? Quote Link to comment Share on other sites More sharing options...
western Posted June 13, 2007 Share Posted June 13, 2007 Hasn't urs done 237K miles though...Interestingly the Tdi's ally head internally looks similar to a series cast iron one - lots of metal, small waterways. Did LR use the same casting mold when they switched to ally heads? If you look inside a modern ally car head, there is lots of water ways, not much ally and lots of strengthening webs. Now a Tdi isn't a highly stressed engine, so are the cracks possibly a result of the thick metal around the valve seat and the thermal stress of one side being at 90 degrees and the other at 500? In a modern head with thinner metal, although the temp gradient is the same, it would be across less thickness of metal, leading to less stress.. Any thoughts? Yes mine has done a fair few miles LR made new casting moulds for the Tdi heads as the external surface is different as are the injector/glowplug locations, probably a coincidence that they look similar to Series cast heads. you maybe right about the thermal properties & temp gradients through the cylinder heads material. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted June 14, 2007 Share Posted June 14, 2007 Re your EGT readings - 620c is a bit low for flat out on a motorway hill - mine will go to 700c easily and eventually set off the alarm at 725c under those conditions (although at 5000 ft which may make a difference). My thermocouple is between nos 1 and 2 exhaust valves btw. We get lots of cracked 300tdi heads here, normally caused by overheating which itself is normally caused by a hose blowing. I have investigated the reason for this and it is mainly caused by the sudden decrease in coolant pressure which causes the coolant to boil. For example, 40% antifreeze increases the boiling point of water by only about 5 degrees, whereas 1 bar pressure increases it by another 25c. So when a hose blows the coolant will boil in the engine. If possible, the engine should not be instantly stopped when it overheats, rather idle it to circulate what coolant is left. Cracks between the valve seats are common, though sometimes the crack or porosity is not visible and only a pressure test will show it up. ps. The favourite hoses to 'blow' are the Disco heater hoses which are hidden behind the engine. AFAIK the Elring OEM gasket is unchanged. The TD5 has the fancy double steel gasket. Quote Link to comment Share on other sites More sharing options...
simonb Posted June 14, 2007 Author Share Posted June 14, 2007 My thermocouple probe is fitted to the EGR blanking plate. I've got a full width Intercooler but didn't tweak the fuel much to prevent potential cracked head/melted pistons/burnt valves - looks like I needed have bothered. Its never lost coolant pressure and never boiled up, so I guess its just bad luck. Anyway injectors and clamp pins turned up at 11am from Turners. I've just spent this eve getting the head torqued down and rocker gear back in. Hopefully normal service will be resumed over the wknd. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted June 16, 2007 Share Posted June 16, 2007 Maybe your EGT probe is a bit short so it is not in the gas flow. We fit EGT plobes to the EGR blanking plate but make sure that they are long enough to get into the exhaust flow. Nothing of this matters really becuause the temp is relative. I must add that new injectors have never seemed to fix anything on a tdi. LR stealers used to like to replace them because it was easy and got them a nice mark-up. And Bosch dealers can change the tips now and reset the springs inside for cheap. I changed my injectors and the engine was worse! Quote Link to comment Share on other sites More sharing options...
simonb Posted June 17, 2007 Author Share Posted June 17, 2007 Probe is about the length of a finger and curves round inside the manifold to be in the gas flow. Anyway its back together and it runs but its not over yet as the injector pump is raining fuel from the throttle spindle - see Int Forum for more details.... Quote Link to comment Share on other sites More sharing options...
simonb Posted June 24, 2007 Author Share Posted June 24, 2007 Probe is about the length of a finger and curves round inside the manifold to be in the gas flow.Anyway its back together and it runs but its not over yet as the injector pump is raining fuel from the throttle spindle - see Int Forum for more details.... Well thats fixed - see thread how to do it, and after 3 wks and between thunderstorms over the last few days, the Landy finally got back on the road yesterday afternoon spalshing around in the big puddles caused by yet another thunderstorm. It don't half feel weird driving that it again after driving round in a borrowed Eurobox for 3 wks.. Quote Link to comment Share on other sites More sharing options...
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