What the hell is going on??

[TimR]

In recent weeks I have done some major work on my 1986 90 NAD. Firstly I changed the head for one from a less worn engine (it was easier than changing the valve seals) the other thing was to replace the radiator that was leaking for a heavy duty one (I also changed the oil, topped off the fluids etc). However, since those changes it has started doing something very odd when the engine gets hot (after about 10 minutes driving) the oil light comes on at low revs and the engine gives a shudder and tries to stall (when you take your foot off the accelerator when pulling up to lights or waiting at a junction for example ). If you turn the engine off and try restart it will barely turn over (as if the battery is flat) but you can feel the engine shake with the effort of moving the pistons in the block but it wont start again until you give it 10 minutes to cool down.

Its clearly seizing when hot but I cant see why. There seems to be plenty of oil splashing around when you take the rocker cover off, the temperature gauge doesn't pass half way, there is plenty of coolant and the system pressurise - there is a bit of play in the water pump but nothing major and the radiator is hot with no cool spots . There is also plenty of good quality new oil in the engine.

There is nothing to suggest the head gasket is faulty and it was double checked to make sure it was on the right way. There is no mayo in the oil filler, its not loosing water, the radiator I fitted was a lot chunkier than the old one but it very good condition. There was a slight difference in the location of the pressure switch on the newer head but it had come out of a vehicle that had done 100K miles less than mine.

Anyway, that was a few weeks ago. Today, simply because I wanted to rule out a damaged head) I striped it down again and put the old head back on ( after lapping the valves, changing the seals etc). I re-examined the head gasket to make sure it wasn't blown or snagged (it was fine) and put yet another head gasket on. I also took the water pump apart and examined it and that to was fine. Torqued the head up, double checked everything, started he up - first flick (she really does run sweetly) gave her 20 minutes to get good and hot.... and no change.

Of course it simply be coincidence that the oil-light problem started just after I did all the work but again, what could cause this? If its the oil pump wouldn't the the oil light also come on at higher revs?

I have mentioned it to others LR owners, talked to 2 mechanics and they just look perplexed. I still haven't ruled out the possibility that I have done something really stupid but I just cant see what could cause this... so I'm hoping someone here will have some ideas.

I'm determined to solve this puzzle !

Tim

[Dave W]

Overheating can cause the oil light to come on with the relief valve sticking open and dropping oil pressure.

Maybe the new head has a blocked or mismatched waterway ?

[RILEY]

HI just a couple of thoughts (probably stating the obvious) Valve clearances ok ,injectors ok , fan working ok (air flow thro rad?) you will need to do an oil pressure test Hope no perm damage has been done to the bores

[TimR]

As I say I have changed the old head back but to be honest it was probably fine, and valves, injectors fan etc etc just fine. The bores seem to be fine as well...

[dirkthe1]

if the rad is now bigger, there is the right aount of fluid in it now? not trying to insult you, just know some of the stupid things i do!

[David Sparkes]

Overheating can cause the oil light to come on with the relief valve sticking open and dropping oil pressure.

Maybe the new head has a blocked or mismatched waterway ?

Picking up on this, I see you have now tried both heads, and now experience the same 'seizing' problem with both. Can you compare the head-gaskets you have used with the original you took out, or against the 'newer' head (now removed) to see if a water passage way is being blocked?

Cheers

[TimR]

When I put the new rad in I flushed and refilled the system and of course I had to drain the block today when I did the head - but I topped it off..

The head gasket was just fine - no obstructions blows or rough-spots.. and the heads were indeed identical..

[Les Henson]

If the engine had been trying to seize, then there would be marks on the cylinder walls (usually piston-to-bore seizure is the first thing with engine overheat). There may be pick-up marks (alloy from the piston transferring to the bore wall through friction heat).

If the oil pressure relief valve was stuck open, then maybe there isn't enough oil flow to lubricate the engine properly, so possibly the crank is the problem. I would be inclined to drop the sump and remove the big-end caps and what main bearing caps you can get off with the engine still in situ (3-of them I think). If the bearing shells had been trying to seize, then they would have transferred phosphor bronze onto the crank pin (journal), and be easily noticeable).

Oil light flickering makes me suspect an oil and not a coolant problem.

Les.

[TimR]

If the engine had been trying to seize, then there would be marks on the cylinder walls (usually piston-to-bore seizure is the first thing with engine overheat). There may be pick-up marks (alloy from the piston transferring to the bore wall through friction heat).

If the oil pressure relief valve was stuck open, then maybe there isn't enough oil flow to lubricate the engine properly, so possibly the crank is the problem. I would be inclined to drop the sump and remove the big-end caps and what main bearing caps you can get off with the engine still in situ (3-of them I think). If the bearing shells had been trying to seize, then they would have transferred phosphor bronze onto the crank pin (journal), and be easily noticeable).

Oil light flickering makes me suspect an oil and not a coolant problem.

Les.

Thanks Les

So you are going for the not related to the head change link? But wouldn't there also be problems at higher revs if was related to the pump assembly(where I think the valve is located)? Also if the engine is overheating wouldnt it be a case that the oil viscosity would change causing the low pressure warning light (my reasoning).

t

[Les Henson]

The oil would become thinner, but (assuming the pump is ok), then pressure wouldn't be affected that much I think - the pump will do it's job regardless. As you have put the old head back on and still have the same problem, then it may be it's just an unfortunate coincidence. If your problem was coolant related, then the radiator hoses would become rock solid and the expansion tank cap (radiator cap), would open and coolant would be expelled from the overflow pipe. Your temperature guage would also indicate excessive coolant temperature. If the temperature guage has only risen a small amount, then this could be attributed to heat from the oil getting too hot and raising coolant temperature a small amount.

Altered oil flow can be attrbuted to a few things - leaks, not enough/too much/wrong/ oil, pressure relief valve stuck open/closed/weak spring, oil strainer partially blocked with debris (usually over-enthusiastic use of silicone sealant, bits of old gasket, carbon particles).

For me, inspection of the crank journals would be the next step.

If you suspect a restriction on coolant circulation because of perhaps a possible blockage, then a laser temperature meter is very useful for detecting temperature chages throughout the cooling system (about £50 for one though).

Les.

[TimR]

That's good reasoning - thanks.

I did take the sump off and take a look at the strainer, and it was clear, but at the time assumed that the problem was related to the head-change so didnt got any further (though there was some phosphor-bronze in the sump due to a couple of damaged [now replaced] followers). I should add its got 2 mechanics (one a head land rover, the other a jobbing mechanic of 25+ years stumped - though without actually investigating the symptoms) so perhaps it just one of those bloody awkward coincidences..

Oil pump was the next thing on my list but It selling time and I really don't want to go down the rout of a partial rebuild.. but then needs must..

thanks again

t

[V8CAMEL]

That's good reasoning - thanks.

I did take the sump off and take a look at the strainer, and it was clear, but at the time assumed that the problem was related to the head-change so didnt got any further (though there was some phosphor-bronze in the sump due to a couple of damaged [now replaced] followers). I should add its got 2 mechanics (one a head land rover, the other a jobbing mechanic of 25+ years stumped - though without actually investigating the symptoms) so perhaps it just one of those bloody awkward coincidences..

Oil pump was the next thing on my list but It selling time and I really don't want to go down the rout of a partial rebuild.. but then needs must..

thanks again

t

seen this before where the strainer was touching the bottom of the sump because the sump was distorted. look for a circle mark on the inside of the sump

[TimR]

Thanks for the input everyone. Ill keep the thread updated.

[TimR]

**UPDATE**

Evening all,

So, sump off, oil pump out, caps off...

The strainer looks clear, the sump isn't interfering with the flow. Movement around the relief valve seems fine (I though there was supposed to be a ball-bearing, not just plunger in there though) the spring is still pretty 'springie' and the gears look to be in good condition. The bearings, journals etc look OK for a engine with 160K (pics included).

Tim

[Les Henson]

1st pic - shell still has the coating, but looks bad to be honest. 2nd one has gone throught the coating to the copper plate underneath. If it's a picture of the top half of a big-end shell, then it's pretty normal wear really.

Pics of main shells?

Les.

[TimR]

Hi Les,

The the shell with all the coper is No1 main baring shell. 4 looks exactly the same. I suppose it is pretty goosed, but would it cause the symptoms as described?

Tim

[Les Henson]

Worn Main or big end bearings like that may well cause low oil pressure, so might cause the flickering oil pressure light. If all main bearing shells are like that I'm surprised there wasn't a rumbling noise when the engine is running, What are the big end shells like?

Les.

[TimR]

Les - pretty much all like the shell in the above picture. Shown are [top] big end No 3 - [bottom] main No 1.

As I mentioned, apart from the oil light and what appears to be a seizing in the bore (when you try to restart when hot) which started immediately after the head work she runs very well. Not particularly smoky, not particularly noisy, pulls well (apart from the usual inadequacies of a 2.5 NAD) and after a 10 count with the preheaters, starts first flick.

As for the condition, she has done 160k without any work so I'm not too surprises that there is wear. If I hadn't bought a 300tdi in November I would be looking for a 2 or 300tdi transplant for her now rather than just decided to sell her.

[jonost24]

Hi All, I had a similar problem on my 1700 x-flow when I built my Westfield. Most of the time it would start ok,

then it would barely turn over, indicating something like a flat battery, to a point where it almost felt like it

was seizing up. I think it was my own fault because I had "tinkered" with the dizzy i.e. trying to find its

"sweet" running spot by twisting the dizzy in the block. This, I think had an adverse effect, by retarding or

advancing the ignition (I forget which) to a point where I think fuel was going in, but the spark was miles out.

I reckon in the end it was compressing fuel, but not burning it (a form of hydra-locking maybe, I don't know)

Fortunately I had a mate who is a whizz with petrol engines, he came over, sorted it, then it ran and started

sweet as a nut, hot or cold.

I've just thought...... its diesel isn't it? , fires on compression I'll get me coat

[TimR]

I've just thought...... its diesel isn't it? , fires on compression I'll get me coat

LOL!

[gruntus]

Apart form the crank bearings being worn whatabout the camshaft bearings?

Seem to remember when rebuilding my 200TDi being advised to check as worn/out of place cam bearings can result in low oil pressure?

Cheers

G

[western]

that would be number 4 cam bearing moving & closing off it's oil feed hole, I checked mine a while ago, did it this way, remove the lift pump & the cover plate it attaches too, then with a good strong light look rearward at the cam bearing, if the bearing has moved you will either see a lip protruding forward of the engine block casting or have a gap under the camshaft bearing if it's moved rearwards, hopefully there won't be either, as to fix it a total engine strip, new bearings fitted & line reamed to suit the camshaft bearing surfaces size.

I keep my fingers crossed that it's all OK.

[david s]

did you adjust the fuelpump after changing the timing belt...?

[TimR]

Looks like the bearing are where they should be and the timing belt wasn't touched... Cheers though

[western]

that's good news, means less expense.