Strange cooling issue

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DaveM-sport

DaveM-sport

Active Member
Posts
847
Location
Cork, Ireland
Even though not overheating at all and no white smoke or of any colour for that matter, my Defender seems to be developing a slight airlock. At times, the heater blows cold and then hot again for a moment but think this might have been down to a slipping drive-belt or faulty tensioner as steering was heavy too and it was worst for this at tickover or in traffic but perfect once revs rise and moving.

When stopped after use, can hear slight hissing under the bonnet by the expansion tank and heater matrix but other than that, it's driving perfect. Even when towing for a two hour round trip, it didn't go over 90 degrees once.

Would assume it could be a headgasket but then it's not showing real signs of it with very bad pressurization, blowing bubbles out the expansion tank or overheating when under sustained load.
 
Checked this morning to see if coolant level dropped and it was still around the cold mark in the expansion tank.
Opened the bleed screw then, and small few bubbles but coolant coming out nonetheless so level not down much.
Topped up the tank to get a steady flow again from the bleed screw and within maybe a 100ml or less even, it had a decent flow. Kept going and got a small bit more air before it started to really flow out well. Squeezed the heater pipes then to see if they were full and pushing coolant out the bleed screw so heater matrix should be full and no air trapped inside it. This was all done while engine off and cold as I've been doing it while hot and heater on and doesn't seem to be getting all the air out.

Not sure what's the better method as some say while running and heater on with engine upto temp and the workshop manual and others say while cold, then run engine upto temp and then check level again when cooled.

As the heater circuit is open either way when stat is closed and only diverts coolant when revs are over 1500 or so, I don't see why engine needing to be running and hot is essential really


As for the belt, it's a dayco belt that's on it but have noticed the alternator and tensioner seem to be nosed in towards the engine very slightly for some reason.

Will have to undo the bracket and see if it's seated correctly or put a shim under the front if needs be as the slight misalignment might be the cause of my belt and tensioner issue
 
I had silimier issues but my fuel was getting hot and the cooling lines ran from the heaters down to the fuel cooler ..there is a few thermostats placed in this engine

if you think its combustion gasses purchase a sniff tester I have seen heads with a slight crack that only open at a curtain temp

the belt tensioner maybe leaning over due the centre bush worn out but this wont create an air lock
 
Yea, it's only very slight airlock or else I just didn't get the last of the air out of the system upto now. Going to do a pressure and sniff test to be sure though although on diesel, these aren't totally fool proof of thinking there's noting wrong either if the results are clear.

Tensioner bearing is fine, it seems the complete alternator and tensioner unit is slightly off line.
 
So looks like it's a cracked head or gasket anyway.

Took it for a short drive into town today after bleeding it completely as rave says.

Was fine into town, could still hear hissing from expansion tank and heater matrix area when stood by the wings.

Cam home, was parked for 5 minutes and then out again. This time, I didn't track 3 miles before it got badly airlocked and heat shooting up to towards 100 degrees.

Left cool, bled it again as had coolant with me just in case something happened. Another 2 miles and overheating again.

Disconnected heater matrix and looped the pipe from expansion tank to the pipe along the exhaust manifold as there was no coolant on return pipe from heater core in case blocked even though only a week old as well as rad.

Got less than a mile with heater matrix bypassed before temp shooting up again.

There's no pressure at all in the system as expansion cap just screwed off fine but it looks like its blowing out the cap as under the bonnet us covered in coolant from the expansion bottle. Took 2 or 3 litres to fill to bleed again so just drove it into a neighbours yard then rather than chancing it home again.

New AMC head I think and be done with the thing!
Kit hope it's not a cracked liner as couldn't deal with another bare engine rebuild again after only doing it less than 1500 miles ago.

Just wondering would the head have been weakened with the the skim it got during the rebuild. Some. Say you can't skim them, some get on fine but wonder would a tuned engine with probably maybe higher CR with new bigger pistons and decked block be just that little bit too much.

If a new head cures it even though awful hassle and cost, I'll be happy to have it right. Just hope it turns out the liners aren't able for the. 5mm overbore and one is after cracking.

Going to pressure test the system tomorrow anyway just to be sure
 
sorry to hear about that
I would also suggest replacing the head bolts if you remove the head ..there could be a slight possibility that there stretched resulting in a warped head

allow your engine oil to settle and drain you may get water out ..this could be a liner or coolant is escaping past the rings over night depending if the crack closes when cool

there is a way to check the liners but you will have to remove the sump oil pump and stiffener plate ..pressure check cooling system and check all liners to make sure they don't drip you will have to manually turn engine over other wise tear it down and visually check
I highly doubt it its going to be a liner though
 
Yea, will replace all the headbolts again. They were all done anyway as well as new rod and Mains bolts when I rebuilt it not long ago.

johnlad said:
is the water pump working correctly
Click to expand...

I'd imagine it is as it's putting a steady stream out the bleed screw when removed when running in a fountain 6 inches or so high. When engine off, will just overflow depending on how full the expansion tank is.
 
Last edited:
With expansion cap off on tick over, get someone to rev engine, you should see the water swirl in expansion tank
 
Yep. with the cap off, can see the small return pipe filling back into the tank.

Checked this morning and no real coolant loss of where I had it yesterday when stopped it as it started to get hot again.

Topped it up and bled it again and tried a genuine expansion bottle cap as one on it was a Britpart one in case it was the problem.

Was fine for about 5 mins and just drove it up and down the road outside my shed.

Then once the temp reached 86 or 87 degrees, it just continued to climb so shut it off again.

Checked the top rad hose again and bleed screw and full of air again so looking like I definitely have a headgasket issue at the least :(
 
DaveM-sport said:
So looks like it's a cracked head or gasket anyway.

Took it for a short drive into town today after bleeding it completely as rave says.

Was fine into town, could still hear hissing from expansion tank and heater matrix area when stood by the wings.

Cam home, was parked for 5 minutes and then out again. This time, I didn't track 3 miles before it got badly airlocked and heat shooting up to towards 100 degrees.

Left cool, bled it again as had coolant with me just in case something happened. Another 2 miles and overheating again.

Disconnected heater matrix and looped the pipe from expansion tank to the pipe along the exhaust manifold as there was no coolant on return pipe from heater core in case blocked even though only a week old as well as rad.

Got less than a mile with heater matrix bypassed before temp shooting up again.

There's no pressure at all in the system as expansion cap just screwed off fine but it looks like its blowing out the cap as under the bonnet us covered in coolant from the expansion bottle. Took 2 or 3 litres to fill to bleed again so just drove it into a neighbours yard then rather than chancing it home again.

New AMC head I think and be done with the thing!
Kit hope it's not a cracked liner as couldn't deal with another bare engine rebuild again after only doing it less than 1500 miles ago.

Just wondering would the head have been weakened with the the skim it got during the rebuild. Some. Say you can't skim them, some get on fine but wonder would a tuned engine with probably maybe higher CR with new bigger pistons and decked block be just that little bit too much.

If a new head cures it even though awful hassle and cost, I'll be happy to have it right. Just hope it turns out the liners aren't able for the. 5mm overbore and one is after cracking.

Going to pressure test the system tomorrow anyway just to be sure
Click to expand...

You haven't got a pin-hole leak on a pipe that pees out and evaporates ? ... Only does it under pressure, closes when cooling and contacting ?

Might need to pressure test to be sure or dust it with good old talc ...
 
Wouldn't think so as it's building pressure and getting too airlocked to be an external leak like that.
Just got ****ed off with it today anyway and pulled the head off it altogether.

Headgasket doesn't show any signs of failing after a quick look at it. Dropping the head in to be tested in the morning and will go from there.
In one way, aside from the cost obviously, I'd be almost happy the head is cracked as then would know what the problem is and could be sure a new head would sort it.
 
Head checked and result was all fine anyway so kinda stumped now other than block in trouble! :(

Might get a plate of aluminium maybe and use as a torque plate with a rubber between it and the block and pressure test it on its own to check it before go to the hassle of pulling it all out and stripping it down again
 
So after another look at the block as was rushing before the weekend to get the head off to get it tested before the machine shop closed... And probably missing it with the onset of a cold lol.

Had a proper look at both sides of the gasket and it's blowing the underside from cylinder 1 out to the front water gallery behind the timing case.

Cylinder 1 is also showing signs of detonation again almost exactly like they did which caused my engine rebuild in the first place!!! Was told the injectors were ok but obviously the place I used doesn't have a clue.

Almost lucky in one way it developed cooling issues as could have found out through blown by or missing again like before if I didn't get a chance to buy new injectors soon!
 

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People think TD5 injectors are bomb proof... Well I no 3 people to have suffered injector failure... Myself included... Best of luck

Cheers
 
Far from bombproof lol.

The engine **** itself last time from missing and blow by and had very bad detonation on cylinder 5.

Got two sets and and a set of black ones. not sure how I ended up with spare black ones but that's another strop I suppose lol)

Was told the green ones are fine albeit flow was slightly down but still usable. One of the black ones was completely bust so he reconditioned those. Said he couldn't do anything with what green ones for some reason and spent nearly a week "finding out" if the black ones could be used on my engine.

I had my doubts but kinda left him at it as I'd imagine he knew best as doing injectors everyday. When got them back, I just checked myself if they are interchangeable when was fitting them and first page on Google even told me you can't and why with the plungers different etc.

Had no option then other than to use the green ones that he said were usable until I was able to buy a set of new ones for it for peace of mind.

As usual should have checked stuff myself rather than expect to trust somebody that's suppose to know these things!

Very lucky my piston isnt damaged and it's just carbon build up after giving it abit of a clean after I took the photos.

New headset and bolts on the way anyway and will get a new set on injectors and hopefully it'll be good to go :)
 
15P. I know the 15P injectors can be used in the 10P alright but not the other way around.

Didn't know this for sure when was getting them done the last time of course.
Not sure how I ended up with spare black injectors unless they got mixed up when I had left some spare bits at my friends garage that's an LR specialist
 
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