2.5 DSE - Cracked head without overheating ?

About 6 months ago my DSE had a head gasket failure (lots of white smoke and temperature in the red). The head was removed, pressure tested and checked for warpness and was OK, according to the indie and the specialist that did the job.
After getting my Range Rover back it kept on using some coolant but I never gave it much thought because it used to loose some coolant before too, but nothing serious.
Today, after a 100km trip, the expansion tank was empty and I had checked the level before departing. It never overheated. On the way back I plugged in the Hawkeye and kept checking the temperature. After a long hill, the engine temperature reached 104ºC, but the coolant dial was still a little to left of middle position, as usual. Upon reaching my destination I checked that about one liter of coolant was expelled from the tank (I put a plastic bottle on the end of the pipe so I know how much was released).

So, I'm thinking about changing the expansion cap and header tank (just in case) but what is bothering me is a possible head problem. Is it possible that I have a cracked head that is pressuring the system but, at the same time, not enough for it to overheat ? Engine temperature is always spot on 85ºC except on hills where it climbs a little.. (or a lot on very big hills, as explained above).

Change the Cap and see what happens...

The cap is there to maintain system pressure as the boiling point increases under greater pressure - not sure what the caps are rated at but there is a number embossed on top giving the rating.

If the cap is duff, it won't hold system pressue and the water will boil, releasing as steam out of the overflow or from the cap pressure release vents....this will cause rapid expansion of the coolant, only for that to be expelled too....

If the engine performs faultless, the gauge is in the middle and there are no other overheating signs - my bet is on the Expansion tank cap causing the coolant to boil at a much lower temperature than system design...hence loss of coolant due to boiling, but no overheat on gauge.

Air in the system can cause localised boiling which will expell water from the expansion tank but SV8 is probably on the nail. Make sure the cap is down tight, mine becomes tight as if it's fully down, then will turn another 2 turns before it seals.

also - use an airline to blow through the radiator bleed pipe - mine was blocked and so wasn't working!

quick blast with 190 psi shifted it

Ok, so I got a brand new cap from Landrover and replaced the header tank with a used one, just in case.
Took it up a very big hill, pushing down the pedal on 4th (mine's a manual) and just as I got to the top of the hill the gauge went up all the way to the end of the white section. Engine temperature was reading 119ºC!! It threw out some coolant, around 30cl I'd say.

All the items in the cooling system are less than one year old. New original termostat, new water pump with the metalic blades, radiator from Allmakes Pro line (manufactured in the Netherlands), OEM viscous fan reboxed by Allmakes. I can't help thinking that I have a cracked head that only shows under heavy load...

mcapinha said:

Ok, so I got a brand new cap from Landrover and replaced the header tank with a used one, just in case.
Took it up a very big hill, pushing down the pedal on 4th (mine's a manual) and just as I got to the top of the hill the gauge went up all the way to the end of the white section. Engine temperature was reading 119ºC!! It threw out some coolant, around 30cl I'd say.

All the items in the cooling system are less than one year old. New original termostat, new water pump with the metalic blades, radiator from Allmakes Pro line (manufactured in the Netherlands), OEM viscous fan reboxed by Allmakes. I can't help thinking that I have a cracked head that only shows under heavy load...

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I would still bet on a cooling system problem, RAD, stat, viscous or pump.
New means nothing these days

Thanks for your input, at least it gives me some hope. The last thing I replaced was the radiator because the older one broke near the water intake tube (seems common). I guess I'll start by looking at that.

mcapinha said:

Thanks for your input, at least it gives me some hope. The last thing I replaced was the radiator because the older one broke near the water intake tube (seems common). I guess I'll start by looking at that.

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Check the RAD gets hot all over and that the baffle is in place in the centre of the header tank. Maybe check the viscous first or do the aircon fans mod

What's the best way to check the presence of the baffle ?
I've tried to feel if it was getting evenly hot but I couldn't. Next weekend I'll take the fan guard off and I'll drive it for a bit to check if the rad is OK.

Upon further inspection, my radiator is from Nissens. Are these known for being of bad quality ?

I have a nissens had mine a year now all seems ok if that helps , a ball bearing swished from side to side in the empty rad will indicate weather you have a baffle in place .

I've been thinking.. as I posted in another thread, I've been running my DSE without the heatshield that goes over the exhaust manifold. Since there's a metalic water tube directly above the manifold, could the absence of heatshield cause the water in this tube to boil and cause my coolant loss/overheating problem ?

i never had a heatshield on mine and have pulled some very heavy loads without ever heating

The overheating problem seems to be getting worse: I took it for a small run in the highway and after 3kms it was already overheating. Since I had planned to check the radiator after this run, I had my IR gun with me and measured 95ºC on the plastic top of the rad and 25ºC on the bottom one.
Prior to my run I had removed the two hoses and tried to pass a hard metallic wire from one of the rad openings to the other. Since I succeeded in this and after taking temperature readings from the top and bottom of the rad I can now safely conclude that this Nissens radiator doesn't have the baffle and needs replacing

One thing that bothers me is how quickly it overheated this time.. since I hadn't messed with nothing in the cooling system I can't understand why it went into the red on such a short run when previously I could drive it for 100km and it would never overheat (just **** some coolant out)...

May be now you have a air lock in the system where you have taken hoses off???? I would say replace every thing but you say it's all a year old its worth taking t/stat out and checking wont cost you any thing same as water pump just new o rings for you to be sure . Mine uses water looses about half inch every so often no white smoke no head probs had it checked no water on floor all parts fairly new but it don't over heat like I said check pump and t/stat

mcapinha said:

The overheating problem seems to be getting worse: I took it for a small run in the highway and after 3kms it was already overheating. Since I had planned to check the radiator after this run, I had my IR gun with me and measured 95ºC on the plastic top of the rad and 25ºC on the bottom one.
Prior to my run I had removed the two hoses and tried to pass a hard metallic wire from one of the rad openings to the other. Since I succeeded in this and after taking temperature readings from the top and bottom of the rad I can now safely conclude that this Nissens radiator doesn't have the baffle and needs replacing

One thing that bothers me is how quickly it overheated this time.. since I hadn't messed with nothing in the cooling system I can't understand why it went into the red on such a short run when previously I could drive it for 100km and it would never overheat (just **** some coolant out)...

Click to expand...

Maybe as simple as the baffle just slowly falling over, now it's flat after you prodded it with your wire

Ps are you sure the top hose going into the head is not getting hard ??

defender300td1 said:

Ps are you sure the top hose going into the head is not getting hard ??

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Pessimist

A cheaters guide to checking water pump flow is to take air bleed pipe off radiator end and you can see it pumping out in time with pump only when cold tho!!!!

Datatek, I'm sure the baffle should be hard enough to sustain a little light proding ? Also, I didn't do any extra force, the wire (an unfolded metallic hanger) just slid through from one side to the other.

Defender30td1, The hoses get hard but not stone hard. After a long run I can still squeeze them a little bit, about 1 or 2cm, I'd guess.

Tomorrow I'll try taking the bleeder tube out and check if there's some coolant flowing, upon cold startup. Either way, I'm thinking about removing this rad and getting a new one so I'll end up checking the water pump and thermostat too.

Since I have the water pump with the metal vanes, what can go wrong with it, apart from bearing failure (of which I see no signs) ?