Opinion on a Td5 cooling thing pls

[Shackleton]

What conclusion would you come to if you encountered the following on a Td5:

Pressure gradually builds up in cooling system, but not until engine is hot. Top pipe firm/hard rather than rock hard, and not bulging.

Pressure is enough to force a weep of coolant out where the top hose meets the rad. Removing the pipe and reseating a number of times makes no difference - this is always the spot it weeps, but from different points in the joint each time it's reset.

Pressure subsides in normal time after engine is shut off.

No coolant is forced from expansion tank overflow / relief.

Head gasket is new. (Head tested, skimmed and diligently replaced less than 4k miles ago)
Water pump is new. (Non genuine but with expansion cap off from cold there's a strong and steady stream back into the tank)
Thermostat is new. (Genuine)
Expansion cap is new. (Genuine)
Rad is from 2012 (did suffer both HG failure and oil cooler failure in that time, and I believe prior to my ownership wasn't being ran with coolant but just water)

No fluids migrating.

System has been dismantled and flushed last week. Rad did produce heavy oily gunk, and had a thin coating of same visible on inside, but seemed to flush and back flush ok.

Heater matrix flows strongly.

Rad is hot at very top but mainly cold all over.

Temp stays optimal at all times, in fact while left idling with the heater on full and I was checking tyre pressures the thermostat closed and temp dropped back to 1/4. Ambient temp was your average October eve, although this Octobers been warm so even stranger.

Your thoughts or experience would be appreciated! I don't want to say what I think it is, I'm trying to decide whether to throw any more time or money in, or just walk. So looking for second opinions.

[Ally V8]

Sounds like a cracked head,was it pressure tested properly before the skim ? It may be cracked in an inlet port,(Pressurises during boost conditions) I've seen them go along the "seam" of the casting.Also tried welding them,all that happens is that the crack followed the weld... Some claim to be able to do permanent repairs,but they must have more than an ordinary Tig torch and pre heat kit to do that.

[Shackleton]

I'd go as far as to say the firm I got to test and skim the head are the best in Ireland. The engineer told me it held pressure perfectly but the surface was actually quite bad and that he'd had to take an estimated 6 thou off to get it workable.

I've heard of this inlet crack situation, and then the possibility of sniff tests not showing anything untoward. What a pain in the neck!

[Ally V8]

I've had more than one where sniff tests cam back negative,there were no external leaks,but unexplained and often non linear amounts used. You can only go so far before removing the head and having it pressure tested with the water in the testing rig almost at boil point.

I've just done a 99 Defender 90 TD5 which was using coolant with similar symptoms to yours.In this case there were obvious failure points around the fire rings into the coolant passages on cyls 4 and 5. Head needed a light skim,but it seems OK now.

If yours is cracked you have some serious decisions to make...

[Shackleton]

I'm fairly resolved already mate (thanks for the expertise) in that I find it interesting that the point of pressure seems to be on entering the rad. I've read that coolant can flow through the rad without actually going through the core. This sounds like it could be bull****, but then I don't know. I'm thinking that rad replacement is my only course before walking away. I'm not getting into stripping the head again. Really though I'm not even so willing to spend the money on a rad, but if I thought it was a likely culprit Id have no prob.

I thought I'd gotten on top of this pressurising but I just taxed the car today until the new year and after a long run the prob was back. It might be a case of just driving it until either it or the tax gives out

[dave88sw]

Just a thought but what if you replace that stupid spring clip with a proper jubilee clip? I really hate the spring clips, they never seem to seal properly unless all teh components are brand new.

[reb78]

The coolant hoses can delaminate somewhat inside. This allows a weep of coolant to travel up the cords in the rubber and out of the end. What does the coolant pipe look like around the area where it's weeping?

[Shackleton]

Good suggestions both, thanks Dave and Richard, I'll do both. I've already swapped out most of the bottom spring clips.

The coolant pipe looks and feels in good order (I have experience with delaminated rubber hoses, but hadn't thought of it). The cords were stained orange from coolant but I could visibly see it squeezing out between the pipe and the rad, plus after a few reseats of the pipe the cords are normal colour again so I don't think it's that.

The rad rings bells for me now. I had done about 8 flushes each with powdered dish washer powder, after the oil cooler burst / H/G went. When the scum stopped arriving in the expansion tank I then flushed a few times with water. Everything was fine, although it wasn't long before I noticed the pressure and leak at the top hose. At that point though it seemed intermittent. Sometimes it was there but 9 times out of 10 it wasn't. I don't know if dishwasher tabs are designed to congeal grease, but that'd make sense to me from what I've seen.

When I finally decided the rad had to come out the mayo in the bottom wasn't off white, it was chocolate brown and much much thicker, like barely willing to run and as if like I say the tabs had gathered it together and it was too thick to get past the thermostat. When I broke the bottom pipe this goop flicked out, and was evident in the old thermostat too. Top rad inlet was clean inside but a thin layer of this goop was evident as far as the eye could see in bottom of rad. I left the rad upturned over night, I had it sitting on a thick towel to protect my garage floor. In the morning there was a blob of this stuff about the diameter of the pipe sitting under the outlet on the towel. As in it didn't penetrate the towel at all!

So I flushed the rad, first twice with petrol then with numerous soapy water flushes, some left to sit. The petrol flush was disappointing in terms of not producing nearly as much oily residue as I expected. I can't overstate how viscous this goop was, the petrol didn't lift it from the plastic walls of the rad inside. So I'm thinking that between the P/O not bothering with coolant, and this thick goop in the bottom of the rad, it must be operating on severely reduced cores, even though it was a new rad not so long ago.

I'll put a few quid into an aftermarket rad asap (driving in the meantime) and let you know how it goes.

[Shackleton]

I have one last question:

Does anyone remember what proper flow through a Td5 rad looks like. It's been too long since I did a known good rad to remember. This time though the hose could fill the rad quicker than the rad could drain. Water pressure here is average.

[Mo Murphy]

I'm by no means an expert Shackleton but if it didn't come out as fast as it went in then wouldn't the rad eventually become pressurised and spring a leak or become an obstacle in the cooling system ?

Mo

[Boydie]

Mr Shackleton,(all honor to him of noble Irish lineage)

I'm guessing here from what has been written so far that the TD5 has the same (copulating inane) cross flow radiator arrangement as the 300tdi and forgive me if it hasn't but, if it has and the radiator is hot at the top and cold elsewhere then it's my educated guess that some previous owner has removed the baffle allowing the water to bypass 50% of the radiator on it's way back to the engine -- either that or the by-pass orifice hole has been enlarged to the extent that the baffle plate is of no value, the coolant flow will always take the easy route of least resistance.

The orifice hole, normally around 3mm in diameter is only there to allow air to escape to the top of the radiator and - eventually - vent into the header tank.

[Shackleton]

I'm by no means an expert Shackleton but if it didn't come out as fast as it went in then wouldn't the rad eventually become pressurised and spring a leak or become an obstacle in the cooling system ?

Mo

That's what I was thinking Mo, and a mech. I spoke to the other day (with only the symptoms to go on) was sure it was a blocked rad. The new rad arrived and I stripped the car today. I decided to run a wee experiment to see how much water the old rad would hold, against how much the new rad would hold - assuming it would be conclusive evidence that the capacity of the old one was greatly reduced. Guess what... if anything the old rad holds ever so slightly more than the new (what I get for buying a spurious "OEM" item. So I'm back to scratching my head. I'm now resorting to checking stupid things like route of the serpentine belt and thermostat fitment before I give up and presume that the head gasket has lasted less than a few thousand miles.

I'm guessing here from what has been written so far that the TD5 has the same (copulating inane) cross flow radiator arrangement as the 300tdi and forgive me if it hasn't but, if it has and the radiator is hot at the top and cold elsewhere then it's my educated guess that some previous owner has removed the baffle allowing the water to bypass 50% of the radiator on it's way back to the engine -- either that or the by-pass orifice hole has been enlarged to the extent that the baffle plate is of no value, the coolant flow will always take the easy route of least resistance.

It's a "copulating" mess Boydie

The Td5 cooling system is self purging so far as I've read, even if not, I don't think there's any sort of bypass plate, and I don't think my rad's anything other than standard anyway.

In my frustration I have uncovered what I believe is a mistake in the RAVE manual. Observe if you will - the coolant flow of a pre-EU3 Disco Td5: As shown the thermostat (once open) routes coolant that has been cooled by the radiator, back to the pump AND back to the radiator at the same time. I believe that the arrows in the pipe that leads downwards from the top hose to the thermostat should be pointing in the other direction. That is the main flow of coolant, that bypasses the rad until the engine is up to temperature. In this stage while my engine is warming the flow is fine, and it's not until full temp is reached that the pressure seems to build. Which points to the thermostat, but could a brand new LR item be duff!?

Also attached is the flow of the thermostat at varying points in the heat cycle that further illustrate coolant flow. (attached image is actually a K-Series thermostat but I believe they operate the same). Interesting and worth noting.

[Shackleton]

Thermostat in the wrong way round. What a spanner.

Looks like the RR is about to get a surprise new rad

[Mo Murphy]

Easy fix is always good ?

Mo

[Anderzander]

Excellent !

[Shackleton]

yeah phew

If the rain would just go away now...

[Mo Murphy]

It's supposed to rain, you're in Ireland ?

Mo

[GBMUD]

I seem to have arrived late at this party, and I am by no means an expert, but shouldn't the cap on the expansion bottle have some part in this story? It should hold back, from memory, 15psi, thus not allowing more than that pressure to build up in the system. Assuming that it is functioning correctly then it still points to a problem with the top hose/radiator spiggot.

If the head were allowing air into the system then one would assume it was a lot more than 15psi worth and the header tank should bubble and vent through the cap all the time.

Glad you seem to have found a solution.

Chris

[Shackleton]

Thanks Chris. As of a 15 mile round trip this evening all seems well. Will check the rad tomorrow to make sure it's getting an even warmth, but on first inspection the top hose is firm rather than hard. The thermostat was certainly the wrong way around so as far as the flow is concerned it was actually closing, so the pump was pushing against a dead end. It did about 800 miles like that but I seem to have gotten away with it. Fingers crossed.