Maverik Posted May 20, 2021 Share Posted May 20, 2021 So got a situation which has got me a tad perplexed. Defender 200tdi - running VNT turbo a few fueling tweaks here and there but generally standard. So running with the VNT she's running at a higher "boost pressure" of up to 1.3 bar (dictated by the how the turbo is set up from "factory") - oil temp runs a fair but hotter then with the standard turbo - i.e. 60mph motorway run with 15 degree ambient temp you get oil temps of about 100-110. which equates to water temp of about 91-92 degrees. I was running standard rubber coolant hoses up until last Autumn where oddly after 1 standard run out to a friends I noticed that a number of various coolant hose connections had just started to leak coolant (I think I found 3 separate leaks). - I figured they where original hoses so was time for a change - I fitted a expensive set of Silicone hoses and have been running since with them. What I've found is after a decent run - you check the engine and all the water hoses are rock hard and the water in the bottle has risen by a good 30-40mm. So leaving to fully cool down (stone cold) the water level mostly returns to the correct level, but the coolant system still can hold a good bit of pressure, on squashing the top hose it feels like the hose is empty of water, on popping the thermostat cover off - this has been confirmed. I've fitted a thermostat cover that has an AC sender in it so effectively I can use it as a bleed point from the highest point (a bit like a 300tdi) - I'm still getting air coming out the system, which I find a little odd. I didn't have this issue when I had the rubber hoses fitted. The head was overhauled by turners a few years ago with new genuine headgasket etc. water is clean so I'm not really suspecting my head gasket. I'm not overly concerned as such as I'm not getting any overheating, but I just find it a little odd there appears to be so much air in the system. Slightly different direction but related - I've been playing with the idea of fitting an independent oil cooler to take some of the load off the radiator, but at the same time I noticed my radiator core was looking a little perished or maybe fitting an Allisports rad... Thoughts welcome. Mav Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted May 20, 2021 Share Posted May 20, 2021 6 hours ago, Maverik said: The head was overhauled by turners a few years ago with new genuine headgasket etc. water is clean so I'm not really suspecting my head gasket. Unfortunately air in the coolant system shouts head gasket type issues to me. Just because someone's done some work on the head and fitted a genuine head gasket (whatever that actually means) it doesn't mean that combusion gasses are not leaking into the coolant system somewhere. Why did you have head work done before? The leaking coolant pipes you mentioned, did they cause the engine to overheat and was this the reason for the head work? Quote Link to comment Share on other sites More sharing options...
Wytze Posted May 20, 2021 Share Posted May 20, 2021 8 hours ago, Maverik said: What I've found is after a decent run - you check the engine and all the water hoses are rock hard and the water in the bottle has risen by a good 30-40mm. Hoses getting really hard, does make you think about a compression leak in to the cooling system. Quote Link to comment Share on other sites More sharing options...
cackshifter Posted May 21, 2021 Share Posted May 21, 2021 Maybe you could test the coolant of combustion gases with one of those testing kits before assuming the worst? I am wondering if the hoses leak very slightly, I have a set that does, never amounts to a drip but can sometimes see traces of dried anti-freeze. This on a 300tdi with VNT that tows, so not entirely dissimilar ( I do have a 4 core rad though). Oil temps are interesting. Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 22, 2021 Author Share Posted May 22, 2021 I'd think head gasket, but it wasn't acting like this prior to fitting the silicone hoses. I did all the work, turners overhauled the head. I only did the head last time as I wanted the valve stem seals done and I suspected one of the core plugs to be weeping on the rear of the head. There no obvious indication in the water tank of an exhaust leak - I.e no wierd smell or oil/contamination in the water. I've no overheating issues, never have on this engine. I've got a Madman ems2 fitted so I can reasonably accurately see what's happening with verious temps and pressures. Temperatures don't appear to be divergent in the way that you slow down etc then temps come down pretty quickly. It's an old worn engine so having the engine run with the vnt at higher boost could have pushed it over the edge, it just seems not quite consistent with just a head failure. Good feedback though, need to have another look, might try test the coolant too! Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 25, 2021 Author Share Posted May 25, 2021 Ordered a chemical test kit today - hopefully should give a definitive answer! Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 25, 2021 Share Posted May 25, 2021 The system pressure goes up with temperature, so I wouldn’t be concerned about hard hoses when hot. If the rad is looking tired, you could have a pinhole leak that is letting the system draw air in as it cools. The other thing to check is the expansion tank and hose - make sure they’re clear and leak free, and that the cap is functioning correctly with its valves. Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 25, 2021 Author Share Posted May 25, 2021 18 minutes ago, Snagger said: The system pressure goes up with temperature, so I wouldn’t be concerned about hard hoses when hot. If the rad is looking tired, you could have a pinhole leak that is letting the system draw air in as it cools. The other thing to check is the expansion tank and hose - make sure they’re clear and leak free, and that the cap is functioning correctly with its valves. Another good shout, I did wonder about the caps wee valves I know they can get a bit gunked up, I'll get that checked out too. Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 25, 2021 Share Posted May 25, 2021 I had similar issues on my RRC 300Tdi, drawing air into the thermostat housing. It was the Y- piece that joins the expansion hoses from the thermostat housing and rad to the single hose to the expansion tank that was bunged up. I had thought it had valves in it, given the exterior shape, but it was a simple three way connector. Once that was cleaned, the problem never returned. I don’t think the 200Tdi has such a connection (my 200 being a Series retrofit, I can’t be sure), but any blockage of the expansion system would likely cause the same results. 1 Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 29, 2021 Author Share Posted May 29, 2021 Got a chemical test kit and popped it on the truck yesterday and it didn't indicate any combustion gas present - evidently it's a pretty reliable test. I also had a look about at the cap, it's one of the one with a level sender on it, looked ok. Went for a drive today and popped the bonnet after a decent run and the tank was pretty much full with only a small air gap - so I've ordered a new cap. It's obviously not holding its own, I thought you could dismantle the cap - the black ones I think you can to get in and clean the small relief valve and vac valve. So I gave it a good soak and blasted it with some water see if it washed any dirt out of it. Hopefully will improve it to get me bye until the new unit appears. Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 30, 2021 Share Posted May 30, 2021 The idea of the expansion tank is for it to fill when the coolant is hot, rather than dump it overboard. So, seeing it nearly full is normal. The question is why is it not siphoning back into the rest of the system as it cools? I think it is either that cap having blocked inward relief valves, a pinhole leak elsewhere or a blockage in the small hose between rad top and tank. Quote Link to comment Share on other sites More sharing options...
Maverik Posted June 1, 2021 Author Share Posted June 1, 2021 Yeah, I've been overthinking as per usual - I managed to borrow a replacement cap yesterday and its sorted the issue of rising coolant in the reservoir - which is the no brainer - if there is a leak there then the air bubble wont be sustained. - hard hoses I'm fine with, the system is meant to operate at ~1 bar. I had a better look at my radiator the other day and its pretty rough - a tad worse than I initially thought so I've got the radiator booked in for a re-core. Once done I'll have a concerted effort to bleed the system properly. Quote Link to comment Share on other sites More sharing options...
Peaklander Posted June 1, 2021 Share Posted June 1, 2021 The expansion tank must work in the same way as the pressure vessel in a domestic central heating boiler. They use a charge of air pressure on one side of a diaphragm to push against the water on the other side. As the water volume expands with temperature, the air gets squeezed and the pressure rises. At ambient temperature though, the boiler water remains pressurised, due to that initial higher charge pressure, whereas the engine coolant returns to atmospheric pressure. Quote Link to comment Share on other sites More sharing options...
Maverik Posted June 24, 2021 Author Share Posted June 24, 2021 A wee update - so I changed the coolant cap with a new aftermarket thing and I'm still getting a "filled" up reservoir and a very empty top hose. I've had a good inspection of the reservoir and it doesn't look cracked or split - I had a good pod, poke and squeeze when it was under pressure and I got nothing to indicate it had a problem I've got a new radiator now ready to go in as the present one is looking decidedly rough, will put new coolant in her too and give the system a flush. Quote Link to comment Share on other sites More sharing options...
Popular Post Maverik Posted June 28, 2021 Author Popular Post Share Posted June 28, 2021 So a positive update from over the weekend. The points above that snagger talked about the small air bleed pipe on 300tdi's got me thinking. And on Saturday I had a small epiphany. 200tdi don't have the same "auto bleed" hose off the thermostat housing - but they do have a small pipe that comes off the drivers side top of the corner of the radiator... To re-iterate - this problem only started when I had installed a new set of radiator hoses - logical deduction would point to a hose problem or a coincidence of something else happening! - anyways I went and got the old hoses I'd kept just in case and I found that the original small radiator bleed hose was a good 100mm shorter than the new silicone one I had installed, so I cut down the silicone hose to the same length as the original - the effect is that there is less catenary in the hose which I believe initially (with the longer hose) was stopping the radiator from self bleeding back into the reservoir. Well I had a long hard run on Sunday and she behaved just as she should no tank filling etc. so problem solved. Red line being where the hose was until I shortened it. 6 Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 28, 2021 Share Posted June 28, 2021 Glad it was a cheap and simple job in the end. You can imagine how difficult it was for the rad to push air that far down against coolant in that hose before it could escape upwards into the tank. I haven’t paid close attention to the original hose, but I’d assume it’s made with a 90 degree bend in it to keep the bulk of it as close to the level of the rad top as possible. 1 Quote Link to comment Share on other sites More sharing options...
western Posted June 28, 2021 Share Posted June 28, 2021 Similar lay to mine 2 Quote Link to comment Share on other sites More sharing options...
mat2495 Posted June 29, 2021 Share Posted June 29, 2021 (edited) Thanks for the update Maverik, I've been having a few similar issues with mine, so I know what I will be checking this weekend! Edited June 29, 2021 by mat2495 Quote Link to comment Share on other sites More sharing options...
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