Aragorn Posted July 9, 2009 Share Posted July 9, 2009 Ok so you'll probably have seen my previous thread relating to runnign problems etc. The disco is now all running, although we havent driven it much and still need to sort the fuelling out a bit better and replace some ignition components. Anyway, its been driven a few times, relatively short journeys, first to the MOT and back, second from my mates place home, then a 10-15 mile trip round about moving some stuff around. Each time i've gone to use it, i've checked the water level, and each time its dropped in the expansion bottle. I'm not sure if the amount used is relative to how long its been run, as i didnt really measure how much i topped it up by the first few times, but the last time i put about half a litre in, after having driven it maybe 5-10 miles. At first i thaught it might have just been working some airlocks out, but i think its perhaps leaking from somewhere... My problem is i cant work out where... Theres no signs of wetness anywhere on any pipes in the engine. Theres nothing coming out the exhaust obviously at least (ie no clouds of white reek), and the oil level is exactly where i left it. Any ideas where i should be looking to track down the leak? Or any tips/tricks/ideas to help locate it? Also, how long should i leave it before its safe to open the cap to check the level? Common sense says that if the water is at a thermostatically regulated 88c then it should be ok to open the cap as it wont boil once the pressure is released, however i want to be sure before i attempt to melt my face off. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted July 9, 2009 Share Posted July 9, 2009 Valley gasket leaks are difficult to spot as the liquid boils off. Are you sure you are loosing coolant externally and not internally? Quote Link to comment Share on other sites More sharing options...
Rich_P Posted July 9, 2009 Share Posted July 9, 2009 With the engine up to temperature the water will splosh out at you when you undo the cap, because it is under pressure. Try running the engine up to temperature, with the header tank cap off and see what happens. You might be able to see it "drinking" the coolant, or you might have the beginnings of a head gasket failure and the pressure is not exceeding the cap's rating yet. Just so you know, it took us several weeks to confirm that a head gasket had gone on a Mercedes. It had incredibly mild head gasket failure symptoms, that gradually worsened over the following weeks. Eventually it began to leak water out of the header tank's overflow pipe, until we found the cap was past its best. Replaced the cap and it stopped leaking out the overflow. However just a week later the rate of water consumption increased. If the engine was revved to 2,500rpm it would only then generate clouds of steam, at idle it was barely noticeable. So be weary of a head gasket in its early stages. Quote Link to comment Share on other sites More sharing options...
Quagmire Posted July 9, 2009 Share Posted July 9, 2009 Mine didnt leak when i first filled it- and then i added antifreeze! That found all the weak spots Now i seem to generally be fine, but still have to tighten the odd hose here or there, and they have been gradually getting better. I tend to check every month or so and just top up perhaps half a litre i reckon. Thats doing 70 miles a day during the week. My favourite spots for leaks are the rear of the inlet manifold where the heater pipe connects (hard to see under the air filter) and the rubber pipes connecting heater pipes to water pump.... That and the crappy silicon sleeve for the Kenlowe capillary in the top hose, soon to be replaced with an x-fan switch thing i think. Quote Link to comment Share on other sites More sharing options...
steve_d Posted July 9, 2009 Share Posted July 9, 2009 Silly question. You are only filling to the fill level in the header tank and not right up to the top? The air gap in the tank is to allow for expansion. Steve Quote Link to comment Share on other sites More sharing options...
paintman Posted July 9, 2009 Share Posted July 9, 2009 Get it pressure tested when cold. Done that to my RR - OK so I have a tool that I can use to pressurise the system. Surprising just where water leaks out! As said, when hot the escaping water boils off instantly so making leaks much harder to find. Any of the plugs unusually clean? Quote Link to comment Share on other sites More sharing options...
Aragorn Posted July 9, 2009 Author Share Posted July 9, 2009 How would i go about pressure testing it when cold? I'll go back over all the jubilee clips and ensure they're super tight. I'll also try running it with the cap off and see what happens, and i'll check the spark plugs to see if any of them look abnormal which would suggest the water is entering a cylinder. Any way to diagnose a valley gasket leak? I do hope its not a head gasket failure! I guess it might be worth sticking a compression tester on it too? It appears i have a knack for picking good "cheap projects" dont i! and ye, i'm only fitting it to the fill line! Cheers Quote Link to comment Share on other sites More sharing options...
Rich_P Posted July 9, 2009 Share Posted July 9, 2009 I do hope its not a head gasket failure! I guess it might be worth sticking a compression tester on it too? May or may not show a head gasket failure. The Mercedes in question had full compression even though it was consuming coolant from the gasket failure. Quote Link to comment Share on other sites More sharing options...
nas90 Posted July 10, 2009 Share Posted July 10, 2009 Is the engine a 3.5 or 3.9, how many miles on the clock? If 3.9 seriously suspect cracked block and water coming up the liner into one or more combustion chambers. Is the engine coolant temperature gauge getting towards the red I am about to explode end of the scale? You will not see a loss of water externally only the water level dropping in the expansion tank as it steam cleans a combustion chamber(s).............. If 3.5 could be head gasket or the valley gasket, liner problems not really applicable to the 3.5 because not bored like the 3.9/4.2/4.6 and the block strong enough not to crack. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted July 10, 2009 Share Posted July 10, 2009 How much are you putting in? If you are overfilling the expansion tank then it will spit some out and settle down to a level. How much remains in the tank when you top it up? Quote Link to comment Share on other sites More sharing options...
jwriyadh Posted July 11, 2009 Share Posted July 11, 2009 Cold pressure testing: Disconnect one of the heater pipes, block one of the openings. Now bodge a tubeless tyre valve into the other opening. Pressurise from a pump or compressor or spare tyre to about 18 psi. Rad cap should release pressure to 15 psi. Watch the system for water leaking and check system pressure with a tyre pressure gauge. Simples. jw Quote Link to comment Share on other sites More sharing options...
paintman Posted July 11, 2009 Share Posted July 11, 2009 Sorry for the late reply, but ^^^^^ its already been covered. I have a hand operated pump that enables me to pressurise or create a vacuum & the business end is just right to fit into one of the small hoses that goes to the header tank on mine. 20psi showed the culprit nicely. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted July 11, 2009 Share Posted July 11, 2009 Another quick test is to remove all the plugs one by one Check to see if one / any look as though they have been steamed cleaned, if so thats the culprit cylinder Nige Quote Link to comment Share on other sites More sharing options...
Aragorn Posted July 11, 2009 Author Share Posted July 11, 2009 I've been away to london so havent had a chance to check anything out, but thanks for the tips, i'll try and check things out next week once i'm back. I'll check the plugs, but i've only just changed them, and they were all similarly black when they came out, although the motor wasnt driven on the road with the old plugs, so the new ones might show something different, however as i say theres nothing from the tailpipe. It's a 3.5, and i've been filling it to the level shown inside the tank as "fill level". Quote Link to comment Share on other sites More sharing options...
Aragorn Posted July 12, 2009 Author Share Posted July 12, 2009 Well i decided to have a quick look at it tonight when i got back, it had used some water, but not as much as previous times, even though its last trip out has been its longest yet... Topped it up with the small amount it needed then fired it up with the cap off. Water in the tank looked fine, no bubbling or anything untoward. The level dropped slightly when i revved it, then came back up when i let off. Its late, so i didnt go into checking the sparks etc, i'll do that at some point this week, as well as keeping a close eye on the water level any time i take it out. If it can be done cheaply a water level sensor might be an idea i should look into. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted July 12, 2009 Share Posted July 12, 2009 good news is 3.5s don't suffer liner / block issues, if anything a head gasket, or poss an airlock, so don't break out the razor blades just yet Nige Quote Link to comment Share on other sites More sharing options...
nas90 Posted July 12, 2009 Share Posted July 12, 2009 What Nige said, lucky it's a 3.5, cost me £3K with Turner Eng for a 3.9 for the nas with cracked block and water up the liner Try all the cheap easy to check things first before starting to take things apart. Park over a nice big piece of clean cardboard on level ground with a hot engine you might just get an idea of where you are getting a leak. Check the radiator if it's the original probably time to get a replacement. With a 3.5 more usually a hot engine warping the heads because someone has let the engine boil because the rad is blocked........................ Guessing you have carbs not injection? Dave Quote Link to comment Share on other sites More sharing options...
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