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Rebuilding a 4.0. Couple of questions regarding passing water into exhaust.
Hey guys,
A little back story, I purchased a 1997 P38 SE for pretty cheap. I knew it needed work and have the means to do so, and also wanted a project truck. Having come off of a fresh 2000 P38 resto I got a really good vibe from these trucks, and love the lines. So I figured why not, knowing the risks with these engines I went for it anyways. The '97 had a small oil leak out of the crank seal but otherwise ran strong, with a solid driveline.
Fast forward a bit, I tore the timing cover off, water pump off, cam and crank gears, timing chain, and oil pan. I checked the bearings on the crank, no play. Water pump good, chain had a good amount of play. So I got all new gaskets for the mentioned parts, new gears and chain. Put it all together and it started up without a hitch.
When I drained the oil there was no sign of a blown gasket and good compression. I put the radiator back in, fill it up with fluids, idles great. Go for a quick spin down the block and it starts to over heat. I bleed the cooling system ensuring there is no air blocking flow. The radiator flows well, no cool spots. But it still overheats. After bleeding the system I go for another ride, this time up some hills to test the cooling. I was able to drive about 10 minutes before it moved past 12-O-Clock on the temp gauge.
Take it back home, no water in the header tank, fill it back up and let it idle checking the exhaust, lots of vapor passing through.
So today I pull the heads off, gaskets look golden (for their age). No visible cracks in the heads or between the valves. I check the liners and there is no scoring or visible damage.
This week the heads will be getting put on a bench and pressure tested as well as refurbished (new seats etc).
When I was removing the heads the bolts were extremely tight, I know they call for a 3 stage torque, 15lbs then 90deg and 90 deg according to ALLDATA. This felt more like 80-100lbs. But I figure if it was that much the soft aluminum threads would have been pulled. But I know the material between the head bolt and the water jacket is extremely slim and I fear that even though there is no liner damage that there could be a crack in that area.
Anyways, I have read all about this engine in the past week regarding the issues and weaknesses. My question is, does anyone have any advice about where the water is passing into the cylinder from? I can see rust on the exhaust valve heads. I do not feel comfortable putting it back together without really knowing what the issue is, pending the head testing.
Sorry for the long winded post, it was for the sake of completeness. Let me know what you more experienced Land Rover owners/builders have to say. Thanks.
Since you mentioned ALLDATA, you might also want to download a free copy of the factory manuals, called the RAVE, link below.
In some cases a single overheating event can cause a liner to slip. Hopefully no "ticking". Slipped liners are not the original cause of oveheat, but they can be the end result.
Machine shop will check for head flatness, may have been warped head doing the leaking. Get new head bolts of course (stretch). Previous owner may have re-torqued for problem leak.
Thermostat jammed with trash from all the work? Not saying you can't eat off the floor in your shop, but sometimes it only takes something small. As cheap as they are, new stat of your choice. I suspect that a 180 is a good choice for an alternate, 160 is too low.
Pix of my 4.0 liter D1 temp guage and scanner at 207F. Temp is monitored by ECM on a two wire sensor, near themostat. Temp guage runs from adjacent single wire sensor. 12:00? Wow!
Since you mentioned ALLDATA, you might also want to download a free copy of the factory manuals, called the RAVE, link below.
In some cases a single overheating event can cause a liner to slip. Hopefully no "ticking". Slipped liners are not the original cause of oveheat, but they can be the end result.
Machine shop will check for head flatness, may have been warped head doing the leaking. Get new head bolts of course (stretch). Previous owner may have re-torqued for problem leak.
Thermostat jammed with trash from all the work? Not saying you can't eat off the floor in your shop, but sometimes it only takes something small. As cheap as they are, new stat of your choice. I suspect that a 180 is a good choice for an alternate, 160 is too low.
Pix of my 4.0 liter D1 temp guage and scanner at 207F. Temp is monitored by ECM on a two wire sensor, near themostat. Temp guage runs from adjacent single wire sensor. 12:00? Wow!
Haha, on the P38 (mine anyways) the temp gauge is horizontal. Thanks for all the info. Is there anyway to visibly see a slipped liner? They all seem to be flush. I will definitely check out a 180 stat for sure. I tried out two thermostats that I had available. One I know was working the last time it was on a vehicle but it has been a while since it has seen action. Will for sure get a new set of bolts with the gaskets.
If you took fan and clutch off as a unit, should be good, UNLESS PO had that problem. Reversed fan can do wierd things at roadway speed and slow speed. My PO, who employed an advanced village idiot mechanic, replaced condenser fans and wired them backwards. Overheat at idle like hair on fire.
Would think if it is a reversed fan, it would idle sorta OK (air would just blow out the front). AC would be poor, high head pressure from too much temp on condenser. At some speed on the roadway, air in = fan wrong way = no cool radiator. But that would probably be about 15mph, not 60 (try holding a pizza box out the window).
Have seen posts on other sites about the liners, and "pinning" them so they can't slip, for about $100.
Bad thing about Rover gauges is that they are designed to reduce service complaints - they stay in the same place. Mine reads the same from 145 on the scanner to 239, where I chickened out...
My bad - missed year on route. But you had it, which is good. I think it should be printed out like a label and put on fan cowl with clear shipping tape.
If you took fan and clutch off as a unit, should be good, UNLESS PO had that problem. Reversed fan can do wierd things at roadway speed and slow speed. My PO, who employed an advanced village idiot mechanic, replaced condenser fans and wired them backwards. Overheat at idle like hair on fire.
Would think if it is a reversed fan, it would idle sorta OK (air would just blow out the front). AC would be poor, high head pressure from too much temp on condenser. At some speed on the roadway, air in = fan wrong way = no cool radiator. But that would probably be about 15mph, not 60 (try holding a pizza box out the window).
Have seen posts on other sites about the liners, and "pinning" them so they can't slip, for about $100.
Bad thing about Rover gauges is that they are designed to reduce service complaints - they stay in the same place. Mine reads the same from 145 on the scanner to 239, where I chickened out...
Thats not good! I planned on installing an oil pressure gauge, might do a water temp one as well. What scanner is that, do you have it mounted in your truck or is it a hand held like the Hawkeye?
just a hand held, so can use on other vehicles. Thinking about one that could dump to my lap top. Some people have added Glowshift oil PSI gauges (adapter goes on oil filter bottom - you also keep idiot light), volt meter, and temp.
On Discos, the tach serves as a defacto voltmeter, when alternator fries, tach quits. ANd we just have the oil idiot light, which turns on below 7 PSI - want to drive around town with 9 PSI of oil ?
what cylinder had the rusty valves??
If it was one of the middle cylinders then a good chance the block is cracked behind the liner and once things heat up the coolant goes behind the liner then gets into the combustion chamber, there was an outfit that made clear plexiglass covers to simulate the heads and thus was able to pressurize the coolant system and find the leaking cylinder they did extensive testing to figure this out seems that #6 is the likely culprit
Mrmerlin, to me it looks like ALL the cylinders had rust on the valves. See the attached pic. The white valves are what I would interpret as burnt coolant, maybe not rust yet, mostly on the exhaust valves. But I could be wrong, I am new to this 4.0.
When I checked the cylinders for water before I removed the heads it only blew out of #7 and #8.
Rebuilding a 4.0. Couple of questions regarding passing water into exhaust.
