QuestionHi John,
I am back with my 1996 Disco - still overheating. I will tell you what I have done to date and let you tell me I should have pressure tested the heads, which I will probably have to do still.
I had a shop do a combustion gas test on my vehicle, they said they stuck a tail pipe emissions probe into the overflow tank and ran the engine for an hour. They said they detected over 100ppm, which is enough that they called it a combustion leak into the cooling system. I don't know how the tail pipe emissions probe works when in a tank with possible antifreeze contact so I took them at their word that I may have a head gasket leak. So I tore down my top end and replaced my head gaskets (took me a day to clean everything properly). I examined everything closely as I took it apart looking for some obvious marker that I was leeking exhaust into the coolant system, but no indicator. All the piston heads were carboned so no coolant back into the cylinders and I have had no misfire codes so that also indicates no coolant in the cylinder. I finished the top end and started her up. She ran great, but after a while of driving it began to overheat, again.
The local landy dealer service guy turned me on to a landy mechanic that used to work there. He came over and looked at it and I told him everything I knew. He checked the flow of the radiator and said he didn't like it so I took the rad out and had it tested. Sure enough it was blocked up to 90% with some wierd white stuff the rad tester said was absolutely not calcium deposits!! So I got a used rad and had it tested, it checked out and I stuck it in. I drove that thing at least 45 minutes before it started to overheat (got up to about 230 degrees as the infrared thermo said when I stopped).
Of course I am kicking myself now for not having the heads pressure tested when I had them off, but I checked them with a straight edge and thought they were good. I never would have thought to have them pressure tested. But that is not the question I have for you. I have recently learned about "slip a sleeve" where the molly steel sleeve in an aluminum block will slip or move when the temperature gets to high for too long. Now I heard that this was a problem with the Disco II, not the Disco I. The landy mech thats helping me has asked me to take off the oil pan so that we can look up at the sleeves (I looked at them once the pan was off and they all looked the same. I did notice some black marks on the lower portions of some of the sleeves where the pistons ride.)
Here are some things I have been checking. I ran the engine until it said it was to temperature (dash gauge sensor not ECM monitor temp sensor, I don't have real time monitoring) and I checked the temp at the thermostat bell housing with a touch less therm probe by FLUKE, it read ~100. I then drove it for a while longer and checked again it said ~200. I then drove it for quit a while longer until it started getting hot and I stopped and checked it read ~230.
So my questions for you are as follows:
1. Could that junk that clogged my radiator be clogging my coolant channels and causing overheating. I have good flow through the rad now that I replaced it.
2. How hot would the engine have to get to "slip a sleeve" and is there any way I can check that. I know we are looking from the oil pan side, but I am afraid we would need to look from the head side. Which would give me an excuse to check the heads, while I have them off for the second time!!
3. Shouldn't a "slipped sleeve" give some kind of indicator on the head gasket that it is pushing HOT combustion gases into the coolant system. I found no markers when I pulled the heads off and believe me I spent at least an hour looking those gaskets over near the coolant paths.
4. Have you ever heard of a head fracture that would cause exhaust gases to get into the cooling system, but not show up on the head gasket.
5. What is the proper way to do a pressure test for a head gasket leak and a "slip a sleeve" leak. What should I be watching for on each?
I know I have said alot and asked alot, but I really need some expert advice. I am truly at my wits end and my wife is threating to put me in the landy and push us both over a cliff.
-Too Hot Disco in Alaska
Answer**************** Follow up ****************
Charles,
I wrote to a LR mechanic and passed on your questions. His response was this:
"I've got one (Disco II) in the shop right now that dropped a number 6 sleeve and you can hardly tell except for how clean the piston top was compared to the others. This about the fourth one I've seen in two years that has dropped a number 6 sleeve. As far as flushing we use a good two part flush I can't recall the name but you want the first part to be caustic when you read the ingrediants (sic). As far as how hot (sleeve drop question) it really varies vehicle to vehicle. But like I said the sleeve that dropped on the one I'm working on now you can barely tell a difference. According to Rover if you can catch your fingernail ont the sleeve its dropped too much (from below).
I hope this helps you avoid those cliffs your wife has in mind.
Regards,
JohnMc
NB: Autozone sells a product that can test for cracked head, headgasket or sleeve failure that could lead to coolant in the combustion.
If I find more info, I'll post another followup.
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Hi Charles,
I'm still looking into the 5 questions for you...I'll have more precise answers soon. First question is a "yes" but I and looking for something that other LR owners have used to flush these deposits from your engine.
I'll get back to you as soon as I have more data.
Regards,
JohnMc
