Looking for a holistic approach to treating an engine prone to failure...

Hi all,

I am going to attack this from a different direction. I have an '86 Cherokee Diesel (2.1L Reanult 4cyl.). These engines are pretty ridiculous. They act like handgrenades. They do okay around town at low speeds, but stay at highway speeds for more than half an hour or so and kaboom. I know it's not just my engine. This is a common problem with these engines. In fact, as I have gone through spare engines in my attempt to salvage mine, what made the search so difficult was that they all had blown head gaskets. I am on the fourth headgasket in the life of my engine (second one during my ownership). I am currently having the engine rebuilt from the best parts of three engines.

Now, one day I would like to do an engine swap and put in a 4BT or MB from a 300TD or one those beauties from OBWCanada, but right now I don't have the time or money for that. I'm currently trying to come up with ways to safeguard the future of my fragile Renault engine. I am going to upgrade the cooling system and welcome any advice on that (I'm currently considering a kit from Flex-A-Lite). But here is the big question for this post:

What do you do when something is prone to failure? What makes these head gaskets so prone to failure? Is it just an issue of heat? The symptoms certianly point to an overheating issue (blown head gaskets, cracked blocks, cracked heads). Is that all there is to it? Are there other factors at play like materials used in the original design? I'm trying to take a holistic approach to this and address the root of the problem and not just the symptoms. Is there anything I can do to improve upon the original design, to make my engine less prone to blowing up in my face while going the speed limit on a level highway?

I welcome any comments or feedback. I know, in the end, this engine might be a lost cause, but it is all I have right now. The next time it fails will be the last, as I can't afford to keep it going after this round of surgery. That will be a sad thing, indeed. The vehicle is in great shape and has so much life left in her. Please help. It's not over til it's over and I'm going to fight for her to the last.

Thanks.

I'm guessing as a start that the design itself is prone to failure owing to poor control of thermal expansion in the head. It seems to be characteristic of some aluminum head designs, and aluminum head diesels in particular. Anyone who's dealt with Rabbit or Peugeot diesels (or Peugeot gassers) will know what I'm talking about. As to a cure, I don't know, but I would guess that cool running would be a good place to begin. As I recall from my old Peugeot days, it was also considered a good idea to retorque the head periodically even when there was nothing wrong. In addition, head warping was a big problem with the Peugeots, and it was imperative after a head gasket failure to have it carefully checked, and milled if necessary. Even a tiny bit of warp would lead to repeated failures.

Rabbit and Jetta diesels were pretty notorious for blowing head gaskets too, but seem not to have had such warping problems.

Have you consulted with any real diesel experts out there, to see if there's a magic gasket treatment or something that would help?

I would map the coolant passages and take note of where the failures occur. Perhaps some cross-flow holes may be in order to promote an even block temp.

If the failures do not occur in the same region of the block and corresponding regions of the head, I would have to say that the materials and design are inadequate. It is then a lost cause and youshould start looking for that 4BT.

How many bolts hold the cylinder head down? If there are only 10 on your 4-banger, there may be insufficient clamping force; this can cause a head gasket to blow in a high-compression engine (such as a diesel) - So, the short answer, what goodburbon said. "You can't polish a turd."

C-4 will put it out of its misery, anything designed in france and junk have a lot in common. Sorry, not much hope there.

A few things come to mind:

head bolts.... use new high quality bolts each time and check the torque/retorque monthly.

Heat. It is probably not so much an issue of the radiator not tranferring the heat to the air as it is a matter of transferring the heat from the engine to the coolant. Since your problems come at highway speeds it is not a fan issue, the foward movement of the vehicle moves more than enough air through.

Look at high quality coolants and SCA's. A trip to your local CAT dealer will get you some expensive, but very high quality coolants. And even better way to go is Evans NPG coolant found here:

http://www.evanscooling.com/catalog/C_npg1.htm

Expensive yes, but worth every penny IMHO.

Next time you replace a head gasket place it against the head and block and see if there are holes in the gasket where there are none in the block or head, or vice versa. Quite often gaskets will be made for multiple configurations and the manufacturers don't drill all the possible coolant passages...you can drill them yourself to match the holes in the gasket (do it on a blown head/block first to make sure it goes to coolant passages). Or there may be coolant passages but the gasket blocks them, even an easier fix.

Try the Evans NPG coolant first, I have a feeling it may help a good deal.

That engine is very popular and scuessful in europe. it also was used alot on the winnie lasharos.. why not rebuild it with top quality new parts instead of junk old parts between europe, and the lashero suppliers and even NAPA you can get enough new parts to do a true and quality rebuild of the engine

Thanks guys. Some good thoughts so far. I will definitely look into that Evans coolant. Thanks for the link.

So, are you saying that you think a radiator upgrade is a waste of time and money? An inexpensive route (instead of the Flex-A-Lite) would be to get an OEM radiator from an '86 XJ with an automatic transmission (mine is a manual). My understanding is that the automatics have larger radiators. It would be a factory fit and offer slightly better cooling. Would this be a worthwhile upgrade? At the very least, I think I will have to get a new thermostat. The temp guage was reading fine the last time I overheated so it was clearly not doing its job. Basically, I had no warning except for the smoke that all of a sudden appeared immediately following the blown head gasket (and melted/fused piston).

A period retorque is something I will definitely do in the future. Thanks for that advice, too.

And the rest of you are right, too. This engine might not be worth it to save. It was a piece of junk to begin with, apparently, and will forever be a piece of junk. Still, if I can just keep it going for a little while longer I can justify and afford to do the engine swap I'm wanting to do. If I have to scrap the whole thing, there's little chance of me ever building a diesel XJ, as the regulations here in CA make it impossible to repower a gas car to diesel and I doubt I will come across another diesel XJ (which is smog exempt and can be repowered without any titling issues), especially one in as good a condition as mine.

Anyway, thanks for your continued help and guidance in this.

wilcharl said:

That engine is very popular and scuessful in europe. it also was used alot on the winnie lasharos.. why not rebuild it with top quality new parts instead of junk old parts between europe, and the lashero suppliers and even NAPA you can get enough new parts to do a true and quality rebuild of the engine

Click to expand...

I know of a place where I can get a low-mileage newer engine from a place that deals in LeSharo parts and such, and have thought about that, but as this problem seems to be more of an epidemic across all the engines I have come across, regardless of age and/or mileage, I am a little reluctant to invest that much in another 2.1L Renault 4 cyl. I figure I might as well hold on to that money and save up for a nice 4BT or SD33 or 2.8NGV or Mercedes or whatever. Even the LeSharo owners I have spoken with, which used a detuned version of the engine (less HP but more torque), have had the same problems I am having.

Who was it here that did a MB conversion on an MJ a few months ago ?