| Author | Message | ||
     John Cronin (Jec) New Member Username: Jec Post Number: 34 Registered: 02-2003 |
Here's an update on my previous thread with some new diagnostic information, in the hopes that some of you may have some more ideas... 95 Discovery with 86,000 miles Left exhaust manifold cracked and replaced 15,000 miles ago Right manifold just cracked and replaced Downpipe flange welds cracked and repaired at 40,000, 55,000, and the right downpipe with the current manifold replacement at 86,000. Looked for the first time after this replacement and noticed that BOTH manifolds glow red (lower couple inches of manifold and top couple inches of downpipe) when pulled into garage after our daily drive home, which is a 17-mile climb from 4,000 feet to 8,500 foot elevation, maximum 8% grade. When I drive at 50 instead of 60, red area is only half as big. No check engine light Engine coolant temperature is normal No loss of performance No change in gas mileage About half the plugs look lean, the rest normal I just got two new O2 sensors from Nathan and put them in, and was hoping the best, but the manifolds are STILL GLOWING RED!!! (I think I did notice some improvement in performance, though). Timing is right on at 6 BTDC Fuel pressure is 34 psi Fuel filter changed 11,000 miles ago Manifold vacuum here at altitude is 12 in Hg at idle (and steady); at 4,000 feet it is 14 at idle and 18 at 2,500 rpm. No loss of vacuum from this 18 at 2,500 rpm, which, according to the link Todd posted, suggests that the exhaust system is not clogged. Haven't run Techron yet, waiting to get the tank down near empty. Will probably change the fuel filter for grins, but if it was clogged, we wouldn't be able to drive up the hill as strongly as we do. Dealer mechanic tells me that they have seen (at 5,000-feet at their shop) red manifolds on Discos without any known problem; he thinks it's normal and we just need to take it easy up the hill. So before I give up and resign myself to continuing manifold replacement, does anyone have any other thoughts? Thanks again for the help to date, and sorry for the long post. John | ||
| J E Robison Service Co (Robisonservice) Member Username: Robisonservice Post Number: 68 Registered: 10-2002 |
I'd suggest you take it to someone who has the proper test hookup to view the engine parameters when the truck is driving under conditions that get the manifolds red hot. That should show what the computer is thinking when the problem occurs. Red hot manifolds are not normal, and will assure future troubles like burnt valves. You will probably have to find an independnet with an Autologic or Rovacomm system for this. Your truck is not OBD II compatible. John www.robisonservice.com | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 256 Registered: 04-2001 |
Did you pull one O2 plug and run it with a check engine light and see what happens or did you just replace the sensors? The reason I suggested that was a CEL makes the truck run rich. If it still had glowing manifolds with the CEL on then you know you have another issue. It is a crutch for proper diagnosis but it will lead you in the right direction. If nothing else you could rechip the ecu, change the timing, or something on that order to compensate for the lean condition. Ron | ||
| John Cronin (Jec) New Member Username: Jec Post Number: 35 Registered: 02-2003 |
Ron: the new sensors showed up before I had a chance to pull the plug, so I put them in. I'll try pulling the plug on one tomorrow. John: 200 miles to the nearest shop - that's why I'm trying to rule out as much as I can before resorting to that. Plus the fact that they were not very optimistic that they were going to be able to duplicate the problem if we took the truck there, due to the possible involvement of either the altitude or the nature of the drive up the hill. Thanks both, John | ||
| John Cronin (Jec) New Member Username: Jec Post Number: 37 Registered: 02-2003 |
More data: Drove 10 miles on flat highway at 4,000 foot elevation tonight,cool air (50 degrees)at 70 mph, and that was enough to get the same amount of glowing as described above. Then climbed a mild hill to 5,500 feet at 50 to 55 mph, and that was enough to get the entire left manifold red (more noticeable in the dark). Something is definitely wrong here, and I no longer accept the dealer's comment of "normal". | ||
| Roland Kutasi (Disco1) Member Username: Disco1 Post Number: 55 Registered: 10-2002 |
Hi John! Here's a thought that's out of left field. Check your radiator as it could have a hot spot, that is, despite the fact that your temperature gauge is showing normal (due to the efficiency of the fan) you could still have a blocked radiator, this could explain why there is no engine check light, and other diagnostic attempts are showing a negative result. Lets know how you get on. | ||
| Bill Bettridge (Billb) Senior Member Username: Billb Post Number: 740 Registered: 02-2002 |
This has nothing to do with coolant temp - it is lean due to timing or fuel delivery. Did you try retarding the timing at all yet - just as an experiment? Check fuel rail for rust/blockage - pull injectors and check for blockage - you can have them sent out and rebuilt for not alot. Any access to another computer top swap in and drive? I realize that's kind of a shotgun approach, but since you're so far from anyone with test equipment - anything is worth a shot. Like you said - even if you took it to a dealer that thinks this may be normal (?!) - no guarantee there either. Bill | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 261 Registered: 04-2001 |
Bill is spot on, if it does not clear up with the CEL it points to a fuel, timing, something in the motor. If it clears up with the CEL it points to a sensor issue. Ron | ||
| John Cronin (Jec) New Member Username: Jec Post Number: 39 Registered: 02-2003 |
Thanks, guys. Will get at the checking as soon as it stops snowing. Roland - what's the recommended procedure for the radiator? Shut off the engine, remove the shroud, and feel around on the fins with my hand? John | ||
| Roland Kutasi (Disco1) Member Username: Disco1 Post Number: 64 Registered: 10-2002 |
There seems to be two possible causes. You are running too lean or too hot. With the mileage you have it's possible that your radiator has corrosion inside the cores this would cause the hot spot/blockage. The only way you can be sure is to take the radiator out and have it pulled apart. It seems that you will need to take the vehicle to a dedicated service center (preferably not a dealer)and run both senarios past them. | ||
| John Cronin (Jec) New Member Username: Jec Post Number: 40 Registered: 02-2003 |
Ron: With the engine at operating temp, but not overly hot, I pulled the connector for the left 02 sensor, and then proceeded to drive 5 miles back uphill to home. The CEL did not come on instantly like I expected - it did not come on until I was home and had idled for a while. I noticed no significant change in performance driving up the 8% grade at 50 to 55 mph in 2nd (which we normally do). And both manifolds were still glowing red. When the CEL finally came on, I had a 44, matching my having pulled the left connector. Do you think the delay in the CEL coming on has any significance? Do you think I've ruled out a cat problem? If so, then I'll try Bill's retarding idea. The injectors are sounding suspicious, particularly in light of the rust possibility, but having looked at the removal procedure in the manual, I'm not looking forward to the operation, so am looking for easier possibilities first. Any other comments? Roland: This is a single-owner truck, and we've changed the coolant regularly, so I would hope that the cooling system is still functioning properly. Why wouldn't the temp sensor reflect elevated temps if the radiator was blocked? Thanks, John | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 264 Registered: 04-2001 |
The delay in the CEL is not suprising that is the way it works with the early trucks (on GEMS the computer see a heater circuit fault and the light comes on right away). The change in running will only occur once the CEL is on, so if you have not driven up the hill with the CEL (I cannot tell from your post whether this is the case or not) you cannot tell if it has an effect on the manifolds glowing. Ron | ||
| John Cronin (Jec) Member Username: Jec Post Number: 41 Registered: 02-2003 |
Ron: No, the first test was not with the CEL on, so I repeated it. Disconnected left sensor here at home, drove 13 miles down the hill with no CEL coming on, turned around, started back up the hill, still no CEL coming on. Halfway up the hill I pulled over and let the engine idle. Checked the manifolds. The right was glowing fully, the left only a little bit. When I got back in the truck, the CEL was on. Drove the rest of the way up the hill - still no significant loss of performance. Once I got home, both manifolds were glowing fully, though the left was slightly less red than the right. So what do you think? Thanks, John P.S. the only bright spot (other than the manifolds) was that the full moon on the snow-covered Sierra was really nice | ||
| John Henley (Johnhenley) Member Username: Johnhenley Post Number: 41 Registered: 12-2002 |
Clogged Cat. Period. | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 265 Registered: 04-2001 |
Well that pretty much rules out it being an MAF or O2 sensor. You are down to something major in the system. If it is a clogged cat like John says you would have a rattle (most likely) and definately a change in performance. Did you do a fuel pressure test at the shrader valve? Ron | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 266 Registered: 04-2001 |
Nevermind I saw 34psi above. If it were me I would just retard the timing to compensate. Ron | ||
| John Henley (Johnhenley) Member Username: Johnhenley Post Number: 42 Registered: 12-2002 |
"You are down to something major in the system. If it is a clogged cat like John says you would have a rattle (most likely) and definately a change in performance." Not nescessarily. We used to see this quite a lot on big block fords. The o2 sensors go to shit then call for lean, then it melts the internals on the cat, causing it to loop as "rich" calling for LESS fuel, therefore increasing temp. Real common actually to NOT have a rattle. You should be able to read the codes, then also check the sensor for range out of the vehicle. You can also do a flow test on the cat. Too bad its not obdIV.............. j | ||
| John Henley (Johnhenley) Member Username: Johnhenley Post Number: 43 Registered: 12-2002 |
"You are down to something major in the system. If it is a clogged cat like John says you would have a rattle (most likely) and definately a change in performance." Not nescessarily. We used to see this quite a lot on big block fords. The o2 sensors go to shit then call for lean, then it melts the internals on the cat, causing it to loop as "rich" calling for LESS fuel, therefore increasing temp. Real common actually to NOT have a rattle. You should be able to read the codes, then also check the sensor for range out of the vehicle. You can also do a flow test on the cat. Too bad its not obdIV.............. j | ||
| John Cronin (Jec) Member Username: Jec Post Number: 42 Registered: 02-2003 |
Well guys, I decided it was time to break down and take it to a local mechanic and see what they think, so the Red Rover (which name now has double meaning with the manifolds) has a date at Mr. K's Monday morning. They said they could check back pressure on the cats, and will take it from there. I'll post the verdict once it's in. John, no codes showing on the OBDI reader under the seat, and I don't think the shop here will be able to pull anything else, so we'll just have to see how good their diagnostic skills are. Ron, I'll keep the retarding in my hip pocket in case they can't find anything else. Also talked with them about pulling the fuel rail and injectors to check them if they can't come up with anything else - they gave me a quote that was far less than the aggravation it would cause me, so hopefully they'll be able to get to the bottom of it. Thanks again for everyone's input. John | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 267 Registered: 04-2001 |
John H., that certainly could be the case on Fords but it is something I have not personally seen on rovers which is why I said it was unlikely. John C., good move, I think we have reached the end of what can be done over the internet. Ron | ||
| todd slater (Toddslater) Senior Member Username: Toddslater Post Number: 273 Registered: 08-2002 |
Wow, Been outta touch this week and am just getting caught up. I definitely agee with Ron regarding reaching the limits of internet diagnostics. Also, I have experienced the no rattle clogged cat that John has with Fords. It'll will be interesting to see what the back pressure on the cats turns out to be. | ||
| Jeffrey L. Price (Jlprice) New Member Username: Jlprice Post Number: 6 Registered: 02-2003 |
Not sure what problem you have there, but red hot exhaust manifold is normal. A useful link attached. http://www.aera.org/Techside/exhaust%20gas%20temp.htm Exhaust temp under load should be in the 1100 to 1400 F range. If you want to corroborate, look up the temperature of combustion for Octane in a thermodynamics text. Red range of cast iron runs from 750 to 1800F. Link attached http://www.zianet.com/ebear/metal/heattreat4.html. Not many people are competent to weld cast iron, so I would be hesitant to trust failure of a repaired maifold as indication of anything other than a bad weld. It will be interesting to see what the actual problem turns out to be. cheers -jeff | ||
| John Cronin (Jec) Member Username: Jec Post Number: 47 Registered: 02-2003 |
Jeff: Wow! It would be really interesting to hear from another 95 disco owner if their manifolds glow when checked at night (when it's easy to see) immediately after a 10 mile highway speed run. I'll be sure to post the shop's diagnosis. Meanwhile, it was NEW manifolds that I put in - the repair was the weld that holds the flange onto the downpipe. Thanks, John | ||
| Jeffrey L. Price (Jlprice) New Member Username: Jlprice Post Number: 8 Registered: 02-2003 |
I have run a gas engine on a dyno stand. It has been a while, but my recollection is the manifolds glow pretty quickly, after about 10 minutes at or near full throttle. They were typically cherry red after 20 minutes. I would figure that a ten minute hill climb would make them visible. How fast they glow is a function of how massive the exhaust manifold is and how hard the engine is working (which effects the exhaust gas temp). I think that not many people can repair that Y-Pipe properly and an improperly executed repair could damage the cats, or alter the gas flow in the pipe, or result in mis-aligned flanges which would introduce stress on the manifold and the pipe causing one or both to fail prematurely. The fact fact that it has been repaired several times is consistant with this. Did some singular event occur that caused the original failure? I am thinking that something caused the failure of that Y-Pipe flange which was improperly welded, and the subsequent work has just been patching up that original bodge. I am not certain you will be able to find a root cause at this point, but it will be interesting to see what is required to make that exhaust flange seal. My guess is, replace the Y-Pipe and your problems go away. -jeff | ||
| thom mathie (Muskyman) Senior Member Username: Muskyman Post Number: 252 Registered: 11-2002 |
i think you guys are all a little freaked my 94 has glowing manifolds after pulling a big trailer at highway speeds. I have seen it a number of times over the last 50k and it still runs perfect so whens it going to cause me a major failure? yes a plugged cat can make them really glow bright, some BMW's with aged cats glow like a hot horse shoe at a blacksmith shop. look at the conditions this truck is seeing constant load while climbing to altitude...unless its spitting codes and spark plugs look terrible lean I say its not a big deal.you can sometimes baffle everyone looking for such a condition when in reality it could just be that those particular exhaust manifolds have more casting flash inside them causing more heat to be retained in the manifolds. there is no doubt well documented evidence that they all run very hot...just look at how many cracked manifolds there are out there. what are the plugs looking like? what other symptoms does it show? | ||
| John Cronin (Jec) Member Username: Jec Post Number: 48 Registered: 02-2003 |
Jeff: Original failure was found when dealer pulled engine at 40k miles to replace stuck exhaust valves. They welded the flanges, said "it happens all the time. We had not bottomed out on the exhaust system or anything like that to my recollection. Thom: Thanks for the first report of other red disco manifolds. About half the plugs looked pretty lean, but no other symptoms than cracking manifolds and downpipes. As of lunch time, the shop said cats were not clogged, and the mixture looked fine, but they're doing more diagnostics. I'll keep you posted. Thanks, John | ||
| Blue (Blue) New Member Username: Blue Post Number: 36 Registered: 04-2003 |
hey Musky, is that why it hurts so much when I brush my forearm against the manifold while reaching for those damn bolts? | ||
| John Cronin (Jec) Member Username: Jec Post Number: 50 Registered: 02-2003 |
Final update: Shop could pull no other revalent diagnostic info. But cats and muffler are definitely generating no undue backpressure, even at redline, and mixture looks great. Well, now that I've replaced both right and left manifolds, they'll be easy to do as scheduled maintenance (LOL). By the way, checked compression this weekend and it looked great, so no sign of burned valves yet. I may try retarding the timing a bit to see if it helps the glow without degrading performance too much. Thanks again to everyone for all the help. John |
