overheating help

zrtwooo · **Posted:** Sun Jan 04, 2009 9:35 pm

i have a problem when i have a high speed load like towing a trailer or climbing the hills from Phx to Prescott on I17. it just all of a sudden gets real hot at 65ish and only slowing to 55ish cools it down. i have a cel and was diagnosed as a egr. Its going in on tues am to get replaced... anyone know anything about this? is it the egr or something else?
thx
Mike

JL Rockies · **Posted:** Sun Jan 04, 2009 10:34 pm

I am no expert, but I have been suffering with something very similar. My KJ would get hot only on the highway as soon as I slowed down, it would cool off. I had no CEL and the stealer was stumped and could find nothing wrong with the the cooling system.
I thought it might be the tranny cooler heat soaking other stuff because it was far worse with the AC on. I an unrelated issue I had just put a can of Sea Foam in the tank.
I took the jeep out on the highway with the OD off (3.5K RPM) and the temp gauge hovered at 3/4 instead of rocketing fir the red zone. After a 10 min drive I turned the OD back on expecting the temp to shoot up; it did not. As I continued down the road the temp slowly went down to 1/2.

Here's my therory; my soot trap was clogged and the egr was increasing combustion temps to burn it up. I think that my blast down the road with the OD off cremated whatever was there and the egr chillaxed. I think the sea foam knocked some crap loose too.
I had this problem for weeks but know all is well

gmctd · **Posted:** Mon Jan 05, 2009 12:16 am

Plugged soot trap will increase EGT's with resultant high ECT's

KeighJeigh · **Posted:** Mon Jan 05, 2009 12:18 am

After a great deal of diagnostic work including replacing the EGR and the thermostat and back flushing the radiator I finally found the culprit in my 05: A defective fan clutch. This was the last thing I suspected because it looked fine and was spinning. However, when I had it running side by side with my wife's 06, I could then see it was running slower. In this case I wouldn't think it would matter as much at highway speed however.
This is a problem numerous people have mentioned in this forum. I think some simply deal with it and slow down while others may have put in larger radiators.

- Chris

nursecosmo · **Posted:** Mon Jan 05, 2009 12:51 am

JL Rockies wrote:

I am no expert, but I have been suffering with something very similar. My KJ would get hot only on the highway as soon as I slowed down, it would cool off. I had no CEL and the stealer was stumped and could find nothing wrong with the the cooling system.
I thought it might be the tranny cooler heat soaking other stuff because it was far worse with the AC on. I an unrelated issue I had just put a can of Sea Foam in the tank.
I took the jeep out on the highway with the OD off (3.5K RPM) and the temp gauge hovered at 3/4 instead of rocketing fir the red zone. After a 10 min drive I turned the OD back on expecting the temp to shoot up; it did not. As I continued down the road the temp slowly went down to 1/2.

Here's my therory; my soot trap was clogged and the egr was increasing combustion temps to burn it up. I think that my blast down the road with the OD off cremated whatever was there and the egr chillaxed. I think the sea foam knocked some crap loose too.
I had this problem for weeks but know all is well

If we had a soot trap (which we don't) that might be a possibility, except that EGR valves decrease EGTs.

It's probably just the fan clutch.

JL Rockies · **Posted:** Mon Jan 05, 2009 9:35 am

We don't have a soot trap??????? How is that possible????

Dealer checked EVERYTHING in the cooling system and came up with nothing. A jaunt down the highway at 3.5K cleared everything up. Besides, a bad fan clutch would make things worse in stop and go traffic not better as in mine and the thread starters case.

Must everything be so confrontational in this forum?

As I stated, I am no expert, but the experts so I had to figure it out myself by pouring through these forums. No I am reading to tow all of my stuff from FL to CO in 1 week from today!

zrtwooo · **Posted:** Mon Jan 05, 2009 10:06 am

If by soot trap you are refering to a "cat", It's empty with no change in results(except less turbo lag and quite a bit more pep). i don't understand how a faulty fan can cause overheating at highway speeds with a load but not in Phx summers in town. It cools down immediatly if i pull to the shoulder and keep it running. I dont want to start replacing things till it gets fixed. How does the EGR cool down the motor if it's introducing hot exhaust into the intake?
thx
Mike

JL Rockies · **Posted:** Mon Jan 05, 2009 10:29 am

That exactly the condition I had up until this past weekend. It gets pretty hot here in Ft Lauderdale too. Soot is a major problem for the EGR.

I am no expert and I may misrepresent what is actually going on. Maybe you're right; pay the $700 for EGR replacement; it's much easier than to try what solved the exact same problem I had.

zrtwooo · **Posted:** Mon Jan 05, 2009 10:38 am

ok so what is the 'soot trap" I need to get the egr replaced anyway.

PhoenixCRD · **Posted:** Mon Jan 05, 2009 11:35 am

zrtwooo wrote:

ok so what is the 'soot trap" I need to get the egr replaced anyway.

soot trap looks similar to catalytic converter (large cylinderical can on the exhaust before the muffler) there's some discussion as to what exactly the soot trap/cc realy is does.

what dealer are you going to? I and others have had good luck with Bill Luke.

I had a similar problem with my '05 and it was software related and repaired with a reflash of the CCN (instrument cluster control module). According to my paperwork it TSB 08-043-05. The EGR may just be coincident unless yours is an '06.

Paperwork reads
"symptom/condition: The customer may notice that the engine temperature gauge may indicate that the engine temperature is high. In hot ambient temperatures, and under certain driving conditiions of extended uphill driving while towing a trailer, the engine temperature indicator may indicate slightly above 3/4 normal operating temperatur mark on the temperature gauge (but below the engine hot temperature markings). Ths conditionmay be caused by an incorrect calibration of the engine temperature gauge."

My Liberty was doing this on the climb out of Black Canyon City with one person on board and in the cooler months, not towing.

Hope this helps

Gary

zrtwooo · **Posted:** Mon Jan 05, 2009 12:04 pm

THX GARY THAT DOES HELP AND THATS EXACTLY WHERE I FIRST NOTICED IT. MY WIFE, INFANT AND MYSELF CRUSING ALONG AND THEN I NOTICED IT...
THX
MIKE

nursecosmo · **Posted:** Mon Jan 05, 2009 12:13 pm

JL Rockies wrote:

We don't have a soot trap??????? How is that possible????

Dealer checked EVERYTHING in the cooling system and came up with nothing. A jaunt down the highway at 3.5K cleared everything up. Besides, a bad fan clutch would make things worse in stop and go traffic not better as in mine and the thread starters case.

Must everything be so confrontational in this forum?

As I stated, I am no expert, but the experts so I had to figure it out myself by pouring through these forums. No I am reading to tow all of my stuff from FL to CO in 1 week from today!

JL; you and I may be referring to two different things. In the automotive industry "soot trap" usually refers to a Diesel Particulate Filter or DPF, which we do not have on the CRD. We do have a catalytic converter, but that in no way traps soot, the holes are way too big to catch micron sized soot. Besides zrtwooo doesn't even have a cat.

A bad fan clutch certainly can give the symptoms described the above and in your own post. DI diesels run so efficiently at idle that they require very little air flow for adequate cooling what with the huge radiator and all. In this respect they are different from Gassers or IDI diesels which need a lot of cooling at low engine load. When the fan is really needed is under heavy load such as towing or a long climb. If the fan clutch is working properly you will hear it come on like a jet engine even at Hwy speeds as the radiator reaches the preset clutch activation temp. I have only heard my own fan come on a couple of times on long climbs up Jellico Mountain in Tennessee with a heavy load. Believe you me, when it comes on you WILL know it. Look up KeighJeigh's posts about his trials and tribulations with the above mentioned symptoms. I'm not saying that this is what you and zrtwooo have, but it is something to consider.

zrtwooo; How does an EGR cool the engine you ask? Remember that all of the heat generated by the engine is from fuel combustion. When the recycled gases are reintroduced into the combustion chamber they displace some of the O2 from the fresh charge air. Because there is insufficient O2 for an efficient burn, the combustion temperature is reduced, resulting in less NOx emissions as well as decreased mileage and power from the engine. Also those gases are not as hot as you may think after they go through the EGR cooler.

One other possibility is that there was a TSB for some of the 05's which corrected a software glitch in the computer which would give a falsely high reading on the dash temp gauge.

BTW JL. posting accurate, constructive information and correcting wrong assumptions is not confrontational, it is the whole point of this board.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

A few points worth considering and a suggestion for towing with an intermittent overheat condition:

1. If the low speed cooling is fine, not very likely to be a bad viscous fan clutch
2. High speed overheating, coolant flow is impeded or excessive heat load is building in the coolant system. Reasons could be coolant pressure isn't high enough, possibly by a bad radiator cap or the EGR valve is open too long, adding too much heat to the coolant via the EGR cooler. Out of those two possibilities, which one is known to be more problematic, the radiator cap or the EGR valve failing?

3. EGR when operating as intended, reduces peak in-cylinder burn temperatures, not coolant temps. It increases coolant temps because the ~1000*F exhaust stream is routed through an EGR cooler, cooled by your antifreeze mixture. It's relative - the peak cylinder temps are much higher than your coolant temp can ever reach.
4. EGR, if functioning properly, operates at idle (up to a couple of minutes) and very low load conditions, not while towing or at WOT.
5. Malfunctioning EGR, if stuck in even a slightly open position, may increase coolant temperatures dramatically under load for a couple of reasons:
a.) loss of boost out through the egr valve into the exhaust instead of the cylinders, reducing engine power, causing more fuel to be applied(via your right foot) than is normally necessary. More fuel = more engine heat load.
b.) excessive 1000*F exhaust flow through an EGR valve in the open position will flow through the EGR
cooler for far longer than intended, as in continuously. More speed = more exhaust heat transfered to your coolant in this case. This will add much heat to your coolant, by some estimates I've seen, as much as 40% more in a correctly functioning EGR system, with a malfunctioning one, much more than that.
6. The TSB used to install a software patch to the coolant gauge didn't fix anything related to increased cooling. For those of us who monitored the actual temps, we discovered that it changed the gauge calibration to be semi-logarithmic around the 12 o-clock position.

If you're going to be towing and don't have time to get the EGR valve replaced, put a block off plate on the egr feed tube where it enters the egr valve body. You'll get a MIL, but not a limp mode from this mod and it will eliminate any cooling issues caused by excessive heating of engine coolant by an open egr valve.

If you still have high speed cooling problems after blocking off the egr supply line, then you have either a coolant thermostat problem or other cooling issue. Either way, you can isolate it by blocking the EGR valve supply line. If the problem suddenly disappears, you've identified the cause. If not, you've eliminated the most likely suspect in order of probability.

This can be useful if your not comfortable with the dealer working on your CRD just before taking a long trip with a trailer attached. It depends on your ability and confidence level in your dealership.

Several who have installed the segr have noticed a much longer warmup time in cold winter temps (<20*F)and a far more rapid drop in the coolant gauge when idling at stop lights. Loss of egr heat into the engine is the major reason.

vtdog · **Joined:** Fri Sep 30, 2005 11:27 am **Posts:** 640

There was a TSB out on "false" high temp readings under load for 05s. It had something to do with the temp sensor needing a re-program. I don't remember exact details of the fix, but I had it done when I first got the Jeep in 05 as I had the same issue described. There may be a past thread on the overheat TSB, but I am not sure.

zrtwooo · **Posted:** Mon Jan 05, 2009 4:59 pm

wow Ranger1 ! that was a well thought out very articulate submission! thank you!!! do you have more details on the "Block off" of the supply to the egr? what do i use? does that throw a cel? i have an appt. tues. am for the egr to be replaced...do i need it replaced if i do the block off? oh and what's a "mil"
thx
Mike

RTStabler51 · **Posted:** Mon Jan 05, 2009 5:24 pm

KeighJeigh wrote:

thers may have put in larger radiators.

- Chris

Chris - I believe our ICs are part of the radiator so I don't think putting in a larger radiator is a cost effective solution.

As someone else pointed out, have you had any of the new flashes? I had an 'overheating' condition per the gauge once but once the ECM was 'updated' I haven't had it since.

nursecosmo · **Posted:** Mon Jan 05, 2009 9:21 pm

Ranger1 wrote:

A few points worth considering and a suggestion for towing with an intermittent overheat condition:

1. If the low speed cooling is fine, not very likely to be a bad viscous fan clutch
2. High speed overheating, coolant flow is impeded or excessive heat load is building in the coolant system. Reasons could be coolant pressure isn't high enough, possibly by a bad radiator cap or the EGR valve is open too long, adding too much heat to the coolant via the EGR cooler. Out of those two possibilities, which one is known to be more problematic, the radiator cap or the EGR valve failing?

3. EGR when operating as intended, reduces peak in-cylinder burn temperatures, not coolant temps. It increases coolant temps because the ~1000*F exhaust stream is routed through an EGR cooler, cooled by your antifreeze mixture. It's relative - the peak cylinder temps are much higher than your coolant temp can ever reach.
4. EGR, if functioning properly, operates at idle (up to a couple of minutes) and very low load conditions, not while towing or at WOT.
5. Malfunctioning EGR, if stuck in even a slightly open position, may increase coolant temperatures dramatically under load for a couple of reasons:
a.) loss of boost out through the egr valve into the exhaust instead of the cylinders, reducing engine power, causing more fuel to be applied(via your right foot) than is normally necessary. More fuel = more engine heat load.
b.) excessive 1000*F exhaust flow through an EGR valve in the open position will flow through the EGR
cooler for far longer than intended, as in continuously. More speed = more exhaust heat transfered to your coolant in this case. This will add much heat to your coolant, by some estimates I've seen, as much as 40% more in a correctly functioning EGR system, with a malfunctioning one, much more than that.
6. The TSB used to install a software patch to the coolant gauge didn't fix anything related to increased cooling. For those of us who monitored the actual temps, we discovered that it changed the gauge calibration to be semi-logarithmic around the 12 o-clock position.

If you're going to be towing and don't have time to get the EGR valve replaced, put a block off plate on the egr feed tube where it enters the egr valve body. You'll get a MIL, but not a limp mode from this mod and it will eliminate any cooling issues caused by excessive heating of engine coolant by an open egr valve.

If you still have high speed cooling problems after blocking off the egr supply line, then you have either a coolant thermostat problem or other cooling issue. Either way, you can isolate it by blocking the EGR valve supply line. If the problem suddenly disappears, you've identified the cause. If not, you've eliminated the most likely suspect in order of probability.

This can be useful if your not comfortable with the dealer working on your CRD just before taking a long trip with a trailer attached. It depends on your ability and confidence level in your dealership.

Several who have installed the segr have noticed a much longer warmup time in cold winter temps (<20*F)and a far more rapid drop in the coolant gauge when idling at stop lights. Loss of egr heat into the engine is the major reason.

Good article Ranger. I'd like to address point 1 and 5 though.
point 1. Low speed cooling is not "usually" affected in a DI diesel vehicle by a malfunctioning fan clutch unless there is a steady heavy load on the engine such as a steep rocky climb or pushing through heavy snow etc... The reason being that the viscous clutch is never locked up unless there is a high heat load being put into it through the radiator. The rest of the time it is just free spinning but still moves enough air through the radiator for sufficient cooling. A malfunctioning fan clutch will be more noticeable at mid range to high speeds if the lockup does not engage when there is a higher load on the engine. Even at highway speeds not nearly enough air is going through the radiator on its own for sufficient "high load" cooling to occur.

Point 5. Boost can NEVER flow backwards through the EGR valve. The pressure differential between the pre-turbo exhaust and the CAC flow is ALWAYS at least 2:1. While it is not impossible that the EGR may be stuck open, if it were stuck in a wide enough position to significantly raise ECTs the symptoms would almost certainly include significantly reduced power and VERY noticeable black smoke from unburnt fuel (especially under high boost). Of course stranger thing have happened.

The coolant cap would certainly be possible cause for low coolant pressure as you mention, which could cause overheating under load and the EGR block off is always a good idea. The overheating could be any number of things but I still vote for fan clutch.

I love this stuff. Especially when the problem is with someone else's vehicle (Sorry for your troubles guys).

nursecosmo · **Posted:** Mon Jan 05, 2009 9:23 pm

RTStabler51 wrote:

KeighJeigh wrote:

thers may have put in larger radiators.

- Chris

Chris - I believe our ICs are part of the radiator so I don't think putting in a larger radiator is a cost effective solution.

As someone else pointed out, have you had any of the new flashes? I had an 'overheating' condition per the gauge once but once the ECM was 'updated' I haven't had it since.

The IC and the radiator are two completely separate units.

Turbo Tim · **Posted:** Mon Jan 05, 2009 11:48 pm

Zrtwooo, first be very careful what the dealer does! You don’t want them to reflash your engine cpu and you end up with reduced power (otherwise known as the F37).

If your CRD has already been neutered, then it don’t matter.

First question is: Is it really overheating? You need a temperature measuring device to verify EXACTLY what the temperature is. The dash temp gauge is not accurate (thus the dealer reflash to correct the calibration of the dash gauge).

If you are getting bogus answers from the dealer, PM me and I have an Autoenginuity Scan tool and a hand-held digital thermocouple and we can compare what the real temps are to what the computer reports them to be.

My CRD runs a high fever too in the summer when I pull my 19’ boat out to Lake Pleasant, in 117* degree summer heat with the air conditioning on @ 70+ MPH. I suspect my fan clutch is bad and will replace it this summer when I have everything hooked up so I can compare back-to-back the before and after effects of replacing the fan clutch. To be continued…….

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Quote:

Point 5. Boost can NEVER flow backwards through the EGR valve. The pressure differential between the pre-turbo exhaust and the CAC flow is ALWAYS at least 2:1. While it is not impossible that the EGR may be stuck open, if it were stuck in a wide enough position to significantly raise ECTs the symptoms would almost certainly include significantly reduced power and VERY noticeable black smoke from unburnt fuel (especially under high boost). Of course stranger thing have happened.

I'll have to disagree with you on this one (especially the word NEVER) based on my first egr failure. The egr valve is connected between the intake post turbo and the exhaust manifold pre-turbo as you stated. But, I have had an egr failure where it stuck open, produced huge black clouds of smoke, very low power, very noisy combustion, extremely poor fuel economy (14 mpg as read on the EVIC) and and a low boost code (CEL/MIL) light on the dash. My wife following me to the dealership told me that the exhaust was a huge solid black swath as wide as the CRD itself and 10 feet long. That is definitely low boost and overfueling. This occurred around 8K miles.

If the pre-turbo exhaust pressure was 2X greater than boost at all times, a low boost code, loss of power and over fueling would not have resulted because the boosted fresh air would have been forced into the intake plenum and the air fuel ratio would have been correct. If the low boost code is set via map sensor readings by the ECM, it won't be able to distinguish between pressure generated by exhaust gas or fresh air boost in the intake manifold. The fact that the boost pressure went low with an open egr valve tells me that the pressurized air and exhaust gas combo was exiting via the path of least resistance - the open egr valve, back into the exhaust manifold and out the tail pipe. Nothing else changed, the engine was mechanically sound, the turbo was good, the CAC and hoses were good, the only change to the system was the open egr valve. With a 2X exhaust to boost ratio, exhaust gas would be blowing out of the air filter box.

Also, I would think that if the exhaust pressure is greater than boost by 2X at all times, an AFC valve should not be necessary in order to draw enough exhaust gas into the intake plenum. The exhaust gas at that pressure differential should be the first gas entering the cylinders.

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