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Not overheating...but running warm

P

pipewrench

NAXJA Forum User
Location
GA
I think I have finally gathered up enough clues to think my head gasket is failing, just want some advice.

When driving on the interstate, temp will slowly creep to around 220. (Between optimal and the next mark on the gauge) Once you get off and get on back roads, it will come back toward 210. Also it should be noted, my coolant needs topping off every so often.

New thermostat, and the coolant has been flushed several times. It doesn't overheat at idle.

I bought a block tester kit from napa, but the results were kind of strange. The dye did turn from the dark blue to a green tint. Not full on yellow.

There is zero smoke, zero oil residue on filler cap, no traces of oil in coolant or coolant in oil.

Am I over reacting to this temperature rise and need to figure if the radiator is clogged or a flow problem? Electric fan kicks on as it should.

My brain is thinking the slow temp rise is due to a small head gasket issue. When you're in the throttle hot exhaust gas is getting in the coolant and it can't reject the heat. Strange that theres not obvious oil in coolant though.


Any advice is appreciated, I have read lots of threads on this but seems like every situation is slightly different.

1999 4x4 Auto
134k 4.0
 
If you weren't seeing coolant consumption, I'd suspect a coolant/air flow problem.

If you using coolant and don't see any signs of external leakage from the water pump, hoses, radiator, etc., then you're burning it/small amount may be getting into your oil. By the time you see coolant in the oil there is a significant problem. Head gaskets can blow any number of ways and one of the ways cause temperature problems. You should plan on pulling the head and checking the head gasket/inspecting the head for cracks. Also make sure the condenser/radiator are free from dust, dirt, and bugs that could restrict airflow. Check the water pump impellers.
 
I agree you're heading in the right direction with your diagnosis, but lets rule out a couple other simple items. Have you pressure tested the cooling system and the radiator cap? How old is the radiator cap for that matter?

Also, I know it typically presents itself during warm idle, but have you checked your fan clutch? They tend to fail on our vintage XJ's and can cause a slow creep in temps.

Perhaps a leak down test would be a good step, or sending your oil out to have it analyzed would tell the tale. I wouldn't want to pull the head unless I absolutely had to.

I thought I was consuming coolant awhile back and ended up finding a slight seap at the t-stat housing. It would leak only during warm-up, not when it was hot or cold. This was enough for me to notice a slight drop in coolant with no overheating or other symptoms. I guess the point I'm trying to make is the coolant can leak in a lot of areas and I'd want to check them all before I condemned the head.
 
If temp creeps up at speed, typically mech. fan clutch is failing.
 
I had a similar issue where my 98 xj would overheat while on the highway. Turned out to be a semi clogged radiator, which took me a while to figure out. Since I could tell coolant was moving, I thought that this was indication that the water pump was cycling the coolant and I thought that there wasn't a blockage since it was moving.
 
head gasket is a possibility, but i'd look at the radiator closer before acting on anything. is it old with the "red" brittle areas on the fins? plugged up with dirt/bugs/crap? maybe the fins on the Rad or the a/c condenser are damaged and flattened out?
highway is not where clutch issues will show themselves, you'd see a rise when you got off the highway and decreased the airflow thru the rad.
 
Wow thank you for all the replies, I'll try to answer all the questions as best as possible.

Have you pressure tested the cooling system and the radiator cap? How old is the radiator cap for that matter?
Click to expand...
I have not pressure tested the cooling system but sounds like a great excuse to buy a new tool. I replaced the radiator cap less than two months ago, actually before these symptoms started. I think the cap I have is 15 or 16 psi, its one of the safety type with a lever on top.

I have tried checking the fan clutch using some tactics described on the forums. I wasn't sure so I went ahead and bought a ZJ clutch (not max cool) I'll be putting it on this week with work and weather permitting.

I actually have a oil sample kit laying around somewhere from blackstone labs I use on my diesel, so I'll send one out. May be next week before I get around to it too.

is it old with the "red" brittle areas on the fins
Click to expand...
I'm not sure about this but will try to let you know. I plan on getting up close and personal with the radiator as soon as I get a chance.

I'm thinking I want to find the Delta T between entering and leaving with thermostat open, that could help identify low flow I'm sure. Also, I want to look for cold spots as someone mentioned on a thread to help me identify if the rad is clogged.


I'll do some searching to see if acceptable temp drop across radiator. Forgot to mention.....I do have a winch and smittybilt bumper with bull bar and light bar in front of radiator.....however, it was okay like that until recently.

So many variables in a problem like this. Thanks so much for all the feedback.
 
One thing I wanted to add, I'm using green peak antifreeze.

I also replaced upper and lower hose. New lower hose didn't have spring. Old spring was nasty looking so I didn't use it. I have monitored lower hose while at operating temp and while having motor revved and haven't noticed any collapsing.

If (When) I end up draining system again I'll put the spring in. I'm really considering changing water pump and radiator, then every component will be new. I'm just not a fan of throwing parts at things when some diagnostics can be done first.

With that being said, mailing oil sample off is going to top of the list.
 
Ok guys, I am still waiting on my oil analysis to come back. In the meantime I did some testing with a IR thermometer. (Sorry for this long post, just wanted to provide the gurus with lots of data)

First, I'll describe my trip. I idled from a cold start and logged temps after warmup.
I drove 5 miles of back roads to a gas station and logged temps. Then, I drove 5 miles on the interstate, pulled over and logged again. Lastly, I drove 5 miles of back roads home and logged a third time.

I need some help here because now I'm more confused than before.

Idle after warmup:
Heater Hoses: 180*
Upper rad hose: 153*
Lower rad hose: 140*
Tstat housing: 209*
Gauge showing hair below 210*
Aux fan off

5 miles of backroads before interstate:
Heater hoses: 190*
Upper rad hose: 176*
Lower rad hose: 151*
Tstat housing: 212-216*
Aux fan on
Gauge reads hair over 210*

5 miles of interstate:
Heater hoses: 197-210*
Upper rad hose: 186-190*
Lower rad hose: 165*
Tstat housing: 232*
Gauge was barely below next mark after 210
Aux fan on

Lastly, 5 miles of back roads back home:
Heater hoses: 199-210*
Upper rad: 184*
Lower rad: 162*
Tstat housing: 224*
Gauge hair over 210*
Aux fan on

Ok, so I am dropping about 25 degrees between the upper and lower radiator hoses.My reasoning says the thermostat is open, and the radiator is rejecting heat. The question is...is 25 degrees enough?

Another confusing item is my thermostat housing will be 40-50 degrees hotter than the upper radiator hose. Is this because the metal housing is reflecting temps better or not moving the water out? Hard to believe 5 inches of hose would have a 40-50 degree discrepancy.

I'm going to tackle the ZJ clutch fan tonight even though I don't think thats the problem. It doesn't overheat at idle. When cutting it off, I noticed the clutch fan made many rotations before stopping. Can't remember if that was bad or not.

Again, sorry for the long post and help is very much appreciated.
1999 4x4 4.0
31'' tires automatic
 
I think 40 degrees is more typical of a healthy radiator, 25 sounds low. Check fin condition and use a chemical flush to see what comes out of the tubes. May need a new OE style replacement radiator
 
I have chemically flushed numerous times, fins don't really look bent. I didn't know what to expect as far as temp drop. I thought 25 sounded pretty good but didn't have anything to base it on.
232 degrees at the thermostat housing is what has me worried. Are you thinking my lower hose after radiator should be a lot cooler? 165 seems like a decent number to me, but have no idea.
 
Fan that spins to a stop, especially when hot is BAD. That thing should be locking at any temp over 170, IIRc. Remember it's reacting to the air flowing through the radiator, and radiating off the motor. T-stat housing should be the hottest. Inspecting the pump would also be a good idea.. IF you are having reduced flows, the causes will be plugged radiator, stuck T-stat or pump. slight unnoticed leaks are also common to pump going bad.
 
The fan did slowly spin to a stop with the motor hot. I just finished putting the ZJ clutch in and did the same test drive. All temps much cooler except thermostat housing, it was still about 220-225 degrees. Ambient temperature was also about 66 as opposed to 80 during the first test.

I just hope the new clutch didn't just cover up another problem.
Also, the new clutch fan stop immediately when the motor stopped. However, the motor wasn't as hot.

My dad has a 2000 XJ, I'll drive his one day this weekend for a comparison on the housing temperature.

If mine stays cool on the next warm day maybe the problem is solved. I am still very eager to see the oil analysis though. Thank you everyone for helping me through this.
 
I have not, but that's a good project for one night this week. I drove it today in 80-85 degree temps.
Same scenario, optimal or a hair under until you get on the interstate. Then it runs a hair over 210 until getting off. Within a few miles off interstate its back to 210.

I'm hoping the oil analysis will be back this week, I'll pull the plugs one at a time tomorrow or Tuesday in the meantime for some more information.
I think I read on a thread a while back that if coolant is contacting the plugs they will be very clean...as in steam cleaned. Is this correct?
 
pipewrench said:
...I drove it today in 80-85 degree temps.
Same scenario, optimal or a hair under until you get on the interstate. Then it runs a hair over 210 until getting off. Within a few miles off interstate its back to 210...
Click to expand...

This really points to insufficient water flow. On the interstate you know the problem isn't airflow (unless fins are bent / clogged in condensor or radiator) because you've got a 65 mph breeze through the grill. This pretty much just leaves water flow.
You could remove the upper & / or lower hose & see if you can put an eyeball on the radiator tubes, if they look gnarsty they are probably jammed up.
 
That wouldn't surprise me. When I got the jeep the coolant looked like coffee. The water pump has been on there a long time I'm sure, if I end up replacing it and the vanes are worn I'll try to get a picture up here.
As far as the radiator, I tried to take my IR gun to look for cold spots as someone on here suggested to me. It was however pretty hard getting in there to multiple places. Seeing the temp drop across it did give me some hope though.

In your opinion yossarian, do you rule out my theory of a minute head gasket leak? That the combustion gas gives off more heat at higher RPM's than the radiator can reject to atmosphere.

If the oil sample comes back and says no coolant in the oil I'm going to bite the bullet and replace water pump and radiator at the same time.
With that being said, I've read its hard to beat a Napa water pump. So that will be what I go with.

Whats the current consensus on radiators? I have read tons of threads about them.
However, a lot of people said they still have to replace higher quality two and three row radiators within a short time span. I don't recall how current these threads were either since I searched for them.

Whenever this goes down, I'm going to delete the A/C condenser as well since I bypassed my A/C due to clutch failure. Maybe that will free up some airflow as well.

All in all, I know I should probably go ahead and do the water pump and radiator if I'm going to keep the jeep. In reality though, if I have a head gasket problem I won't want to invest the time or money in it to repair it. (Mostly money since head gasket replacement is probably over my skill set). I would probably pass it on to a family member or sell it to someone that wants to fix it.
It'd be time for another XJ or maybe a TJ this time.
 
OK. A few thoughts here. I'll try and keep it organized.
The coolant consumption is quite possibly just a slow leak. I had one that mystified me for a long time. Turned out to be a seeping thermostat gasket & the coolant just steamed off the hot cylinder head before it dripped.
It could also be a head gasket issue or a cracked head. This isn't very likely but it is possible. The best way to rule it out is to have a competent shop use a 5-gas analyzer (smog sniffer) to sniff your coolant for traces of combustion gases and / or hydrocarbons (unburnt gas). Anything above 5 parts per million in hydrocarbons, the head gasket is leaking gasses into the coolant. An engine that is burning coolant will also contaminate the coolant with exhaust gas. It shouldn't cost much to have them test it. While I was working in a shop, I didn't really bother testing head gaskets any other way (unless it was obviously puking coolant / white smoke from the tail pipe). Anyway, bring it to a shop that has a smog license and they should have the equipment to test this properly.
The consensus is "May as well get a 3 row, all metal!" but as you said, lots of those get replaced every few years. Personally, I don't see plastic as such an awful thing - I've got 150K on mine and, what, 16 years now. No leaks, no cracks. If I was going to buy a radiator, I'd go on Rockauto.com and get the Nissens radiator or the Spectra. I've installed a lot of Nissens and never had a problem.
When you do the water pump, look carefully at the hoses. It's almost definitely worth replacing them, upper & lower both.
Summary:
Unless you or somebody else overheated the piss out of it, you probably don't have a head sealing issue - but it's worth a few bucks to check with a decent shop.
Replace your radiator with a Nissens for $100 on Rock Auto, throw $25 in hoses and $25 in coolant on top of that, add in $40 or so for the water pump, $5 for a radiator cap.
Clean all making surfaces *really* well, use a gasket sealer (not RTV. Gasket sealer) and a torque wrench.
Update us with what happens.
 
yossarian19 said:
OK. A few thoughts here. I'll try and keep it organized.
The coolant consumption is quite possibly just a slow leak. I had one that mystified me for a long time. Turned out to be a seeping thermostat gasket & the coolant just steamed off the hot cylinder head before it dripped.
It could also be a head gasket issue or a cracked head. This isn't very likely but it is possible. The best way to rule it out is to have a competent shop use a 5-gas analyzer (smog sniffer) to sniff your coolant for traces of combustion gases and / or hydrocarbons (unburnt gas). Anything above 5 parts per million in hydrocarbons, the head gasket is leaking gasses into the coolant. An engine that is burning coolant will also contaminate the coolant with exhaust gas. It shouldn't cost much to have them test it. While I was working in a shop, I didn't really bother testing head gaskets any other way (unless it was obviously puking coolant / white smoke from the tail pipe). Anyway, bring it to a shop that has a smog license and they should have the equipment to test this properly.
The consensus is "May as well get a 3 row, all metal!" but as you said, lots of those get replaced every few years. Personally, I don't see plastic as such an awful thing - I've got 150K on mine and, what, 16 years now. No leaks, no cracks. If I was going to buy a radiator, I'd go on Rockauto.com and get the Nissens radiator or the Spectra. I've installed a lot of Nissens and never had a problem.
When you do the water pump, look carefully at the hoses. It's almost definitely worth replacing them, upper & lower both.
Summary:
Unless you or somebody else overheated the piss out of it, you probably don't have a head sealing issue - but it's worth a few bucks to check with a decent shop.
Replace your radiator with a Nissens for $100 on Rock Auto, throw $25 in hoses and $25 in coolant on top of that, add in $40 or so for the water pump, $5 for a radiator cap.
Clean all making surfaces *really* well, use a gasket sealer (not RTV. Gasket sealer) and a torque wrench.
Update us with what happens.
Click to expand...

What he said... My bet is a partially clogged radiator.
 
Thanks guys. I ran home and got the jeep today and took it to a Napa auto care. They were the only place out of about 7 or 8 I called that do the gas analyzer as opposed to just the block check.

I didn't get a print out but they didn't charge me, so I guess I can't complain. They unfortunately saw 6PPM of whatever gas they were sniffing. They checked in the overflow and the regular cap.
Napa said not to worry about anything under 10PPM, however after seeing what was mentioned above about 5 parts per million and all the other symptoms I'm seeing I'm discouraged.
 
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