360 engine overheating problems (still)

[bkahler]

I touched on this subject a month or so ago and tried everything that was suggested. In short what is happening is the faster I drive the hotter the engine gets up to about 7/8 scale.

Background info.

1979 jeep cherokee
Newly rebuilt 360 engine
Brand new radiator
Newly rebuilt automatic tranny
new fan clutch
new fan
tranny cooler in front along with rad hookup
no vacuum leaks
195 degree thermostat

We've had it back to the mechanic several times to see if he can solve the problem. He even went so far as to dismantle the engine once and found no signs of internal overheating. (fortunately) However, just driving along at around 65mph or so the temperature climbs close to 7/8 scale. He verified the temp gauge to be accurate by using a seperate gauge during a test installation. After a short 30 mile drive we pulled over and you could hear the engine coolant boiling. Very seldom however does it spit anything out the overflow bottle.

The the a/c running the overheating is even more pronounced.

The only thing that has not been replaced is the water pump. However, when we had the engine done we bought a new water pump. Prior to the rebuild the engine did not exhibit overheating problems. What we are wondering is if there are different water pumps available for the 360 engine.

Is it possible that the design was changed at some point and an inferior water pump is the result?

Needless to say we're at our wits end trying to figure this one out! Its frustrating to spend all this money rebuilding the jeep into what we hoped would be a nice daily driver and now we're stuck....

Any help would be greatly appreciated.

Brad

[KWK 1]

Have you checked your new water pump out yet? When I did a rebuild on my 258 in the cj, I used a new water pump from Auto Drone and it caused the cj to over heat. Traded it back in and got another and problem was fixed.

[bkahler]

I haven't personally checked the new pump. When the mechanic pulled the engine back apart to check things out he "said" the pump was ok. By that I assume he meant the impeller wasn't loose. Your experience tells me there could be something more than meets the eye.

We had been thinking of pulling the pump and your post tells me we probably have to do that this weekend.

Thanks for the feedback!

[joe]

Have you checked for a radiator hose collapsing?

[bkahler]

Yep, the lower radiator hose has a spring inside.

Thanks....

[jeepbob]

Amphicar! you are a glutton for punishment. I haven't seen one of those since a friend of my Dad took the nuns for a wild ride that ended up in the lake. That was also when he found out that Amphicars and road salt do not mix well...
Now if you only had a couple of DKW's (the German car not DUKW's)to go with it.
Oh yeah, have your mechanic do a check on the rad for combustion gasses as it sounds like you may have a cracked head or bad head gasket, hopefully it is not like my new motor and had a cracked block. I am still waiting for my new block to get finished.

[ September 10, 2001: Message edited by: jeepbob ]

[Ralph]

It sounds to me as if you have a leak somewhere. The coolant won't boil if the system holds pressure. The first thing I would do is to have the coolant system pressure-tested.


BTW, checked out your other vehicles. Nice work on that pickup. I went to high school in Arlington, and this gal I had a crush on had the sweetest green TR6. Wonder if it's in the hands of your friends now. I had a '74 Spitfire for a while, but I was really into Fiat Spyders and SCCA club racing, so the Triumphs were competitors. One of my mentors was a fellow named Olav Elias. I watched him build a TR3 engine with 13.5:1 CR for a car entered in F-Production, and I learned a bunch of tricks from him.

[mechanic58]

I recently put a new 360 in my wag also, did all the same things you did, new radiator, waterpump and thermostat (180) and hoses and all that stuff and I also noticed a slight tendency to overheat at speeds above 65, especially with the A/C running. My truck has the 3.31 gears in it, so I've attributed much of the problem to that, especially since I'm only running a 235/75 R 15 tire. But I have to agree with one of the other postees...you may have a leak. My radiator cap leaks and I'm quite sure that this is the cause of the problem. It'll stay cool for over a hundred miles or so, but after I've been cruising for sometime, it begins to climb. Evidence that the coolant level is dropping. Since this happened the last time, I've flushed the system (again!) and replaced the radiator cap. Took it on a 250 mile trip after that and didn't have any problems. :D

[Lindel]

Brad, how many miles have you put on the engine, since it was rebuilt? It takes in the neighborhood of 5000 to 7000 miles to break in an AMC engine, becuase of the high nickel content of the block. The rings will take "forever" to seat, until then, it can run hot, use oil, have low power, and be miserable to drive.

You might try flushing the cooling system, using the reverse flush method that Prestone recommends. They have a kit for less than $10 (I think) to do this. Basically hook it up, and run the engine till the water runs clear. This should clear the block of any loose rust or bits of metal flashing.

Another thing to check it the thermostat, it's very possible that it's defective, even though new. To test, heat it in a pan of water, on the stove, with a thermometor and see at what temp it really does open, and also watch to see if it closes up afterward.
You can also install a 180 degree thermostat, to start the cooling process a little earlier.

[joe]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Lindel:

Another thing to check it the thermostat, it's very possible that it's defective, even though new. To test, heat it in a pan of water, on the stove, with a thermometor and see at what temp it really does open, and also watch to see if it closes up afterward.
.<HR></BLOCKQUOTE>

I've had one actually close up again while still in the boiling water :(
It's a cheap-n-easy to temporarily remove the thermostat and see if it still overheats.

[igd]

Sorry, but I have to correct Ralph. It is simply not true that "The coolant won't boil if the system holds pressure".

The fact is that the higher the pressure, the higher the boiling temperature. So your coolant will boil while under pressure, but at a higher temperature than a system at atmospheric pressure.

[garcia]

A couple more thoughts -- On many vehicles its possible to put a thermostat in backwards. I wouldn't expect you'd get off that easy, but simple to check. Also, if timing is off significantly you can have overheating problems -- good luck solving your problem -- Mark

[AZtank]

similar problem...live in AZ very hot outside. Ran 3 core and 4 core radiators. both seemed to operate the same until I replaced the fan shroud, fan clutch, and water pump. Use distilled water! anyway, first it started to over heat and boil. let it cool ran system with cap off and the flushed. lots of crude built up and the system seemed to have "burped" runs ice cold now. I suggest flush it a few more times probably is a pressure issue...if everything else has been checked.

[bkahler]

Hey guys, thanks for all the replies. Sorry I didn't respond sooner. Events of the past few weeks have kind of disrupted my normal routine.

Ok, I read through all the replies and will briefly respond to each here, kind of in reverse order of when they were posted.

To AZtank - When the engine was rebuilt the block was boiled, we have installed a new fan clutch and fan. The shroud is in good condition with no cracks or missing chunks. The thermostat has been replaced 3 times so I'm assuming its been done right at least once!

Garcia - The timing has been checked and we even tried a couple of different settings with no real improvement. At least not on the magnitude that we need here.

IGD - Some how when all the parts were bought for the rebuild a 7 lb radiator cap was purchased. I noticed this problem just this weekend. I then stopped at the local parts store and asked what it should be. They said a 16 lb cap so I bought it and installed it. There was a slight improvement but the same basic problem is there, the faster you go the hotter it gets or if you're sitting with it idling somewhere it also starts to overheat.

Lindel - The engine has about 3000 miles on it so far. If anything it seems to be getting worse and not better, even with all the "tweeks" I've been doing to try and improve the cooling. I suppose we can try the reverse flush on the engine. I might save that as a "last" resort for the time being.

Matt - A friend of mine suggested the gearing might be causing the problem. I suppose it could be a contributing factor but the old engine didn't have overheating problems so I would hope to expect the same thing from a new/fresh engine.

Ralph - There are no known leaks in the cooland system. There are no bubbles in the antifreeze while running (cap off) and this is the engine has been disassembled once since the rebuild to check for internal heating problems/leaking head gasket and nothing was found. After reassembly the same overheating problem is present.

Jeepbob - I think I mentioned above there are no combustion gases in the coolant. I honestly don't know if there is a cracked head. I would have hoped that would have been found during the rebuild. I'll contact the mechanic and ask him about that one. (I'm sure his answer will be no...!)

To all - What I have done since posting my question was to replace the water pump with the original water pump. The pre-rebuild engine did not exhibit overheating problems so I am making the assumption that the waterpump was ok. Putting the old one on made no difference in the cooling effort.

As I mentioned above I also found that I only had a 7 lb cap on and now have a 16 lb cap on it with only marginal if any improvement.

We currently have a 195 degree thermostat in the engine. The last shop we took it to said it should have that. The original rebuild had a 180 degree stat in it. I was raised in Nebraska where we used 180 stats for winter driving and 160 stats for summer driving. I had originally asked the shop for a 160 and they said, no way, it should have a 195. I figured it was worth a try. It obviously made no difference. So, aside from reverse flushing the cooling system about the only thing I can think of is doing what someone suggested which is to pull the stat and see if it runs any cooler. I won't have a chance to get to this for about 2 and a half weeks from now since We're racing this weekend.

I'll post again when I have something to report. After spending all this money on the engine rebuild, tranny rebuild, A/C rebuild, cruise control installation and a bunch of other odds and ends we really want to get this dang problem fixed!

Thanks!

[Lindel]

Brad, what does the a/c condenser coil look like? Is it blocked, or does it have fins damaged?

That seems to be the one thing that no one's touched on, and can possibly be the culprit. Look on both sides of the coil, since there could be something between the coil and the radiator. If that's not it, I'm at a loss.

If the fins are damaged (bent over), there are fin combs (but a wire brush will work just as well, and is cheaper).

[bkahler]

Lindel, if my memory serves me correctly the fins are just fine, both sides. I remember spending sometime looking at them trying to deside if the problem might be in that area.

I finally discarded the idea when Susan reminded me that there was no overheating problem until the engine rebuild.

I'll look them over two weeks from now when I get back to Dallas.

Thanks!

[reddog]

I can understand your frustration. Did you rebuild YOUR block/heads or order a rebuild and swap your engine as a core? If you are hearing coolant noises in the engine I would think that you may have some kind of blockage in the block or heads. As you have stated you had no problems before the new motor. I know you said the lower hose has a spring but I would suggest that you replace the hoses if they are over a year old. It has the symptoms of bad coolant flow (although it usually cools ok at low load/RPMs) and since you have been through the usual suspects already the block/heads would be the next step.

Kerry

[ September 24, 2001: Message edited by: reddog ]

[joe]

<BLOCKQUOTE>quote:</font><HR>Originally posted by bkahler:
I finally discarded the idea when Susan reminded me that there was no overheating problem until the engine rebuild.
<HR></BLOCKQUOTE>

Brad, you seemed to have covered all the normal possibilities of overheateing. :(
Ok then was the block bored when rebuilt? If so...is it possible that it was maybe bored 0.060" over when factory recommended specs are only 0.045"? Normally you could prolly(?) get away with 60 over but...it may be too that your block may not of been 100% cast correctly from the factory in the first place and even a small overbore got a/the cyl wall(s) too thin?

[Joe H.]

Yet ANOTHER thing to check for is exhaust leaks. I seem to remember a reputable mechanic (no, really) telling me that an exhaust leak can contribute to overheating and can, in fact, blow out a radiator. I'm not sure of the mechanics (no pun intended) of that, but it's something else to cross off the list.

[2man]

I hate to make this thread any longer but seeing as I just went through the EXACT same thing, here goes. Let me preface this by saying I just had an entire over-haul. Bore .030 over and I live in west Texas so I know about heat. First we replaced fan clutch, then a new 4 core custom built "dimple tube" radiator, then adjusted for rich/lean, then added an electric fuel pump(fixed the vapor locking when truck got hot), then replaced fan shroud, next came a hi-flow 185 thermostat (and believe me this was the hardest to convince the mechanic tried everything from a 170 to a 200) but the last thing we tried was the fix : MSD distributor and offroad ignition. Once I got the timing right and the engine was firing corectly problem solved. I run 3.54 gears and QT in the summer at 104 degrees with the a/c on I stay at about 197 at 65 mph (taching about 2800). Hope any of this helps!

[Erix Jeep]

My vote would also go to low coolant flow. I know you mentioned checking the spring in the lower radiator hose, but the only time I had symptoms like that was when a dumb*ss PO had put a lower hose on without a spring. Lower hose was collapsing. If the upper hose is "soft" it may collapse too.

[Pepe401]

Here's another thought. I had a severe cooling problem with my 401 and found that my heater core was clogged so the coolant was not flowing all the way through the engine. I replaced the heater core. Once i did that it was worlds better. I have also gone to a four core radiator. Your local radiator shop can put a four core in your current radiator for lots cheaper than a new 4 row. I run a 160 thermostat in my 401 in the summer and it's always cool.

[bkahler]

As promised I'm reporting back with positive results for a change!

In my previous post I had mentioned that I had just discovered that the radiator cap was a 7 lb cap instead of the 15 lb cap that was supposed to be on it. The 15 lb cap didn't help much but that was with a 195 degree thermostat installed. Susan then pulled the thermostat altogether and the results were unbelievable. It went from running way to hot to running way to cold! That at least proved that the cooling system could handle the job. We then installed a 160 degree thermostat. Its still running too cold for my taste so we'll be trying a 180 degree thermostat sometime soon.

As near as I can figure the cure was basically to install the correct radiator cap and use a cool enough thermostat. We can't find our service manual to find out what is recommended, but the local parts store recommends a 195. That just seems to hot for me before and I still can't believe its right. I'm just happy the problem has been resolved and the jeep is running great now!

Thanks to all who offered advice and suggestions! You all kept my hopes alive while we were fighting this problem!!

Brad

[reddog]

COOL!! :D

(I crack myself up! SO witty)

Kerry

[Lindel]

congratulations!!