the quadrillionth overheating thread - Sanity now hanging by a thread

[Fiodh. Argus]

I'm having a frustrating over heating problem. It's the last thing on my list before the cherk is road ready.

It runs fine at idle, but as soon as I test drive it up a long grade, it just starts heating up, until 235-240 and I turn around asap and glide back to the house while it cools down.

I can't figure it for the life of me. I've put in a new aluminum radiator and an electric fan setup from BJs. I've checked the timing and had it set at 10, then 12. Runs stronger at 12 and no difference in the heat. Hard to start when hot though. I checked the thermostat and it's installed correctly and opens in a pot of boiling water at 185. I also had a 195 but it seemed to get hotter.

Another thing I was checking was to see if the lower hose was compressing or getting sucked shut. It looked and felt like it was holding it's shape. I don't know if it has a spring in it, but didn't change on the outside. However, what was strange was that the UPPER hose from the thermostat housing to the radiator did sort of deform and close up a bit on high revs.

The only hose my local NAPA has is a universal flexible hose, are those any good?

I was wondering if that hose contracting would indicate a bad water pump not pushing enough back to the radiator? Seems to me like it must be sucking a lot of water out of the radiator and causing the engine side not to fill it up fast enough?

I put a thermometer in the radiator core at the top hose, and it read 175 - 195 while the dash gauge read 200 and 220 respectively.

Also what about the radiator cap? it's new and I have an overflow bottle that it sucks from. The cap is a 7lb cap I think. Does that really make a difference?

If it's not the water pump and not the hose then I just don't know and am worried something is amiss inside the engine, possibly a blocked passage.

Any ideas or insights would be greatly appreciated .

[skeletor]

#1 as always on these jeeps, get a mechanical guage to see if it is overheating, you said you put the thermometer in the radiator and thats not the same as the inside block temp.

the most missed part of our cooling system is the heater core, they can get blocked up and slow down coolant and all sorts of bad stuff. i would definitely get a lower radiator hose with a spring in it. with the radiator cap off can you see the coolant moving around?

Also what about the radiator cap? it's new and I have an overflow bottle that it sucks from. The cap is a 7lb cap I think. Does that really make a difference?


something around 15lb is what came stock.

good luck!

[Fiodh. Argus]

thanks Skeletor
I just checked the radiator cap and it's 16 lbs.

good to know the temp won't be the same at the radiator as in the block. I was wondering.

The coolant does seem to move around in the radiator while it's running and it actively sucks the overflow when necessary, then returns fluid to it again.

I guess a good new gauge might be in order. These are the TPI tech gauges that are aftermarket but my faith in them has been shaken lately.

the lower radiator hose is one I bought from Bjs a while back. Still looks real good. The top one, I am not as sure about but it isn't swollen or leaking.

By the power of grayskull! I will sort this problem out

[wickedwagon767]

By the power of grayskull! I will sort this problem out

yoooou haaaaaave the pooooweer!

[DEMIGOD]

Do you have good flow while looking with the cap off? I am thinking maybe the heater core may be clogged as mentioned prior.

[Fiodh. Argus]

maybe I will bypass the heater core and see if it improves. The heating works pretty well otherwise.

[drlocke]

I had an intermittant overheating problem in my Wag, and felt the heater hoses while it was in "overheat" mode, and one was piping hot while the other was stone cold. It was not a blocked core but a slipping impeller in the water pump.

[Millerluck]

I had a very frustrating over heating problem......I tried all kinds of things to fix it. Newer T-stats and new fan clutch. New spring in the lower hose..........

I had an air pocket in the block it wouldn't cough up.

I ran it for a few minutes with no T-stat and I watched thru the filler neck and this nasty burnt yellow coolant sudenly came into the radiator with a big burp. I put the t-stat back in and all was well.


Larry

[asphaltrockdweller]

This could be a problem too!
REALLY BAD MUD
http://i214.photobucket.com/albums/cc19/lightingdeziner/IMG_0486.jpg

I have to get a radiator shop completely clean out my cooling system. Of course now I have found out that my freeze plugs on the back of the heads are leaking too.:banghead: :banghead:
Maybe just do a rebuild before I put on all of my shinny new BJs stuff? I don't want to ruin that radiator.:(

[Ristow]

It runs fine at idle, but as soon as I test drive it up a long grade, it just starts heating up, until 235-240 and I turn around asap and glide back to the house while it cools down.


heating under load. have you tried the mechanical fan in place of electrics

what carburation? how do the plugs look?

[Fiodh. Argus]

Hi Ristow,
I just upgraded from a flex fan to the BJs electric set up. It was not cheap, I would prefer to use it if at all possible! I thought it would solve the problem, but alas, no luck.

the carburation is a recently rebuilt 2150 and the plugs look all right, pretty brownish- grayish, here's a photo

http://www.fiodh.com/cherokee/sparkplug0909.jpg

I apologize, I should have posted this in the tech forum, accidentally it went in general discussion.

engine was rebuilt 1000 miles ago (two years however) and the radiator is a new aluminum, so I am guessing and hoping there's no goop in the system. I am going to test the heater hose bypass today and then start considering a new water pump. This one looks good on the outside, real clean, newer, can't remember if I ever replaced it.

[Ristow]

if i were in your shoes,i'd pull the electric fans,put a good stock type on and see what happens. heating under load as you describe is the first sympton of a weak fan. those electrics may not be up to the task in your case.


plugs look good. a tad rich even.

[FSJ Guy]

If you're going to replace the electrics with a regular belt driven fan, see my sig links for an optional fan clutch that might work for you. Clearance is tight, so you'll have to see if it'll fit with your application.

[Fiodh. Argus]

God these things make me want to pull out my hair, if I had hair! This is ridiculous - today I start her up to check if the heater core is flowing through - the hoses start to get warm on both sides, I rev the motor a bit, then progressively a miss develops and it starts back firing through the carb and now I have what sounds like a rod knock in #2 or #4. I just had this motor rebuilt 2 years ago and have hardly driven it since, haven't really overheated it much and have been very careful not to redline, never even taken it over 4500 rpms.

I guess now I am pulling the heads to see what's going on, dead valve, or also pulling the pan to see if a bearing has gone south.

so much for my hopes and dreams of actually registering and driving this &%#@ jeep!

can't win for losing it seems.

wish I could do a cummins swap too, they seem to be great.

[SnowShoe]

I had simular problem after installing a flowcooler water pump, BJ's aluminum cross flow radiator, and BJ's electric fan setup plus a rebuilt 2150...

I just rebuilt the carb and adjusted my air needle valves out 3 turns...and problem solved...Now, even in Texas heat with A/C running and a 160 degree thermostat...my temp gauge shows 1/2 between green and half way to to the middle of the gauge...I think I was running way lean before...so might try to richen her up a little and see what happens.

Just a thought

[Fiodh. Argus]

Thanks Showshoe, I did turn those screws out they are at 3.5 turns, a bit farther out then best lean idle at 2.5 - 3 turns. There was a lot more power off the line when I did that. Wish it was the answer to the problem though.

this knock thing has really got me upset.

[djongeward]

My problems are similar, but due mostly to living 200 ft below sea level in 120 degree heat. I have the BJ's set up as well. Some things that have helped me: 20 lb cap (look up cross flow rads)
Distilled water + Water Wetter
small puller fan behind the tranny cooler
remote oil filter and cooler combo from Bulltear
Holly ORA 475 cfm carb so I can change jets
recurve your dizzy and limit total advance

Reading more on crossflow radiators helped me. BJ's, God bless em, don't give enough info on the crossflow tech differences. I'm currently running no stat and it still will idle at 190. I'll have to put in my 180 in winter. Has to be a high flow type. My engine is built up a bit which also equals more heat.

[djongeward]

If you're going to replace the electrics with a regular belt driven fan, see my sig links for an optional fan clutch that might work for you. Clearance is tight, so you'll have to see if it'll fit with your application.

There isn't a lot of clearence between the crossflow type rad and the engine. He may be stuck with an electric.

[djongeward]

Do you have good flow while looking with the cap off? I am thinking maybe the heater core may be clogged as mentioned prior.

Tell us more about heater core and overheating. Anyone?

[Chevelleguy]

While the heater core shouldn't be necessary for proper cooling, it should help cool the engine (very little) as it is essentially a small radiator.

[YellowJeep]

In my opinion, you really need to see if the system is holding pressure. If the system doesn't hold pressure, cooling will be affected significantly. A pressure test will also rule out failed headgaskets, which seem to be popping up more often now.

What is the thought with the fan? If the vehicle is moving, there is air going over the radiator and the fan becomes somewhat useless. Hence the idea behind a clutch fan.

[Fiodh. Argus]

well at this point I don't know what to do - the knocking noise and dead cylinder betray worse problems than over heating. heck for all I know that is why it was overheating anyhow, too much friction or something.

I thought the crossflow radiator was supposed to reduce temps considerably but it made no effect, neither did the electric fan.

As an aside, I've got a buddy with a 327 in a 65 Chevy truck and he's got a three core radiator with a flex fan over an inch away from the core, no shroud, and it still never gets even hot. what's up with that!!

I guess I am going to pull the valve cover and see if the push rods are OK and then maybe pull the pan and then the head.

anybody got a 401 sitting around they don't need?

[Subic Jeep]

Try this, make a washer for the thermostat housing that has the same hole diameter as the thermostat hole. An old thermostat with the thermostat valve removed will work. This solved my sbc 350 overheating problems.

I was skeptical about this at first, but it works (tropical climate) the engine is now too cool 70-80C

[Chevelleguy]

What is the thought with the fan? If the vehicle is moving, there is air going over the radiator and the fan becomes somewhat useless. Hence the idea behind a clutch fan.


The reason for a fan clutch is so you don't overspeed the fan. The rigid, metal blade fans are not supposed to turn over 4500 rpm. They also draw a lot of power at the higher speeds.

[Ristow]

the fan pulls vastly more air through the radiator than you get solely from vehicle speed.

[djongeward]

Agreed. The fan behind the tranny cooler made a significant difference and I think it is helping to ferry air through the main radiator. That is the only conclusion I can come with as to why it helps at high speed too. I really don't think my wag has enough flow due to the design. Installing an OEM air dam also helped me, but my wag is still stock tail-dragger hight.

[Joe Guilbeau]

I will continue to stand by my receipe... read about it here with the mechanical fan, FlowKooler Water Pump, Distilled Water and Water Wetter, Prestolite Rust Inhibitor, 16-lb Radiator Cap and a Robert Shaw modified thermostat.

San Antonio,Texas has had 50-plus days this summer of 100-degree heat this summer and my Jeep's Temp Guage just gets to the Green
(190 Deg F), and stays there in traffic and on the road and towing trailers.

I do have a custome copper radiator 5-row industrial core, based on a Modine 581 size pattern.

Pure water with no anti-freeze helps alot.

http://oljeep.com/rad/edge_radiator.html