Stroker running hot

[vwtipeii]

Ok... so I have fixed many of the issues (or have had friends and mechs fix) on my lil YJ. I took her out for five days this weekend up to the mountains in Nevada about 100 miles North East of Bishop off highway 6. I was with a group of other Jeeps so I have some reference. The issue... she runs hot when climbing. The higher the elevation. The hotter she gets. I run 91 octane fuel all the time and when the engine gets hot she starts to ping. To avoid the pinging I ease off the throttle and slow down... long story short she was running pretty much all five days in the red or just below the red on highway climbs from 4000 to 8000 feet in elevation. Heck she started getting hot climbing the 405 leaving LA.

Here is what I have done to her cooling system:
1. New Griffin high flow radiator
2. 5 month old high flow water pump
3. New (Friday 160 thermostat)
4. New temp sending unit to the computer and to the gauge
5. Flushed entire system three months ago, Wednesday and again Thursday
6. Added Royal purple "ice" that is supposed to lower the temp by 20 degrees
7. Fan clutch is a year old and seems to be working fine (fan is pulling)
8. I have a small pusher fan in front of the radiator that also seems to be working fine (pushing)

Some things I have noticed is that the coolant becomes a rust color very quickly and there were some chunks of rust sitting on top of the tubes that flow the coolant when you look in the filler of the radiator. The head is about six months old. Engine is about 1.5 years old and has about 5,000 miles on it.

i have a stroker... and strokers are known for running hot. However I should be able to keep up with traffic, not have pinging and not have to run my heater when it is 100 degrees outside. when I drop back down to sea level (I live by the beach) the power comes back and she runs cooler since I am not climbing.

Any thoughts or ideas are appreciated. my YJ is a 94 with OBD 1.

Brett

[flatout]

Brett do you have any hair left on your head. I would check the rad from what you are saying that you see rust flakes on top of tubes and
having the head off a couple times maybe some of the tubes are pluged. The rad. i have found pluged had a lot of temp change from top tank to bottom tank. Check the rad. for bubbles in the fill neck when running also.

[Mitch]

Brett, I did those same things on my 88YJ and the running hot thing went away. Hope you figure it out.

[aw12345]

Like Fred said check radiator for junk and gunk. If the rebuilt engine was cleaned out well when built there should be none.
Good fan shroud helps cooling a lot also. Most aftermarket fanclutches are junk. Finding a heavy duty one and a bigger fan might do miracles for it or try a Volvo Electric fan. Or simply find a competent mechanic and have it fixed, it's fixable

[6spdYJ]

Let's dispell the myth that "strokers" run hot. That logic immediately places any Chevy small block above 265 cid into the "stroker " category as they are all longer stroke versions within the same block design. Therefore any 283, 327, 350 or 400 must run hot. Any engine with too little air flow, poor circulation, low coolant pressure, too lean, too rich or with an incorrect timing curve will run hot. The 4.6/4.7 "stroker" was originally built by VAM in Mexico as a stock motor - therefore it's not really even a "stroker". Rant over.
It's interesting that the power comes back at sea level. It's very logical due to the density of the air. But what strikes me is the MAP sensor should be reducing the pulse duration to the injectors only proportional to the density of the intake air pressure. It's perfectly normal to have a power loss due to less air density at a higher altitude, but it almost sounds like it is leaning out too far. If it isn't reading correctly due to a vacuum leak on either end of it's hose/tubing or it's not getting a full 5 volt input, the output will cut off your injectors too soon and you can run lean. It may also just be malfunctioning.
I recall you had throttle position sensor issues before. You may want to check the TPS positioning again. The TPS also plays an important role in the system. If the ECU thinks the throttle isn't open as far as it really is, it will also run lean.
Now for sheer opinion... I am not a fan of pusher fans. The reasoning is that they disturb the air flow into the radiator fins. At low speed, it's probably not an issue, but at freeway speeds, the air has to get around the fan and it's guarding before going into the fins to dissipate heat. With a puller fan, the air is already through the fins before having to get around the fan, but by this time, it's the fan's problem to move the hot air away since it already did it's job in the fins. Doesn't the grille disturb the air first? Yep. But why compound the issue?
Flatout had a very good point. The 4.0 block and head trap air when first filled. Make sure your system is FULL.
Another (and the dumbest) thing I've seen is a weak radiator cap. I've had two brand new ones fail on two different rigs. If they don't hold pressure, the water isn't pressurized against the tubes or block to dissipate heat. Everything was new, pump radiator and cap. The motor was flushed, timing was right, fuel wasn't too rich or too lean and they went straight to red. Changed the cap and everything settled back down.

[vwtipeii]

Great thoughts and feedback everyone. Danny had a good idea yesterday. The cause of the rust may be the heater core. Mine is the original. My Jeep sat for 8 years and that probably was long enough to get some rust going since everything else has been replaced. Here is the next step:

1. Bypass the heater core in the cooling system.
2. Remove the brand new Griffin radiator and have it professionally flushed/cleaned to ensure there is no remaining rust.
3. Flush the rest of the system and add new coolant and the Royal Purple "ice" stuff again.
4. Drive the heck out of it and see if she gets hot.

The pusher fan is really for the AC condenser/radiator that is in front of my Griffin. In traffic or when crawling I can't see the fan hurting however I do see the point that the air flow could be off at highway speeds.

I will keep you posted!

B

[Elusive]

I would guess that your ping is from too much compression.
I had a 4.6 stroker that I built when i was out east. Out there you can buy 93 octane right at the pump and it never pinged. When I came to CA I got the exact same problem as you are descibing wit the 91 octane.
It never ran hot..remember that 4.0's are designed to run at 210 degrees. I cured my problem by adding more fuel. I made an adjustable MAP sensor so I could richen the mixture for summer driving and lean it for winter and smog checks.

[RAT]

Hey Brett, you mentioned using the heater to reduce engine temp a bit. If the heater is blowing hot air then I doubt the heater core is clogged up with rust. But you never know with Jeeps.

[Ol Man]

You should also put your thermostat back to the 195F (I assume that is the stock temperature).

Art also brought up the issue of a shroud and I don't think you answered. That is very important in drawing air through the radiator.

[6spdYJ]

Another option to slightly reduce static compression ratio is to install the thickest head gasket you can find. You may be right at the edge of having it too high to handle 91 octane without pinging under load and having it show up in the heat. Running the 4.0 long rods with a lower piston crown keeps the piston at TDC for a fraction of a second longer and could help in building/retaining heat in the head.
The heater core can't cause overheating. What's the difference between a plugged heater core and one that has been blocked and bypassed?
Let's see a pic of the fan shroud. If the fan is too far in it will not evacuate the hot air , but just boil it around in the shroud. If the fan is too far out, it will draw air from behind the shroud and not through the fins. Without a shroud, the air is not directed through the fins and will only flow where it's easiest.
Try checking your radiator surface with a non-contact IR scanner to see if you have any hot spots - or more importantly hot rows.

[curtis]

Is the pusher fan to close to the radiator?

[Zoobi]

What temperature is it running at and is it boiling over? Have you confirmed that the gauge is accurate?

[vwtipeii]

What temperature is it running at and is it boiling over? Have you confirmed that the gauge is accurate?

It isn't boiling over. I back off the throttle right when it gets to the red... Haik said the gauge is showing about 10 degrees hotter than actual.

[vwtipeii]

"Is the pusher fan to close to the radiator?"

The pusher fan is on the mounted directly to the a/c radiator which is in front of the engine radiator.

[vwtipeii]

Another option to slightly reduce static compression ratio is to install the thickest head gasket you can find. You may be right at the edge of having it too high to handle 91 octane without pinging under load and having it show up in the heat. Running the 4.0 long rods with a lower piston crown keeps the piston at TDC for a fraction of a second longer and could help in building/retaining heat in the head.
The heater core can't cause overheating. What's the difference between a plugged heater core and one that has been blocked and bypassed?
Let's see a pic of the fan shroud. If the fan is too far in it will not evacuate the hot air , but just boil it around in the shroud. If the fan is too far out, it will draw air from behind the shroud and not through the fins. Without a shroud, the air is not directed through the fins and will only flow where it's easiest.
Try checking your radiator surface with a non-contact IR scanner to see if you have any hot spots - or more importantly hot rows.

The thought behind the heater core causing the issue is that there is a lot of rust in the coolant right away (the same day) as I flush the system. Danny ran the whole system through a machine that is supposed to flush the entire system and right after he put new fluid in a gas tank later the fluid was rusty again. When we dropped the fluid level again the next day and looked on top of the cooling veins in the radiator there were chunks of rust on top of the veins. We are thinking the only place this rust could be coming from is the heater core and the rust coming off the heater core is what is possibly clogging the radiator... reducing flow...and thus adding if not causing the over heating when I am pushing the engine hard. There seems to be enough cooling for when driving around town and on flat highway, so I have to keep trying something and then drive it out to a big hill or long grad at elevation to see if there is any impact.