Counting on some local knowledge

[coop77]

Hi guys-

I've got an 86 FJ60 that I've owned a little over a year now and most of that time has been out of service or in the shop. The final obstacle I'm facing is an overheating problem we can't seem to get fixed.

It's got a mild 350 in it and we've put a fairly large 3 pass radiator in it this week, swapped the heads/gaskets, changed thermostats, and just about everything else I can think of and it's still overheating. Timing and AF are set correctly, it has 3" exhaust so should be no restrictions there, shroud is on fitted and sealed... What am I missing? Motor is only .30 over.

Mostly this happens at highway speed (getting up to 230-ish), but can occasionally happen in traffic or sitting. I'm putting a clutch fan on tomorrow as a last resort but beyond that, I'm totally stumped. Definitely worse with AC on.

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[warpdriv]

What is the timing set at? What is your thermostat temperature rating? What is the 350 out of? Are the fan blade sticking halfway outside fan shroud?

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[green grass hopper]

Hi guys-

I've got an 86 FJ60 that I've owned a little over a year now and most of that time has been out of service or in the shop. The final obstacle I'm facing is an overheating problem we can't seem to get fixed.

It's got a mild 350 in it and we've put a fairly large 3 pass radiator in it this week, swapped the heads/gaskets, changed thermostats, and just about everything else I can think of and it's still overheating. Timing and AF are set correctly, it has 3" exhaust so should be no restrictions there, shroud is on fitted and sealed... What am I missing? Motor is only .30 over.

Mostly this happens at highway speed (getting up to 230-ish), but can occasionally happen in traffic or sitting. I'm putting a clutch fan on tomorrow as a last resort but beyond that, I'm totally stumped. Definitely worse with AC on.

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are you using a fan clutch? if so does it work? how are your belt? do you have a rev. water pump?

 

[coop77]

OK, so to update a bit- yesterday I spent basically the entire day removing the flex fan (though my knuckle skin may have now clogged the fins of my radiator) and finding an OEM dual fan set up that would fit. After much trial and error, I found that a 99 Dodge Caravan fan fits this 26X18 core like a glove after grinding off a couple of the plastic mounting tabs. These fans move a TON of air.

I also verified with both mechanics that the water pump is correct. I am still having weird spikes in temp on the short test drive I did last night. I am going to check for air this evening and probably replace the soft feeling top hose.

Other than that, I'm back to stumped.

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[warpdriv]

Let us know. If it is still getting hot, can you please answer the questions in the previous posts so we have a better idea what we are dealing with?

 

[jmdaniel]

Maybe the sending unit for the temp gauge is bad. I don't see that you stated you checked that.

 

[coop77]

OK, do no joy on the cure... I even had something happen that's never happened previously, the high pressure valve on my AC compressor popped off! I just had that checked/filled on Friday, so I'm puzzled about it.

I did notice that the fans often don't kick on till about 210 and they're supposed to come on @ 180. I put the probe at the very top right corner by the return thinking it was the hottest spot and the easiest with the electric fan shroud. This thing can idle @ 170 with those new fans all day, but the minute you start driving it, it starts climbing up there. I haven't done a long highway run to see where it would get to, but I've pulled 220 on short trips. The odd thing is sometimes, not every time, it'll cool right back down if you turn the AC off and on. Other times you can turn it totally off and it still overheats, but not as bad. It's just so erratic. It was also about 25 degrees cooler yesterday which probably helped a lot.

Is there any way possible the AC could cause this? I know it sounds dumb, but it just seems to keep throwing itself in the mix randomly.

For the previous posters: it's a mid 60's 350 .30 over. The guy who built it set the timing so I don't know where it is, but it runs and starts well. Thermostat is a 165, but I've tried several and even just a hollowed out restrictor.

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[davegonz]

Get a cheap Harbor Freight infrared thermometer and check the temps on the radiator and see if they correspond (somewhat) to your gauge.

I'm wondering if your AC valve blew because the evaporator just couldn't dump enough heat and the pressures climbed as a result.

 

[ajordan1975]

There's no air in the cooling system right?
Easy way to do that is turn heat on high. Watch for bubbles to stop in the radiator.

 

[coop77]

I've tried to purge the system as best I can doing exactly that... I even put in a "T" on the highest heater hose (well above the engine) and filled the rad with that open until it flowed out.

I've put it in the hands of the guys over at LC Specialists... They seem to really know their stuff and I have high hopes for a resolution.

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[coop77]

Get a cheap Harbor Freight infrared thermometer and check the temps on the radiator and see if they correspond (somewhat) to your gauge.

I'm wondering if your AC valve blew because the evaporator just couldn't dump enough heat and the pressures climbed as a result.

I think you may be exactly right... Odd thing is, I was idling through a field at the dove lease and the temp was only about 185 when it happened.

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[warpdriv]

Well a couple of things.

The condenser is going to put off heat and that heat goes into the radiator.

When I was having some cooling problems with my 40 (SBC 350), Edwin (aka green grass hopper) told me that I did not have a hot enough thermostat and told me to put a 195 in. I did an no problems with cooling. The reason for a hotter thermostat is that it is suppose open and close so that the coolant stays in the radiator longer to cool down. So in my case, when I start my cruiser and the engine gets above 195, the thermostat opens the coolant from the radiator flows into the engine and the hot coolant from the engine flows into the radiator. Since the coolant flowing in from the radiator is cooler than 195, the thermostat closes and therefore the hot coolant in the radiator spends more time there. Then the cycle repeats itself. Hope this makes sense.

 

[coop77]

Well a couple of things.

The condenser is going to put off heat and that heat goes into the radiator.

When I was having some cooling problems with my 40 (SBC 350), Edwin (aka green grass hopper) told me that I did not have a hot enough thermostat and told me to put a 195 in. I did an no problems with cooling. The reason for a hotter thermostat is that it is suppose open and close so that the coolant stays in the radiator longer to cool down. So in my case, when I start my cruiser and the engine gets above 195, the thermostat opens the coolant from the radiator flows into the engine and the hot coolant from the engine flows into the radiator. Since the coolant flowing in from the radiator is cooler than 195, the thermostat closes and therefore the hot coolant in the radiator spends more time there. Then the cycle repeats itself. Hope this makes sense.

Well, he's got it now and I'll be happy to try anything he suggests.

It's tough to have nearly $25K in a rig that you can't even drive, and no end to the spending in site!

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[Lake Rat]

I run a 190-195 thermostat in my SBC350 in my 40 (trail truck) it seems to cool good. The only time it over heats is if there is an air bubble in the upper hose (the arc of the hose going to the housing is a little higher than the radiator cap, so I have to wiggle the hose after initial start up) If you have the fast burn heads in your truck (4 bolts holding the valve cover on) you will need at least a 190 thremo for the motor, 165 is a little cool for these motors. I would try that first myself. You may also, want to get an after market temp guage and install it under the hood somewhere and check your dash guage with it to see if you may have a guage or sending unit problem.

 

[meatloaf]

Well, he's got it now and I'll be happy to try anything he suggests.

It is in good hands now.

It's tough to have nearly $25K in a rig that you can't even drive, and no end to the spending in site!

I feel your pain...

 

[ajordan1975]

Besides the point but add some hood louvres. Any thing will help at this point I assume.

 

[coop77]

Well, I haven't gotten a chance to do a ton of testing, but it looks like Edwin and his crew exorcised the demons! (pretty sure they put a 50/50 blend holy water:coolant)

So apparently the temp sensor in the head was right by, as in just damn-near touching, the exhaust manifold. It was relocated to the intake.

Also, and probably more importantly, due to GM and Toyota design differences, the water wasn't really circulating to the back of the block. They put in a brass "T" and a bypass hose.

Not a ton of testing, but so far nothing over 195-200 in traffic or on the highway with the AC running! So glad to be in the road again!

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[davegonz]

Good news.