Engine Compartment Cooling

[OrangeCrush496]

Hey all. I'm an mechanical noob which will probably show in my wording. I got a 1973 FJ40 two years ago, and a previous owner had replaced the engine with a Chevy V8 (350 I think). I'm experiencing some issues (that I believe) are due to heat in the engine compartment, because I dont have the issues when the veicle is cold. First, the vehicle is more difficult to start when its hot. Second, the clutch gets "spongy". Third, the brakes do too...it takes too long for the brake pedal to return to "home" and for the brake lights to turn off. Obviously the brake/clutch fluid reservoirs are in the engine compartment as is the starter motor - which is why I think these symptoms are due to engine compartment heat. My questions is - how would you recommend I increase the cooling in the engine compartment? Someone suggested louvers in the hood...but I'm not a fan of that idea. The cooling fan could probably be upgraded - its a generic single speed. If you think I'm mis-diagnosing please say so.

 

[charliemeyer007]

What radiator are you using? I still have the I6 but I have a new 4 core brass one to install soon. I have a header and my engine runs on the cold side. In the winter I curtain off the lower half of the OEM radiator. Once when in low range low pushing mud with the hubs for about 20 miles I had to remove the curtain or it wanted to run hot. Lowering it didn't work it wanted full air.

Maybe add a pusher electric fan in the front of the r.

 

[peesalot]

I have a 2001 6.0 LS and use the stock radiator, mech fan, slighty modified stock shroud, cools well, runs 190, hits 200 while trail crawling, maybe 210 id its 100+ and low, low for hours. My 40 has stock inner fenders, I plated the gap from removal of steering box. The exhaust is stock gm manifolds and its wrapped about 30 inches until it gets to collector. Your exhaust is probably close to your slave. a heat shield and sleeve the hose with heat sleeve will help that & iI did a tin heat shield off the rib on firewall to keep radiant heat off master cyls & booster, with the stock louvers in that corner it seems to do well as I only experience a bit of steering fade after hard rocks all day.

 

[peesalot]

I have thought about putting a 12v computer fan under the pass side louvers to exhaust radiant heat as well, not a fan of removing inner fender.

 

[pb4ugo]

We need pics of you engine compartment, so we can see your setup. I run several 40's with 350's. They run cool. Do you have an electric fan or a mechanical fan attached to the engine? There's no need to add louvers.

 

[rlong]

Does it have headers, or chevy oem cast manifolds? Headers infamously increase the under hood temps. Many wrap them with exhaust insulation when they do (while others “yell” at them the wrap will cause rust.. even if they live in the mohave desert).

 

[OrangeCrush496]

Here's a couple pics of my engine compartment. Hopefully it shows enough to answer the questions.

 

[OrangeCrush496]

Sorry they're blurry, my iphone camera has problems

 

[OrangeCrush496]

We need pics of you engine compartment, so we can see your setup. I run several 40's with 350's. They run cool. Do you have an electric fan or a mechanical fan attached to the engine? There's no need to add louvers.

Its an electric fan.

 

[OrangeCrush496]

Does it have headers, or chevy oem cast manifolds? Headers infamously increase the under hood temps. Many wrap them with exhaust insulation when they do (while others “yell” at them the wrap will cause rust.. even if they live in the mohave desert).

It has headers and I've wrapped them with insulation.

 

[OrangeCrush496]

I have a 2001 6.0 LS and use the stock radiator, mech fan, slighty modified stock shroud, cools well, runs 190, hits 200 while trail crawling, maybe 210 id its 100+ and low, low for hours. My 40 has stock inner fenders, I plated the gap from removal of steering box. The exhaust is stock gm manifolds and its wrapped about 30 inches until it gets to collector. Your exhaust is probably close to your slave. a heat shield and sleeve the hose with heat sleeve will help that & iI did a tin heat shield off the rib on firewall to keep radiant heat off master cyls & booster, with the stock louvers in that corner it seems to do well as I only experience a bit of steering fade after hard rocks all day.

Thats a good idea about the slave...it is indeed right near the headers. I wrapped the starter motor with a heat shield [dont judge me for the sloppy installation] which maybe has helped with starting while hot. I'll get some more and wrap the slave and its hose.

 

[Rodger1957]

I had a 350 in an FJ60, it never ran hot. I’d check the radiator with a thermometer to see if there’s any areas that aren’t transferring heat.

I used cast iron exhaust manifolds, and had no issue with overheating the starter.

I also used a flex fan, but I don’t remember if I used a shroud or not.

 

[pb4ugo]

I'm not a fan of electric fans. I've never seen one pull enuff air thru the rad. You can tell the po has had problems with heat. He's insulated the fuel lines probably because the lines would vapor lock. Personally I would install a conventional mechanical fan and fabricate a proper fan shroud. Hard starting could be heat related or something else. Make sure the connection are clean. What's the timing set at? It could be to advanced.
How's it run? Is the engine stock or has it been built up?

 

[peesalot]

IMO the starter is fine and that may actually increase temps, just my opinion. My exhaust is alot tighter around starter and no issues. I would make some alum or plastic plates to rivet on the fan to complete the shroud, close those corners. I would make a tin or alum heat shield to slide in above header tubes and below master cyl's. , let the header heat out the side louver and the hood louver for the master cyl area vent. IMO closing the corners on the back side of radiator will do wonders but with headers its a process of finding what will keep it cool if anything.

 

[3_puppies]

is the engine running hot? or overheating? have you checked with a temp gun
wondering if it is an engine tune issue causing excess heat

there are enough 350's in 40 series out there, for the most part this isn't an issue

 

[OrangeCrush496]

I had a 350 in an FJ60, it never ran hot. I’d check the radiator with a thermometer to see if there’s any areas that aren’t transferring heat.

I used cast iron exhaust manifolds, and had no issue with overheating the starter.

I also used a flex fan, but I don’t remember if I used a shroud or not.

Using the thermometer...How would I tell if there are areas that arent transferring heat? And what does it mean if there are? Sorry...I'm a nooob.

 

[OrangeCrush496]

is the engine running hot? or overheating? have you checked with a temp gun
wondering if it is an engine tune issue causing excess heat

there are enough 350's in 40 series out there, for the most part this isn't an issue

I dont think its overheating....I've only been driving when its cooler outside, since the issues appear when the temperture guauge gets to 170...it got to 200 last summer and the clutch problem was pretty bad. That's based on the guage tho...havent used a temp gun.

 

[pb4ugo]

170 to 200 isn't hot. My 1st 40 runs around 160-170 normally and on long climbs it'll get close to 200. It has a 160 tstat.
I made a fan shroud and properly positioned the straight steel fan 1/2 way into the shroud as is should be. I ran fenderwell headers for decades b4 going to ramshorns manifolds. At the beginning I had cooling problems with a high hp 350, then adapted a shroud which helped a lot. Now the engine is more stk and runs cool.

You might try adding aluminum or metal sheet metal to the open corners so the electric fan can pull air from those areas/corners, like @peesalot mentioned. The metal needs to be spaced away from radiators core, so the fan can pull air. At 1st you could cut and tape cardboard there and see if it helps. Does it have a heater, is there a reason it's not hooked up? I not 100% convinced the heat is effecting the clutch, the headers are above the slave. Below is also the fsm instructions on clutch adjustment. Pedal height, pedal play, rod adjustment. Pedal play is when the slave rod start to move and slight Pedal travel.

 

[Pighead]

it takes too long for the brake pedal to return to "home" and for the brake lights to turn off.

Do you have the return spring on your pedal?

 

[JMZ400]

How old is the brake and clutch fluid? If it's old and contaminated with water, it's possible it's getting hotter than clean fluid.