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ianacole
05-22-2012, 11:20 AM
This issue just began a couple of months ago. Drove it all last summer with no issues, and in the winter I was worried that I wasn't getting enough heat into it. No changes other than the number of miles on it, but as of a month and half ago the heat started climbing. In a 30 minute drive home or to work it starts pushing 210 degrees. Radiator is hot top and bottom. No leaks. Truck is running just as it did last year - decent power, no backfires, no lugging, no more smoke than there has been previously, it's just overheating now. Need some advice on next steps.

Setup:

73 FJ40
75ish SBC, Carb'd
Stock sized radiator, 4-core, no shroud
160 degree thermostat


What I've done:

Swapped the water pump (minor drip around impeller shaft)
When I swapped the water pump I checked the radiator for sediment buildup - looked clean
Put in a new thermostat (used same 160 degree)
Removed siezed fan clutch and put in new fan clutch
Replaced spark plugs - cylinder 1 looked ugly, a lot of gray ash buildup, the rest looked fine
Checked timing - looks okay
Turned up the fuel mix screw on the carb to run a little richer
Pulled the York compressor to minimize drag/parasitic loss
Checked hoses, don't seem to be collapsing
Replaced radiator cap
Replaced oil pump - doubled the oil pressure, but seems to have accelerated heat-up
Flushed and refilled with 50/50 antifreeze/water mixture

What's left to do, other than replace the motor? Could it be water channels plugging up? I could go to an aluminum radiator and/or a shroud, but this wasn't necessary last year. Am I missing something?

Anyone want to buy a truck? :rant:

Thanks all!

Ian

SteveH
05-22-2012, 12:51 PM
The standard Mud answer (and many other sources) is to fab a shroud for it. Over the years, the most vexing cases I have heard of were solved with a decent shroud.

You don't mention if it's overheating on the freeway, but if it's in town, I'd check the fan clutch performance under various heat conditions. If it does not overheat at 60 mph, then this points to a fan or shroud issues, as at 60 mph, the wind is doing the cooling. Just my .02 - others may see it differently.

rover67
05-22-2012, 01:07 PM
I agree that if you don't have a shroud for it you should make one. it really helps a lot. That is assuming your fan clutch is healthy.

Also, when you make the fan shroud, think about airflow through the radiator. Too many times I see people bolt a flat piece of metal to the back of the radiator, cut a hole in it for the fan, weld a ring on and call it good. The air needs to be able to flow through the radiator, out the back, then get channeled to the middle where the fan ins in some sort of nice gentle fashion.

ianacole
05-22-2012, 01:32 PM
Thanks Steve and Marco. I won't make the truck do 60, but the heat continues to rise
at 55mph. Original fan clutch was seized so I replaced it when I did the water pump about 3 weeks ago.

I've seen mention of using a Taurus shroud, or converting to electric fans. What perplexes me is that it didn't have issues last year.

Corbet
05-22-2012, 04:22 PM
If you have not changed anything do you have an air bubble in the system from sitting? I never ran a fan shroud on my 40. Never had any overheating issues until the engine caught fire:eek: But that's another story. 400hp stroked 383 by the way in SLC and Moab heat. Clutch fan, stock radiator, high volume water pump. Nothing fancy.

Don't get me wrong a should is a good thing. I just did not have the means at that time.

ianacole
05-22-2012, 08:14 PM
I drive it daily...It's gotten worse over the last month or so. What temps were you normally running, prior to the fire, on your 383? Is 210 on a SBC a reasonable temp?

rockrod
05-22-2012, 08:56 PM
have you done a pressure test on the cooling system to check head gasket integrity? not that this is a common issue with a SBC, but it might be worth a look.

Also, why a 160 t-stat? those are for race motors. you should be running at least a 185. I like the 'balanced' t-stats from robertshaw or milodon.

ianacole
05-22-2012, 09:05 PM
I have not, and that's a good idea. The 160 is what was in it, so I just replaced it with like components.

Red_Chili
05-22-2012, 10:53 PM
+1 on a higher temp thermostat. It is counter-intuitive, but really, a hotter tstat makes for a cooler motor.

Doubted, tested, then proven correct on a Honda XR650R hot blooded waterpumping beast. The theory behind it is, it allows more dissipation due to a higher temperature differential in the radiator. It really works. Eliminating the tstat actually made the motor run hotter... less dwell time and temperature differential.

So does Redline Water Wetter. Eliminates bubbles and increases surface contact for heat transfer.

ianacole
05-22-2012, 11:03 PM
Interesting. I up for changing out the thermostat. It looks like my options are 180 and 195 degree units. Which one would be better?

rover67
05-22-2012, 11:13 PM
I'd personally choose a 180.

have you had to add any coolant to it at all over the past year or so?

What are you using to measure temp?

ianacole
05-23-2012, 07:24 AM
Yes, I had a leak around the water pump, and before replacing the radiator cap fluid would vent from there (what a mess) when the engine got hot.

I'll try the 180 this weekend.

Corbet
05-23-2012, 07:35 AM
I drive it daily...It's gotten worse over the last month or so. What temps were you normally running, prior to the fire, on your 383? Is 210 on a SBC a reasonable temp?

Its been a while but I don't recall anything over 200*. 210* is not that hot for a SBC. I was running a 195* and forgot to comment on your 160* Definitely change that out. I had a fancy pants liquid filled mechanical auto meter gauge with its sending unit mounted into the thermostat housing. So I knew exactly when the thermostat opened and closed. The OEM temp gauge had its sending unit in the side of the block. So I had two measurements of temp.

I drove that thing hard as I was still pretty young and dumb. Never had overheat issues.

SteveH
05-23-2012, 11:18 AM
I run a 195* t-stat in my '83 GMC plow truck, but it mostly operates in the winter. I installed a t-stat housing temp gauge (mechanical) and found that Autozone sells a cast-iron (China-mfg) t-stat housing that has 'extra' ports on it - perfect for adding a sending unit. This part was super cheap - $12 or something.

I think 210* is ok - but I wouldn't go lot hotter. By running it hot, at least you burn off any condensate in the motor oil, which was my goal on the plow truck.

rockrod
05-23-2012, 01:20 PM
I run the stock 195 in my 5.3l powered 80 and it runs - 195 to 197 with brief spikes to 200 sitting at a stop light.

get rid of the 160 t-stat. and report back.

ianacole
05-23-2012, 03:51 PM
Thanks. The T-stat is on the schedule for this weekend. I'll let you all know how it goes.

I didn't answer this earlier question: I'm using an autometer gauge.

ianacole
05-26-2012, 06:45 PM
We looked up the OE turdmostat for a '75 C10 Y-code SBC, and it was the 195 degree unit. Replaced it today and went for a ride, and no change. Still climbing up to 210 and hovering there (I haven't wanted to push it to see if it will go further).

So, options? Get the radiator "cored" (is that the right term) and see if it needs a good cleaning? Replace the radiator? Or look at the block?

Corbet
05-26-2012, 07:01 PM
Are you sure your getting all of the air out of the system?

Time to build a shroud.

ianacole
05-26-2012, 07:21 PM
Yes, I believe so. I will tackle that next, but I still don't get why I didn't need one last year.

Corbet
05-26-2012, 08:27 PM
Me either but you changed a lot of stuff most notably the water pump and fan. Good, same, or worse they are different. I'd build a shroud you should have one anyway. ANd make sure you get all the air of the system. I recommend this. It works every time. http://www.summitracing.com/parts/LIL-24610

ianacole
05-26-2012, 08:51 PM
True on the changes, but those came after the heating problems. I will make (or try to find a Taurus) shroud. Thanks for the link...that looks quite handy.

Corbet
05-26-2012, 09:03 PM
The funnel kit is great. You fill the funnel up half full and run the vehicle until the thermostat opens and work out all the bubbles. When done stick the plunger thing in and remove the funnel from the radiator without a mess. Install your cap and done. The extra coolant still in the funnel drains into a coolant jug again no mess. I got mine many years ago for the wife's Subie as they suck to burp. But now I use it on everything as its just so easy and fool proof.

ianacole
05-26-2012, 09:06 PM
Thanks again. Just ordered it from Summit (odd that they weren't the most expensive) ... should be here between June 1-4.

Air Randy
05-29-2012, 08:29 AM
Trying to think of what could have changed since last year to now make it run hotter:

Have you pressure checked the entire system, especially the radiator cap or just replaced it?

Any significant changes in engine timing or carb adjustments? An over-lean fuel or too far advanced timing can contribute to higher engine temps.

You sure when you swapped the T-stat the first time that you didn't put it in backwards?

Based on your comment about the oil pump (although very unlikely) if you are concerned something is going on inside the engine causing it to get hotter, install an oil temperature gauge. If your oil temp is climbing outside of normal range during normal driving then you'll know thats what is causing your water temp issue.

Summit offers a good variety of aluminum fan shrouds for fairly resonable prices.

rover67
05-29-2012, 08:58 AM
Randy has some good points.. Check the timing even if you didn't adjust it, it may have moved..

ianacole
08-19-2012, 07:09 PM
Bringing this back up because I still haven't found a solution. Things I've done since bringing this up. Installed new radiator with homemade shroud (see image). Installed a high volume pump (130-1270P) with all new hoses. Checked the timing (pulling vacuum), and it's spot on, and double-checked the spark plug wire connections. Replaced all the spark plugs. Fill and bleed using the handy Lisle kit. Checked that all spark plug wires are conducting good.

Symptoms:

Overheats under load - Highway speed (55 MPH), or climbing up a hill (like Kipling from Morrison to Jewell). I cannot make the ride home (40 min. drive) that's a combination of surface streets and 285 without breaching 210*. It will recover if I can cruise at ~1500 RPM or downhill.
Water is disappearing - Not into the oil or onto the ground...some of it is undoubtedly from overflowing the overflow tank when overheating, but I suspect some is out the tailpipe.


Does the fact that it's overheating under load point to the timing not advancing enough? Or another problem with the HEI distributor? I have not pressure tested the system, would it make sense to do so now? How about a full flush? I'm tempted to swap out the motor (looking at a Jegs crate motor with a Fuel Injection set up), but I don't want to put a new motor in if I'm just going to jeopardize it with cooling problems.

Any other ideas?

Thanks all!

Corbet
08-19-2012, 07:45 PM
Do a leak down test in insure a healthy head gasket.

What temp thermostat is in it now? And is the rad cap good/new? Also forget the history on that fan clutch?

ianacole
08-19-2012, 07:54 PM
Any suggestions on where to take it to do a leak down?

I'm back to the 2nd 160* Tstat. No difference from when it had the previous 160, or the subsequent 195. Brand new fan clutch and radiator cap.

waggoner5
08-19-2012, 08:08 PM
Yes...pressure test the cooling system. If water is disappearing, this should show where its going. Yes, do a leak down. Most reputable shops will do one for you. Its not a cheap test though as it takes an hour or 2 depending on the guy doing it. Did you use a degree timing light and set the timing for total advance, or just set timing at idle?

ianacole
08-19-2012, 09:34 PM
Timing at idle only...

Corbet
08-19-2012, 09:59 PM
I'd loan you my leak down tester if I was local. You could probably get one from Summit for less than paying for a test. Same with the pressure tester on the cooling system. But I agree with Gary. If your loosing coolant you need to determine where its going.

waggoner5
08-20-2012, 07:45 AM
Timing at idle only...

Timing at idle only only gives you an initial timing. You have no idea where your total timing including advance really is under load. Although I dont think the timing is the culprit here, it certainly can aggravate an existing cooling problem. After doing a leak down, buy or borrow a dial style timing light and check your total advance. A mild SBC likes between 30-34 degrees total advance. Your coolant loss sounds like the big issue though...

Uncle Ben
08-20-2012, 07:54 AM
You state it is a SBC. Is it a 350 or 400 ci?

ianacole
08-20-2012, 08:48 AM
It's a 350, "Y" code, from a 75ish G20 Van, as best I can figure out. Next payday I'll get a leak down test. I can do a compression test (I have a tester) in the mean time.

Uncle Ben
08-20-2012, 09:06 AM
It's a 350, "Y" code, from a 75ish G20 Van, as best I can figure out. Next payday I'll get a leak down test. I can do a compression test (I have a tester) in the mean time.

How clean was the old coolant? I ask as the older SB's had a tendency to accumulate all the rust and corrosion from poorly maintained cooling systems around the rear cylinders. Once it builds up it restricts or even closes off coolant flow to the heads at the back port. Not saying this is what's going on but if it is it's really hard to get that crap out. I have seen and dealt with this a few times over my past life as a shop slave. It was really bad with the '60's SBC. The 400 ci has Siamese cylinders (they touch each other so no flow between cylinders) and the heads have steam holes to allow flow which can have many restriction issues.

ianacole
08-20-2012, 10:13 AM
How clean was the old coolant? I ask as the older SB's had a tendency to accumulate all the rust and corrosion from poorly maintained cooling systems around the rear cylinders. Once it builds up it restricts or even closes off coolant flow to the heads at the back port. Not saying this is what's going on but if it is it's really hard to get that crap out. I have seen and dealt with this a few times over my past life as a shop slave. It was really bad with the '60's SBC. The 400 ci has Siamese cylinders (they touch each other so no flow between cylinders) and the heads have steam holes to allow flow which can have many restriction issues.

And that's ultimately what I wonder is going on. When I pulled the coolant with the first water pump change when the heating issues started it was pretty nasty ... dark brown/blackish.