4.3 Jimmy Rooftop w/malone Autoloaders

While hauling our 2, 13 foot necky’s on

rooftop with Malone Autoloaders. Noticed the

engine over heating at interstate speeds

then just holding at the redline at 55 mph.

Is this normal or do I have some issues to look for

with my cooling system? This happened on our

last 2 outings.

yeah it sounds like something is wrong
how many miles are on the Jimmy? It could be getting tired.

Check coolant levels, make sure there is nothing blocking the radiator. Maybe replace the thermostat too. They are cheap and easy to replace.

One thing that may help, though it could be unpleasant during the summer is to crank the heater up to help dissapate heat better. Roll down the windows so you don’t roast in there.

Possibly head gasket time

– Last Updated: Jun-19-10 7:30 AM EST –

Gotta love GM.


check coolant sytem …

– Last Updated: Jun-19-10 10:28 AM EST –

....... it's not the kayaks .

If you need help in how to , ask .

I should be more clear . There "is" a problem with your coolant system . Autos do not go into the red , overheat unless there is a problem .

Take it to a mechanic
A couple kayaks on the roof of that vehicle shouldn’t make it overheat.

That said, some vehicles are notorious for having overheating “issues” when the engine is working hard. A section of I-70 called Floyd Hill west of Golden frequently hosts lines of vehicles pulled over in summer, spewing coolant and/or steam. When Chrysler minivans were THE kid-hauler to be seen in, they were always in the line-up, conspicuous in their great majority. Apparently, the radiators were undersized.

I have heard that the 4.3L V6 in the S10/Blazer/Jimmy series was somewhat prone to coolant problems. You may want to surf the Internet to find out more on this.

After the first episode it went into the shop.

The notorious intake manifold gasket was replaced,

oil and filter changed, air filter replaced,

and anti-freeze replace with glycol(green) instead of

the dex-coolant(red stuff). Cooling system was

flushed 3 months ago, new thermostat and pump

then also. This is a 2000 Black Diamond Jimmy

w/107k miles 4wd. Well cared for.4.3 motor.

Thinking maybe Trailering?

Hate to say it but
There’s still something wrong with the truck. I’ve been carrying boats on top of cars for 30 years, and have never seen that happen, even with engines as small as 1.8L that were hauling 2 sea kayaks on the roof and up to 2 weeks worth of camping gear.

When we drove to Newfoundland in 2003, my better half’s 1992 Subie wagon didn’t have enough power to climb steep hills faster than 35 MPH with all the stuff we had in and on it, but it never came close to overheating.

An engine as powerful as a GM 4.3 shouldn’t even notice 2 13 footers on the roof, IMO.

Have YOU looked under the hood?

– Last Updated: Jun-20-10 2:10 PM EST –

Can you smell any AF? Are there stains? When "they" changed the coolant, did they also pressure-test the cooling system? Have YOU checked for loose hose clamps? Does the engine run rough?

Did the overheating begin right after "they" flushed the coolant 3 months ago? If they did a power backflush and the coolant had gone too long a time before that, it's possible that something gave way. I think most, if not all, radiators now are composite but I don't know about what GM used in your vehicle. Maybe a rusty spot became a tiny hole.

I once had a '77 Nova overheat, complete with steam and fluid spewing on the highway. There was a slow leak in the coolant OVERFLOW reservoir and a loose hose clamp. Check yours! That car's engine was the ancestor to what's in your Jimmy, BTW. Someone told me that GM basically lopped off 2 cylinders and didn't do much else to the design.

Trailering is nice; it's what I do for height reasons. But it won't solve your overheating problem, since trailering also imposes a load on the tow rig. (How's your transmission?)

This could be it too

– Last Updated: Jun-20-10 4:31 PM EST –

You may be running too much ignition advance, causing the air/fuel to ignite prematurely.
It can result in severe engine damage if not taken care of.
If your timing is the culprit, it will usually be most likely to rear its head when a load is applied.
Something like going up hills while unloaded might make it detonate, but the cooling system could keep up since it wouldn't be continuous. Once you throw the kayaks on the roof, the load becomes continuous, and the engine cooling system eventually is overloaded. Once it gets hot, the problem becomes even worse, and it snowballs.
So...you may be able to run a higher grade of fuel, like premium to test this. Wait till you are just about empty so it isn't diluting your new fuel, put in premium, and dump in some octane booster to boot.
Load up the boats and see what happens.
You may be able to hear it detonating now with regular fuel, if that is what you are using. While going up a steep hill, or otherwise loading the engine, (once it is warmed up) apply gas pedal firmly to the floor. You may hear a faint knocking, or faint metallic pinging rapidly emanating from beneath the hood. That would be premature detonation, and it is easy to fix, but like I say, if left untreated it will very rapidly destroy your engine.

No, it is not normal.
You have problems.

I haul two kayaks and a canoe at one time on our V-6 and never have had a overheating problem.

It could be as simple as your thermostat

Jack L

I have the same engine in
a 2003 sonoma,never had it overheat. Drove 5 hours last month with 2 kayaks on the roof and 2 on a trailer.

My opinion is that the radiator is starting to plug up. It seems like it will cool great under normal use, but when the load increases it can’t get rid of the extra heat.

IF the thermostat is only opening part way, that may account for it but still leaning toward the rad. However, the thermostat may be the best thing to start with as it is cheap and easy to get at. right on top of the engine. Get the GM one, I find aftermarket units not up to par.

you probably know about the GM Dex

– Last Updated: Jun-21-10 10:45 AM EST –

....... http://blogs.cars.com/kickingtires/2008/03/gm-pays-out-for.html