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1990 silverado 3500 runs hot


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sunear
New User

Apr 26, 2010, 9:55 PM

Post #1 of 9 (2421 views)
1990 silverado 3500 runs hot Sign In

1990 chevy silverado 7.4 runs hot especially when climbing grades have had the clutch fan replaced, thermostat all coolant shroud is in good shape. I am buying a dump trailer and need to remedy the situation. the cooler winter temps seem to help but the hot summer in chico, ca is coming took it to a radiator and a/c guy that has been around awhile truck has 141,000 miles no transmission cooler help?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 27, 2010, 7:39 AM

Post #2 of 9 (2414 views)
Re: 1990 silverado 3500 runs hot Sign In

Not sure what the question is?

Seems like you need a new heavy duty radiator and (you didn't say) if an automatic an additional transmission fluid cooler would be good to preserve the trans. Std trans doesn't generally use a separate cooler if it's a standard shift,

T



sunear
New User

Apr 27, 2010, 8:31 AM

Post #3 of 9 (2411 views)
Re: 1990 silverado 3500 runs hot Sign In

It is an automatic transmission and the radiator shop said the radiator was fine even though it was the original. I have had this truck for 2 1/2 years and it ran hot from the begginning. After I replaced the clutch fan and thermostat and flushed the radiator it helped but when I run up a grade it warms way up to the redline on the gauge and I can smell it is getting hot. No leaks anywhere. As far as power this 7.4 is strong and runs good could haul anything if it would not get warm. Just passed smog with no problems so the engine is running right. Could it need a new radiator? I do not know what else to look for. thanks


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 27, 2010, 12:09 PM

Post #4 of 9 (2406 views)
Re: 1990 silverado 3500 runs hot Sign In

OK: Trying to read between lines of just what is in need and there is need. The original cooling system may not have been enough for this truck and the use it would see. The temp gauge really shouldn't move from the set spot it finds once fully warmed up. You can forgive it for wild extremes of high outdoor temps, or extreme loads, mountain driving and in the rare cases could run heater, slow down, choose a lower gear for the short while it's taxed out.

This likely would have had options for extreme cooling which would have as much as double the radiator - back then more rows of fins, a trans and engine oil cooler AND there are fan clutches for high demand cooling too. Gas mileage is out the window as it's a work truck.

Other ideas and reasons for the temp fluctuations: Could be impellers of water pump just aren't enough or have corroded some. A maybe is that this engine has the wrong water pump as some engines are made for counter rotation. Would take some help to determine if a wrong water pump managed to get installed even if it happened when new!

Check (use care please) that the air blowing off of the fan when fully warmed up is warm air and with aggressive force. If not and engine is hot, radiator is hot then fan clutch isn't doing enough for whatever reason. If you don't have A/C and it never did the first thing thru the grille is the radiator. You can feel the coolant hot from top hose gradually get cooler as it passes thru on to lower hose. You may find a whole section that's cool indicating a problem. If it has or had A/C (don't care if it works - just the parts that would be there) you could feel from the fan side/engine side but would no doubt have to shut engine off as not room with fan moving for a hand to check radiator temps.

If memory serves me - you could get radiators with as many as 4 rows of fins for a full size truck even some large cars a bit older than this for incredible cooling power. The truck body will accommodate more cooling capacity then I think it has now. Radiator specialty shops can put a larger more efficient 'core' in the original end tanks or get a whole one if needed. I see no reason why you can't get this to run at a steady temp (don't play with lowering thermostat's temp rating - use OE suggested one for temp and if possible there's a RoberShaw type that is more efficient which was standard fare when this block was used for marine applications. They plain are better and I'll try to find a picture) in all but the worst extremes.

A side worry: If this has had extended time without use of antifreeze or anti-corrosive coolant where it's used the water jackets may be rusting up and water flow a problem. Would see that just looking in radiator as dirty coolant that about never flushes out to clean looking.

One more: Antifreeze (Ethylene Glycol) can be reduced to a freeze protection level of about -20 or so and will be more effective as a coolant but less anti-corrosive so would change it out more often. Strong mixes - those reading more than the industry standard of -34F which is a 50/50 mix drastically lose heat transfer ability. In other words - stronger antifreeze concentrations can cause overheating!

I'll go looking for a picture of the thermostat and post that separately if I can find it that is great for extreme use conditions. Always use a thermostat as without one at all is not an option and will cause problems,

T



Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 27, 2010, 12:29 PM

Post #5 of 9 (2404 views)
Re: 1990 silverado 3500 runs hot Sign In

Thermostat types for extreme conditions and a regular one....



The above is sold by Prestone now once known as the "RobertShaw" style
of thermostat. You still choose its temperature rating for the application
which would normally be 195F for most vehicles. This style will respond
faster and clear itself of debris better than the more common and still
serviceable "Wax Pellet" style I'll call it that commonly looks like the
one below.



Nothing wrong with this style but when a choice is available I would choose the
other style for a GM large or small block iron engine - a mainstay work horse block
for decades.

NAPA auto parts or a Marine parts outlet may be able to assist in finding the
correct one and temp rating for application,

T



sunear
New User

Apr 27, 2010, 1:10 PM

Post #6 of 9 (2401 views)
Re: 1990 silverado 3500 runs hot Sign In

 


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Apr 27, 2010, 1:24 PM

Post #7 of 9 (2397 views)
Re: 1990 silverado 3500 runs hot Sign In

Nothing showed on your post. Look to right for the word "reply" and when done with text scroll if needed and look for the green box that says "post reply"

I see you are new today,

T



sunear
New User

Apr 27, 2010, 1:24 PM

Post #8 of 9 (2395 views)
Re: 1990 silverado 3500 runs hot Sign In

Tom all great advice! I will start going through the steps and keep you posted as to what is working. I love this truck as it has the power to haul just about anything. The gas mileage is not an issue as I use it for business.The coolant has always looked good and clean. I am aware there should be no fluctuation because I have a 94 2500 also and it runs midway and stays even when loaded down to the max and that with a 305.
Thanks for the advice Bob


Sidom
Veteran / Moderator
Sidom profile image

Apr 27, 2010, 7:43 PM

Post #9 of 9 (2386 views)
Re: 1990 silverado 3500 runs hot Sign In

I pretty much have the same advise as Tom.....

Going off you're 1st post, the 1st thing that popped into my mind was the radiator starting to restrict. Those are classic signs.... Starting to run warm under load & high speeds but there are also other things that could cause this that Tom covered....

Personally since you are planning on doing some heavy hauling with this I would take one of Tom's suggestion and see if there is a HD radiator available for this truck. I'm in the Central Valley as well and I know you'll need it... It also wouldn't hurt to add an addition trans cooler while your at it... This is something that should be done to prevent problems from popping up down the road in the summer...... If it solves your warm running problem as well then that's even better.......






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