Hot engine when spinning fast (1 Viewer)

[SHIfTHEAD]

So I've read through many threads on this subject, but I'm trying to determine my course of action with a hot engine, at times. It's hot when the engine is turning over fast on climbs, this I understand, kinda.

It seems that at times when I have to downshift to make an especially steep climb that the engine will still climb upwards of the 220s, per Torque (I have a 1997). This puzzles me as turning over faster, presumably spins the water pump faster and this moves water through the system faster. Another data point: if I crank the heat inside to full blast and set recirc to outside air it will stop the temps climbing for the duration of the climb in almost every case. This implies the issue is purely about cooling area surface, but I've read our radiators (mine is a new Denso and new cap, thermostat, hoses) have more than enough capacity to keep these engines cool.

So I'm left thinking the water pump has lost efficiency...? I can't really draw another conclusion. If it were the fan then why would I have this issue when climbing at 60mph? The engine is also hot when spinning fast at lower speeds, but I feel this can be from various things. Hot when spinning fast and when going fast (50+ mph) should allow me to rule out things, like the fan clutch...I think.

Maybe I'm missing something here, so was hoping someone would turn on the light for me.

 

[Squeegee]

I had a similar issue. For me at least, putting 20k cst fluid in my eaton fan clutch helped a ton

 

[SHIfTHEAD]

I had a similar issue. For me at least, putting 20k cst fluid in my eaton fan clutch helped a ton

I've got some on order, so I'm doing that for sure. Was just curious if anyone experienced water pump performance decline, as that seemed a bit far fetched to me.

 

[gummycarbs]

Have you tested your thermostat to see if it's opening at the right temperature and opening sufficiently?

Have you tested the fan clutch using the newspaper test? i.e. push a rolled-up newspaper against the radiator fan when it's hot to see if there's resistance? You should hear *some* roar of the radiator fan at startup after it's been sitting, too.

Have you done a chemical flush of the cooling system? Were red and green coolants ever mixed?

For what it's worth, I changed my water pump at ~250k miles and it looked and felt pristine. I have no way of knowing if it's original, but I've had a similar experience on other vehicles of a similar mileage, even ones with significant corrosion in the coolant passages of the block and a somewhat clogged radiator.

 

[SHIfTHEAD]

Have you tested your thermostat to see if it's opening at the right temperature and opening sufficiently?

Have you tested the fan clutch using the newspaper test? i.e. push a rolled-up newspaper against the radiator fan when it's hot to see if there's resistance? You should hear *some* roar of the radiator fan at startup after it's been sitting, too.

Have you done a chemical flush of the cooling system? Were red and green coolants ever mixed?

For what it's worth, I changed my water pump at ~250k miles and it looked and felt pristine. I have no way of knowing if it's original, but I've had a similar experience on other vehicles of a similar mileage, even ones with significant corrosion in the coolant passages of the block and a somewhat clogged radiator.

Good points! This truck is fairly new to me, as an owner, but I know the PO well and he did no preventative maintenance. I will do all of these tests, including the thermostat as I've been burned by new parts that don't work properly.

As for the chemical flush of the cooling system, do I need to be worried about dislodging debris and completely blocking head passages? I see no debris when the rad cap is off, so I'm guessing it's pretty clean, but perhaps some passages have build up that can restrict flow.

Thanks for the responses!

 

[gummycarbs]

do I need to be worried about dislodging debris and completely blocking head passages?

I've personally never heard of that happening.

I see no debris when the rad cap is off, so I'm guessing it's pretty clean

That's what I thought when I first saw what turned it to be the most clogged radiator and corroded cooling passages I've ever seen.

Personally, I would be doing several chemical flushes, followed by one or more distilled water flushes, then replace the water pump. Chemical flushes can be hard on water pump seals when debris is dislodged. Not saying it *will* kill your water pump seals, but it could.

Since it's been neglected, just do the whole shebang. Chemical flush, water pump, thermostat, all hoses, and the radiator if it's showing signs of aging.

 

[SHIfTHEAD]

I've personally never heard of that happening.



That's what I thought when I first saw what turned it to be the most clogged radiator and corroded cooling passages I've ever seen.

Personally, I would be doing several chemical flushes, followed by one or more distilled water flushes, then replace the water pump. Chemical flushes can be hard on water pump seals when debris is dislodged. Not saying it *will* kill your water pump seals, but it could.

Since it's been neglected, just do the whole shebang. Chemical flush, water pump, thermostat, all hoses, and the radiator if it's showing signs of aging.

Yeah, this sounds like a good plan of attack. I had planned on doing the water pump anyway since I don't know when/if it's been done yet. I'll do the oil pump seal and front main while I'm there too.

So looking at the various products, Evapo Rust has one called Thermocure. As they are awesome in the rust removal business, this seemed like a good one. But in truth I have no experience here.

Which ones do you all use?

 

[gummycarbs]

Which ones do you all use?

Personally, I used several passes of Prestone flush. I think it's just a low concentration of trisodium citrate. I drove around town for several days on each pass.

I didn't bother with any of the other Prestone flushing doo-dads. I used tap water to force water through the radiator, block, and heaters, but I always followed with a flush cycle of distilled. We don't have hard water here, but I'm not taking any chances.

I hadn't heard of ThermoCure at the time. I know that EvapoRust is good stuff, so I'm sure ThermoCure is, too.

 

[baldilocks]

Sounds like a normal reaction to increased engine load. You get to 220 in which gear at what rpm for how long up what percent grade at what ambient temp?

You’ll be in second gear for a long time in hot temps dragging yourself up out of Death Valley or are you seeing 220 after 1 minute of a 3% grade in 60 degree temps?

 

[Kernal]

IME you can sometimes open up a can of worms (cause leaks) with aggressive cooling system flushes particularly if the previous owner had used any sort of cooling system or head gasket stop leak before you bought the vehicle.

If the system doesn't look rusty, greasy, or full of crud I might focus on the fan clutch and Thermostat and go from there.

Is the cooling system (level) dropping, are you loosing coolant, do you have to top it off now and then??
Are there any external leaks in the cooling system?
Is the radiator overflow tank overflowing itself??
What brand was the new Thermostat?
What brand was the new radiator cap?
What concentration of anti-freeze to (?distilled) water are you using?

FWIW

 

[clx16]

So you can pass coolant through a radiator too fast that it doesn't have enough time to cool. On the old Chevy engines that were put in cars with radiators that had less little space for airflow people would think they were helping by pulling the t-stat out but they would find the engine would run even hotter at faster speeds. This was because the coolant didn't get enough time in the radiator to cool. Not really what we experience on our 80s in general, as with out a t-stat where you are at, it might not ever get up to operating temperature. NOT super relevant information to your situation, however it would lead me to be more focused on the radiator and fan along with t-stat function as it sounds like you may be overwhelming the radiator or being choked by the t-stat at higher RPM. Obviously your fan not keeping up, could lead to the radiator getting overwhelmed. You are sure the radiator fins get clear flow even with your A/C stuff sitting in front of it? no stuff blocking either of them?

however if you do what @gummycarbs says you will get to see if there are a pile up of bugs implanted or not, that need removing. I know for science you should do one thing at a time and try to figure it out.... I rarely do that, I would go full flush and cleaning, and then start replacing the part you know you are going to want to replace anyway as part of a baseline. its nice to have things flushed before you start adding your new stuff anyway.

 

[ceylonfj40nut]

What radiator do you have? Folks including me have had night and day difference using a TYC radiator with >15k fluid in fan clutch.

 

[freshspecbluegt]

Also don’t underestimate belt tension. There is a belt tension spec in the FSM and a click type belt tension gauge is 15 bucks. I use one every time I change or reinstall belts and it is quite surprising how tight the belts actually are set. I know everyone does it but I would be surprised if anyone could really set up the belts per the FSM spec using the thumb method.

 

[leonard_nemoy]

Sounds like a normal reaction to increased engine load.

I'm with you, I know my cooling system is up to par but when I start climbing elevation in 100F + weather I can definitely see temps around 210-220F. This is when I shut down the AC until I am done climbing. It's worse for me when I am gaining elevation off road instead of highway speeds.

 

[SaturnAscends]

I've read somewhere here that even at highway speeds proper operation of the fan clutch is essential to draw cool air in due to the brick-like aerodynamics of these trucks.

 

[baldilocks]

I'm with you, I know my cooling system is up to par but when I start climbing elevation in 100F + weather I can definitely see temps around 210-220F. This is when I shut down the AC until I am done climbing. It's worse for me when I am gaining elevation off road instead of highway speeds.

Heavy oil in the fan clutch and low range off road unless I’m on fairly flat ground.

 

[SaturnAscends]

I've personally never heard of that happening.



That's what I thought when I first saw what turned it to be the most clogged radiator and corroded cooling passages I've ever seen.

Personally, I would be doing several chemical flushes, followed by one or more distilled water flushes, then replace the water pump. Chemical flushes can be hard on water pump seals when debris is dislodged. Not saying it *will* kill your water pump seals, but it could.

Since it's been neglected, just do the whole shebang. Chemical flush, water pump, thermostat, all hoses, and the radiator if it's showing signs of aging.

Would you say there’s a risk of developing a heater core leak with a chemical flush on such an old system?

I just drained the rad via the peacock and also the lower radiator hose and engine block and didn’t see much debris if any, so I just did a drain and fill to avoid having to deal with gallons of waste fluid. No issues so far.

I’d think there would have to be a lot of rust and crud in the system to make the benefits outweighs the risks of a chemical flush, but I could be wrong.

 

[gummycarbs]

Would you say there’s a risk of developing a heater core leak with a chemical flush on such an old system?

If your heater core is so far gone that a mild acid causes a leak, then it was about to start leaking soon regardless.

Personally, I don't view rust and deposits as being structural.

 

[BILT4ME]

Personally, I don't view rust and deposits as being structural.

Unless it's a head gasket.

Fix it until it's broken!

 

[SpenserAK]

Fix it until it's broken!

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