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Discussion Starter #1
I have a 98 Sidekick Sport with a J23 motor and am having problems with higher than expected engine temps and temps climbing at idle.

Normal 70 MPH speed temps (shown from an Ultragauge ODB2 scan tool) is in the 204-210 range . The Needle in the center of the temp range.

I've been fighting the higher temps since I put the engine in. Here is my setup.

J23 engine with 85,000 miles. (long block swap keeping J18 intake and exhaust and computer/wiring) (Many have run this setup without issue so it's my specific setup)
OEM thermostat (J18 is same as J23) 180 degrees (tested in hot pan on stove before install, works)
3 Row aluminum Radiator Coolant 50/50 premix prestone. Top hose is hot to touch. bottom hose is cool to touch so I know radiator is cooling (cooling space bigger than V6 motors)
16" Electric fan with aluminum shroud (3000 CFM as rated from MFG but can't confirm airflow rating)
New radiator hoses.
New Water Pump (AC Delco rebuilt)
Confirmed the outside engine hoses that wrap around the engine are in good shape and not obstructed. especially to thermostat.
I've pulled the J pipe from the rear of the engine to the top of the radiator and confirmed no obstructions
I know the plumbing to the heater core is correct with
I've back flushed the heater core (didn't get much rust out, I get decent heat)
Stock Sidekick Sport bumper
2" body lift.

I think I should expect to see 195-200 reliably. I know the engine for emissions is set to operate higher, my 2016 Dodge Ram runs in the 198-204 range so I expect it to be normal)

When I stop for a light the temps will rise to 221-224 and I can confirm the fan is running. (800 rpm sitting in traffic)

If I sit and idle at 800 RPMS more than 3-5 minutes the temps will continue to rise with the fan running.

If I rev the engine to 1800-2000 RPMS while parked with the fans running the temps will level and not rise and maintain the 204-210 range..

I have been over every inch of this engine looking for some reason for the high heat and climbing temps.

It's NOT a head gasket. I lose no coolant, The engine does not overheat or climb while driving. I've used an 'air lift' system to fill the coolant as well as running to burp it.
I'm sure the air is out but can't 100% confirm it.

For a while I did the 'pull the bleeder tab off and enlarge the hole on the thermostat but this resulted in it taking forever for the thermostat to open while on the highway on the 35 mile trip to work)
This is not the way to solve this.

Next up is looking at heater core but I doubt I'l find anything there. I have no idea if its original core. I have had this vehicle for 1 year. 246,000 overall miles, I've put 8K on J23 engine.

I also need to confirm the belt tensioner is good. As I routinely run 13.8 - 14.2 volts while running and around 13v when the fan kicks on I don't think the belt is slipping here.

Any thoughts on where else I should look for coolant flow? as I said If I run the engine at at leat 1800 RPMS all remains cool its at idle 800 RPMS when the temps climb, even with fan running.

I don't know what else to check. as I said.. It isn't a head gasket.
 

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Have you confirmed the engine temp with an IR gun?

The ECU engine temp sensor may be defective, different from the dash gauge..
 

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Discussion Starter #3
Have you confirmed the engine temp with an IR gun?

The ECU engine temp sensor may be defective, different from the dash gauge..
The temp sensor is new, I also tested it with a meter in a pan on the stove before installing and it is within spec of Suzuki FSM so I am confident that it is close to accurate.

I am probably placing too much emphasis on the 'ultragauge' in providing me the driving temps and fixating on them in numeric value as they are within the 195 to 220 range and the temp needle on the dash is backing this up being in the 'middle' of the range I should be accepting of this.

I'm more concerned about the temps rising when stopped at idle speeds of 800 RPMS.. and they will remain stable at 1800 RPMS. I don't get into much stop/go traffic but the fan should come on at say 220 and when it does it should drop the temps back down and then shut off.

It's as if the coolant isn't moving fast enough through the system at idle. If it moves faster then it does get cool.

This is all at 40-50 Degrees farenheight. What will I get at 80-90 degrees farenheight?
 

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Clean the couplers and the pins of the temp sensors one for ECU and one for the gauge. Make sure they get good contact. Even the coupler of OBDII pot.
 

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Discussion Starter #8
Seems the electric fan temp is set to come on at to high a temp.
The fan is set to come on about 210 or so. This shouldn't be too high and the fan shouldn't need to be running at highway speeds.

If the fan comes on at 210 at 800RPM the temp still climbs.. If I run it up to 1800RPM with the fan on then the temp will go back down.

This tells me that the coolant flow through the system isn't what it should be.
 

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The fan is set to come on about 210 or so. This shouldn't be too high and the fan shouldn't need to be running at highway speeds.

If the fan comes on at 210 at 800RPM the temp still climbs.. If I run it up to 1800RPM with the fan on then the temp will go back down.

This tells me that the coolant flow through the system isn't what it should be.
no, that tells me the fans either not shifting enough air, or the radiators not sized correctly, water pumps are designed on these vehicles to push enough water to maintain temps within spec at idle. My GV climbs to about 215 F at idle and 180 when moving. electric fans are all factory so whats different to factory on your one? fan and radiator.
 

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hang on, I just re-read your original post.
AC Delco "rebuilt" pump???? ewwwww would be my first thought, why a rebuilt unit?
is the pump actually shifting water properly or is it cavitating? did they actually fit an OEM impeller? or something generic? I never trust reman pumps, ever.
 

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Discussion Starter #12
no, that tells me the fans either not shifting enough air, or the radiators not sized correctly, water pumps are designed on these vehicles to push enough water to maintain temps within spec at idle. My GV climbs to about 215 F at idle and 180 when moving. electric fans are all factory so whats different to factory on your one? fan and radiator.
The original radiator was a 1 row 1/2 inch core, I put in a 2 row 1 inch core radiator for a GV 2.5 and then moved to a 3 row aftermarket aluminum. It should be more than enough to cool in this situation. The one on the left is the 2 row.

95651


The fan has a shroud I made out of a baking pan and the fan is rated at 3000 CFM (but I don't have a way to measure this)

95652


I don't think I have underspec'd this. the fan controller is adjustable and I have tried having the fan come on earlier too.

I have bought reman water pumps for the last 40 years without much issue. While I have seen where different impeller designs being used. I compared the impeller with the one I took off and it was the same design. The only difference I could see is the impeller blades were about 1/4 inch longer. I have in the past seen impellers 'spin on the shaft' so I decided to get another pump while I took it apart to check. I did not look at the one I took off for 'genuine suzuki marks' I decided to replace it as I had already purchased it.

When I put in the OEM thermostat I compared it with the Stant one I replaced. The 'hole' when opened is larger for the OEM.

I have an IR thermometer and will check temps.
 

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An idea comes up. Can you replace all small cooling system hoses, except the two larger rad hoses.
 

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Discussion Starter #14
An idea comes up. Can you replace all small cooling system hoses, except the two larger rad hoses.
I have pulled and inspected all these hoses as well for obstruction. They are good.

The only thing I have not inspected or replaced fully is the heater core. Because some coolant flows out the back fo the head through the heater core and into the water pump housing (to aid in opening thermostat) I do wonder if it may not be flowing well enough and causing some additional heat.

I want to get ahold of a heat camera and get photos of the radiator and engine and cooling tubes as well as get some IR readings.

I don't get much time during the week to mess with it so this is more of a weekend investigation, I do want to drive it during the week to work but not until I figure this out.
 

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Make sure the pipe #22 and hose # 18 are not clogged with rusty debris!! I have already replaced the hose # 18 two times due to their curved shape.
 

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