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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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Or go back to the OEM fan setup!
 

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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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Well I bypassed the heater core. I don't need heat.
 

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Discussion Starter #17
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.
I've pulled apart and checked every coolant hose I can find for obstructions on this motor and temp readings are still around 204 up the highway via an ultragauge at the ODB2 port.

I back flushed the heater core and even ran 'CLR' to remove any scale in the core and got very little rust out.

I filled the coolant with an "air lift' system where i sucked all the air out, collapsed the hoses and put coolant back in. I then ran it with a large funnel and tried to 'burp it' and did get some air out so the air lift didn't allow all the air to be 'sucked out' . (Head gasket is good, I know this for sure)

I've checked for any clogged fins in the radiator and AC condenser and confirmed hose routing. They are good.

Next I'm going to take the front bumper off and take a drive and see if it is an airflow problem as the Sports large bumper is in the middle of the radiator.

I have also located a thermal camera to see if it can help tell me anything more.

I'm missing something here.
 

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Fan should pull enough air that the bumper is not an issue. I'm still going with put a clutch fan on it.
 

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When I did with the pipe #22 and hose # 18, I used a wire tying to a small piece of cloth to pull through them and they came with rust debris. My 96' Sport almost stock except the a little bit tires runs full hot at 212f by the scan tool. At this temp, the AC works great and I bypassed the heater core. I don't need heat! It is more or less to the spec.This engine really runs hot! The only way for you is to go back to OEM rad fan.
 

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212F is well below the 230F boiling point when its under pressure so thats fine.

I still think the radiator and fan are the issue, is the radiator actually sized correctly? if its got larger core tubes then its always possible the pumps not shifting enough water to overcome the surface tension on the tube walls and its just circulating water down the centres and not getting enough heat out. Unlikely but possible. You can fit too big a radiator.
Got the old one lying around? what happens if you toss that and the OEM fan back in?

What is the coldest temp you get to? 50/50 mix may be part of the issue, dilute down to 70/30 and that will help with cooling, the antifreeze is just that, anti freeze, its not a thermally conductive fluid, and too much will make it run hotter for sure. Run a mix suitable for coldest temps you experience and no more. 70/30 is good to about 0F, maybe a bit lower, 50/50 gets you to -25F and a boiling point of about 230F

is the thermostat actually opening at the correct temp? I know others on here that fitted aftermarket 82 degree ones that opened at 85 then stuck, or didn't open fully.
 
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