Overheating/coolant loss on long trips

btwilson86 · 04-15-2011, 11:08 PM

The temp gauge fluctuating and the heater changing from hot to cold sounds like you have air in the cooling system (which makes sense if it's been purging coolant).

After it overheats, is there any hot or cold spots in the cooling system? For example, is the upper hose hotter than the lower hose? One side of the radiator hotter than the other?

A possibility is that there may be some sort of blockage restricting the flow of coolant, causing it to overheat

dannydavi · 04-15-2011, 11:31 PM

Quote:

Originally Posted by btwilson86

After it overheats, is there any hot or cold spots in the cooling system? For example, is the upper hose hotter than the lower hose? One side of the radiator hotter than the other?

A possibility is that there may be some sort of blockage restricting the flow of coolant, causing it to overheat

I will hand check multiple places next time it occurs, I don't have a temp gauge that I can use to test it. Also I will try to see if the rad is blocked up at all... Any good ways to test that? I will try taking both hoses off of rad and full pressure garden hosing in the top and see if it backs up at all...

87hilux7mge · 04-16-2011, 08:37 AM

if the rad is original, might be a good idea to look for a new one. to purge the system of air, put the front of the car on jack stands, high as you can get em safely. then take the cap off the rad, and start the car. make sure the coolant is circulating, and while it is doing so, top off the rad. it may take a few mins as the car will warm up and open the thermostat. to help the process along, squeeze the lower and upper rad hoses and heater hoses periodically.

another thing you can do it replace your thermostat. if its a stock on, get a new one, as it may be malfunctioning. also check if you fan is working properly, you could have a slipping clutch. this would not attribute to you losing coolant, but might have to do with your temp fluctuations.

cre · 04-19-2011, 05:15 AM

You are aware that 200+psi is WAYYY too high.... right? The N/A is supposed to be mid 150's.

87hilux7mge · 04-19-2011, 07:00 AM

cre, ive been curious about this too. the two motors i picked up for my project (88 jdm 7mge, 90 cressida 7mge) both tested high compression while cold! the jdm motor ranged 185-193, the cressida ranged 20-195 (3 cyls were completely boned). when i disassembled the motors, they both had the same type of pistons, but when i compared them to my new pistons, they had considerably less dish in them, almost flat tops. i was concerned that id gotten turbo pistons, but compared them with my freind john's pistons, and mine were definitely for N/A. so somewhere, toyota got a wild hair up their bum and put high compression n/a pistons in some motors.

i had no luck finding these pistons anywhere.. but that seems to be in the same compression range as mine, since his was warm.

sorry that was a lil off topic...

cre · 04-20-2011, 04:11 PM

I'm going to hazard a guess that no one's bothered to get the part number and manufacturer off of one of these? It's cast inside.

Have either of you measured the dish volume?

87hilux7mge · 04-20-2011, 07:27 PM

i did a ruff measure and the flat top is almost 1/16th deep, not counting valve relief. my new pistons are 1/8th. i cant recall what the dish is on turbo pistons.

i can get the part # this weekend and post it up sometime next week. im ashamed to say, i never thought to get the number and cross reference it from the factory...fail.

i will certainly check it out though!

dannydavi · 04-22-2011, 08:11 PM

Quote:

Originally Posted by 87hilux7mge

cre, ive been curious about this too. the two motors i picked up for my project (88 jdm 7mge, 90 cressida 7mge) both tested high compression while cold! the jdm motor ranged 185-193, the cressida ranged 20-195 (3 cyls were completely boned). when i disassembled the motors, they both had the same type of pistons, but when i compared them to my new pistons, they had considerably less dish in them, almost flat tops. i was concerned that id gotten turbo pistons, but compared them with my freind john's pistons, and mine were definitely for N/A. so somewhere, toyota got a wild hair up their bum and put high compression n/a pistons in some motors.

i had no luck finding these pistons anywhere.. but that seems to be in the same compression range as mine, since his was warm.

sorry that was a lil off topic...

I took out the thermostat to make sure it wasn't that. The rad was replaced a little over a year ago, although I haven't ruled that out yet. The fan clutch I replaced this weekend because the checks I did on mine seemed like I should replace it... but still overheating

When I took the rad off I flushed it best I could and it seemed to be flowing just fine. Also felt the upper and lower hoses and noticed the bottom was cooler than the top, but still warm.

after looking more into it, it seems on long trips is only time it occurs, around town I'm golden.

cre · 04-22-2011, 08:27 PM

Stock dish is 3mm below the crown. I don't know what's up if you've actually got different pistons; Usually the high readings are the result of oil draining into the cylinders from the plug galley.

Danny, what's your timing set to? Retarded timing (both mechanical and ignition) will cause higher engine temps.

dannydavi · 04-22-2011, 08:33 PM

Quote:

Originally Posted by cre

You are aware that 200+psi is WAYYY too high.... right? The N/A is supposed to be mid 150's.

I thought it was supposed to be 185ish... what does it mean if the compression is higher than it's supposed to be?

04-15-2011, 11:08 PM	#1
btwilson86 Super Moderator Join Date: May 2007 Location: Billings, Montana Posts: 1,034	The temp gauge fluctuating and the heater changing from hot to cold sounds like you have air in the cooling system (which makes sense if it's been purging coolant). After it overheats, is there any hot or cold spots in the cooling system? For example, is the upper hose hotter than the lower hose? One side of the radiator hotter than the other? A possibility is that there may be some sort of blockage restricting the flow of coolant, causing it to overheat __________________ 1989 7MGTE R154 Targa Top White Package w/Blue Interior Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels

04-16-2011, 08:37 AM	#3
87hilux7mge walbro fp Join Date: Dec 2010 Location: spokane Posts: 479	if the rad is original, might be a good idea to look for a new one. to purge the system of air, put the front of the car on jack stands, high as you can get em safely. then take the cap off the rad, and start the car. make sure the coolant is circulating, and while it is doing so, top off the rad. it may take a few mins as the car will warm up and open the thermostat. to help the process along, squeeze the lower and upper rad hoses and heater hoses periodically. another thing you can do it replace your thermostat. if its a stock on, get a new one, as it may be malfunctioning. also check if you fan is working properly, you could have a slipping clutch. this would not attribute to you losing coolant, but might have to do with your temp fluctuations. __________________ 87 toyota 4x4 single cab short box pickup, 7MGZE.

04-19-2011, 05:15 AM	#4
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	You are aware that 200+psi is WAYYY too high.... right? The N/A is supposed to be mid 150's. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

04-19-2011, 07:00 AM	#5
87hilux7mge walbro fp Join Date: Dec 2010 Location: spokane Posts: 479	cre, ive been curious about this too. the two motors i picked up for my project (88 jdm 7mge, 90 cressida 7mge) both tested high compression while cold! the jdm motor ranged 185-193, the cressida ranged 20-195 (3 cyls were completely boned). when i disassembled the motors, they both had the same type of pistons, but when i compared them to my new pistons, they had considerably less dish in them, almost flat tops. i was concerned that id gotten turbo pistons, but compared them with my freind john's pistons, and mine were definitely for N/A. so somewhere, toyota got a wild hair up their bum and put high compression n/a pistons in some motors. i had no luck finding these pistons anywhere.. but that seems to be in the same compression range as mine, since his was warm. sorry that was a lil off topic... __________________ 87 toyota 4x4 single cab short box pickup, 7MGZE.

04-20-2011, 04:11 PM	#6
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	I'm going to hazard a guess that no one's bothered to get the part number and manufacturer off of one of these? It's cast inside. Have either of you measured the dish volume? __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

04-20-2011, 07:27 PM	#7
87hilux7mge walbro fp Join Date: Dec 2010 Location: spokane Posts: 479	i did a ruff measure and the flat top is almost 1/16th deep, not counting valve relief. my new pistons are 1/8th. i cant recall what the dish is on turbo pistons. i can get the part # this weekend and post it up sometime next week. im ashamed to say, i never thought to get the number and cross reference it from the factory...fail. i will certainly check it out though! __________________ 87 toyota 4x4 single cab short box pickup, 7MGZE.

04-22-2011, 08:27 PM	#9
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Stock dish is 3mm below the crown. I don't know what's up if you've actually got different pistons; Usually the high readings are the result of oil draining into the cylinders from the plug galley. Danny, what's your timing set to? Retarded timing (both mechanical and ignition) will cause higher engine temps. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

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