1997 Chevy S-10 10 degree increase under acceleration

Tiny
CRAZNDN
  • MEMBER
  • 1997 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 12,500 MILES
I have a good one. Under acceleration coolant temps rise 10-12 degrees. This never happened in 120,000 miles and came on abruptly. I have replaced-radiator, water pump, thermostat, clutch fan, hoses, catylitic convarter, fuel filter. I isolated the the transmition rad. Cooler with an external unit. Have check maf and O2 sensors cold and hot all with in specs. Checked intake for cracks. To witch I thought it could be, you know maybe a confused computer. It's not using coolant, no bubbles in the rad, no fluid in the oil. It runs good, just wants to heat up. Help!
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Friday, January 22nd, 2010 AT 3:18 PM

16 Replies

Tiny
PEAR69
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Change the coolant temperature sensor (cts).
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Friday, January 22nd, 2010 AT 11:42 PM
Tiny
CRAZNDN
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I guess this is a possibilaty But it only happens when going up a hill when you kick into a lowwer gear. On steady highway speed it does'nt do it, it stays steady. It would seem that if it was the sensor it would do it all the time. I have done external temp monitoring through comp. Port on a drive cycle and it seems to agree with the dash gauge. Please reply.
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Saturday, January 23rd, 2010 AT 8:53 AM
Tiny
PEAR69
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Check the resistance of the CTS, and compair it to the corresponding sensor spec. The CTS and the IAT change resistance as the coolant (cts) or air (iat) heats up and cools.
Also, make sure the A/C condenser is clear of debris. The condenser is in front of the radiator, and debris can block air flow to the radiator.
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Saturday, January 23rd, 2010 AT 10:25 AM
Tiny
CRAZNDN
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I changed (cts) no change in the problem. Cleaned cooler when new rad. Was put in. This problem exists at 5 degrees or 90 degrees, the temp. Change is a constant. What next?
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Sunday, January 24th, 2010 AT 9:53 AM
Tiny
PEAR69
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Did this happen before or after the radiator change? Be sure that there is coolant in the reservoir.
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Sunday, January 24th, 2010 AT 11:42 PM
Tiny
CRAZNDN
  • MEMBER
This happened before all of the repairs listed in my original E-mail. These repairs have all been done in the last 45 days, and none of the repairs did anything to improve the problem. The problem started going up a long grade with a load on the truck. I assumed I had over heated the trans, so a trans cooler was added and fluid and trans sceen changed. Did'nt work. So Iisolated the trans. By just running the fluid through the external cooler bypassing the rad. Cooler. Did'nt work. So then I knew it was a cooling problem and not the trans. So started all the cooling repairs. Did'nt work. Used run mode scanner to check sensors O2 (maf) timing advance, It seemed to act like timing retard. Checked for intake leaks maybe lean condition. I'm stumpped!
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Monday, January 25th, 2010 AT 8:28 AM
Tiny
PEAR69
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Ok, I assume that you have confirmed that coolant is flowing through the engine when the t-stat opens up -- right. So, being that you have changed everything - confirmed that coolant is flowing when t-stat opens -- brings me to this point. Coolant gets hot when the t-stat holds it in the engine until a certain temperature is acheived (usually around 180 degrees or so). Then the t-stat allows the coolant to flow - thus the upper radiator will get hot and it will pressurize. - I am sure you know this -. Now, if the coolant flow is blocked or restricted from flowing through the radiator, then the coolant will absorb too much heat from the engine. I think you may have a restriction in the coolant flow, internally, in the engine. Being that everything is new - (the radiator, water pump, all the hoses) - the only thing left is to flush the engine block out by removing the water pump again, and flushing the block with some presurized water through the water ports on the block. The water should flow out just about at the same pressure as it goes in -- if not -- remove the soft plugs in the block and flush again to find the blockage (if there is one).
Also, try changing the radiator cap -- it may be stuck.

What type of scan tool are you checking the timing with?
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Monday, January 25th, 2010 AT 6:37 PM
Tiny
CRAZNDN
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I do seem to have flow, but I also had a suspition of a partial blockage or maybe sludge build up in the passages, there was alot of heavy orange sludge in the old rad. Is using a heavy duty rad. Flush ok in your opion? I do have a quick flush port on one of the heater hoses. My scanning tool is a Actron model cp9180 it's a fairly decent scanner for a back yarder.
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Monday, January 25th, 2010 AT 7:20 PM
Tiny
PEAR69
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Ah yes -- "orange sludge" rears it's ugly head once again. That is the effect of GMs' version of Dexcool (the orange coolant). Your radiator is new so you shouldn't want any of the sludge that is in the engine to break free and clog the new radiator and /or the water pump - (and it will). To be honest, it is only a matter of time before you need to replace the lower intake manifold gaskets, so I would just go ahead and remove the water pump - flush the crap out of the system with a high pressure hose. Then remove the soft plugs and flush again the same way. Most of the sludge should come out of the soft plug holes - and this will totally flush the entire engine block -- but not the heads. The heads is where this sludge really causes problems - and probably yours. The build up is usually most around the number 7 and 8 cylinders (the back of the engine). The best way to clean up the heads is to remove them -- but you can also just remove the lower intake manifold (which will need to be done soon anyway) and very carefully clean and flush out the heads that way. Then replace the lower intake gaskets (and be sure to use the new, more expensive, style gaskets with the metal inserts to prevent over torqueing).
A radiator flush may or may not do the trick.I know it seems extreme and it is a lot of work, but if the blockage gets worse, it can distort the cylinder bores (from uneven heat dissipation) and cause the head gasket or even the piston rings to fail prematurely. Be sure to put new soft plugs in the block useing gray silicone - and allow at least a day before you put coolant in the engine (this will allow the soft plugs to properly seal). Use Prestone Dexcool coolant - not GM Dexcool. Mix it properly or just buy it premixed.

The scan tool is a good tool for the home mechanic, but it cannot tell you where the timing of the engine is at. It just tells you the spark advance or retard degree from the base timing point. The base timing point (which is +or- 1 degree of TDC) is set by adjusting the distributer and using a GM Tech One scan tool. Timing lights will not work. These scan tools are not usually not available outside of a dealership and they are around $15000.00 bucks. Anyway, I don't think it is a timing issue -- it probably is a blockage in the cooling system caused by GM Dexcool (the orange coolant). BTW - google 'gm dexcool settlement'. You may be suprised.
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Monday, January 25th, 2010 AT 8:16 PM
Tiny
PEAR69
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Flush the block through the water pump ports and soft plugs - as I described - and then remove the lower intake manifold (and the heads if you so desire).
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Monday, January 25th, 2010 AT 8:20 PM
Tiny
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Thanks for the info. I guess? I had thought that might be a possibilty, but tried to put that out of my mind.I'll try to flush it out, but with 125,000 on the lowwer end a tear down seems a little fruitless. Since I allready have alot of new parts including regulator and injection unit a Jasper short block may be in order. I really take care of the truck, not a mark on. Probabaly one of the best I've seen. Owned it since it was new. Thanks again, I'll let you know how I make out.I'm glad I found your sight!
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Tuesday, January 26th, 2010 AT 8:53 AM
Tiny
PEAR69
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It's not a lower end tear down -- it's just the intake. If you have already replaced the injector unit then it should be pretty easy. Leave the upper intake manifold (the plastic cover over the injector unit) bolted onto the lower intake -- just remove the lower intake bolts - 4 on each side - to remove the lower "intake". Your intake system has an upper and a lower. The upper part can remain on when the lower is removed. Just don't over torque the lower bolts when you put it back on.
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Tuesday, January 26th, 2010 AT 2:24 PM
Tiny
CRAZNDN
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I'm going to try the method you have suggested.I just meant the eventuality of the problem if I am unsuccessful with the flushing. Thanks again.
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Tuesday, January 26th, 2010 AT 6:50 PM
Tiny
CRAZNDN
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I was waiting for the weather to break to start my flushing project since my garage is not heated, and a new symptom has arose. I am now having coolant and oil leaking from both front corners of the lower manifold gasket. Which means to me manifold vaccum leak, in turn retarded timing in a harder pull, hence rise in temp. Under acceleration. Correct?
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Thursday, February 18th, 2010 AT 8:10 PM
Tiny
PEAR69
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Your engine is showing all the signs of (what I call) GM Dexcool destruction. The temp. Rise, plugged radiator, and now failing lower intake gasket are all of the typical signs. There is no doubt about it now - you must replace the lower intake gasket ASAP. The coolant will eventually leak into the oil and before you know it, your engine will have non-repairable damage. I am sure you know oil and engine coolant DO NOT mix.I do suggest the following (only because it is only a little more work and you will have the intake removed) remove the heads and replace the head gaskets and valve seals. It is only a little more work and it is relatively easy to do. You can get a total kit which includes lower intake gaskets, head gaskets, head bolts, valve seals, and everything to complete the job. Fel-pro makes the kit.
Some tips are: always clean the head bolt threads (in the block) with a tap, get some copper seal spray from permatex and spray it on both sides of the head gaskets (let it dry before installing), DO NOT over tighten the lower intake bolts (spec is 88 INCH pounds which is like 7 foot pounds), use gray silicone for the front and rear sealing of the lower intake -- and allow at least 24 hours for the silicone to dry.
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Thursday, February 18th, 2010 AT 11:34 PM
Tiny
PEAR69
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One more thing -- use prestone dexcool coolant in the engine. It is not the GM version and works much better than GMs' version.
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Thursday, February 18th, 2010 AT 11:36 PM

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