Cools at high RPMs only, I don't get it!-95 Achieva

[Quad4]

I have a 95 Achieva, with the supposedly more reliable transition 2.3 Quad4. When it idles or runs under 3000 RPM, the engine tends to overheat, when you drive it like you stole it, it's ok. Some have suggested that my head gasket is about to blow out on me but the guy I bought it from says it's been that way for months. I've also been told that if you don't bleed the cooling system on certain cars, you can end up with an air bubble in the water pump and that can cause a pressure loss at low RPM. It doesn't loose coolant, it doesn't smoke and the oil and coolant are normal in color, smell and texture + compression is good on all 4 cylinders. Also, the check engine lamp sometimes lights up and the heater seems to be cooler when the engine gets too hot. I suspect a clog in the cooling system due to the fact that theres green prestone in there and not dex-cool. I really want to keep the car, I got it really cheap and besides that problem, it's like new. Any help will be greatly appreciated! Also, a head gasket job can take up to ten hours on this model so if the gasket's blown, I'll be looking for a W41. If you know where I can find one, let me know!

[Blaze_316_316]

Let me say this first you will never in your life find another W41. periode , I been searching canada for 1 for last 4 yrs no luck what so ever, you truely have the fastest stock Quad 4 H.O., 190 hp. your Quad 4 has a better computer and cams, then any basic Quad 4 HO, specs aside, she over heats at low rpm? well first things first are your fans kicking in @ all? seems to me the higher you rev it the harder your water pump is working(timing chain driven), so it cools down by moving coolent quicker... determine if your fans are working properly if they are not, start at the fuse block, or check for a sticky relay? if fans kick in, when was last time you changed your thermostat? it maybe stuck half way open or closed! due to your no heat problem, i don't wanna say it but a plugged up Heater Core is a possibility(knock on wood)

[xeroinfinity]

Welcome to AF Quad4.

I would agree with Blaze, confirm the fans are running.
It should kick on at 106°C (223°F) low speed, high speed 110°C (230°F) or when the AC is on.

A good cooling system flush and a new thermostat might help too.

[Quad4]

The thermostat is new and the fan works properly, will check heater core...

[Blaze_316_316]

well i wouldn;t be checking your heater core unless you replace it at same time b/c it could be like a 5 hr job ripping your dash apart... and if u do this DISCONNECT your NEG (-) on battery, Air bags could take your life... Try a Coolent Pressure test see if it hold pressure if doesn't very well be a head gasket you say your not burning coolent right? another suggestion is pull the cover and plugs out and turn it over it will shoot anti-freeze out the plug holes if infact you have no anti-freeze in your oil, if these simple little checks pass then i would give it a nice flush, you may have a somthing pluged like you say... let me kno

[Quad4]

Changed fluid and thermostat as directed by GM. Bubbles in the coolant when she runs. Also found some reddish deposits in the coolant reserve tank. Head gasket is definately to blame. Stopped using the car to prevent damage to head and cooling system. Is choosing Felpro over stock GM gaskets really worthwhile? Also, since the engine is being pulled out of the car, should I change any other parts, regardless of condition as to prevent future troubles? I'm not really familiar with these engines, I've had more V6s than fours and this will be the first time I'll be taking an engine apart, usually it gets replaced, but this one still runs real good. I've got a Haynes manual and some help from someone with more knowledge and experience than me so it should be OK.

[Blaze_316_316]

Quick Question why would you pull the motor? did u bend valves or fry rings?

[xeroinfinity]

Fel pro gaskets are great IMO.
I rarely use any factory gaskets as they are expesive and usually suck!

You dont need to pull the motor to do this job, but I would look at the water pump as I'm pretty sure its inside the front cover.

I'd inspect the timing chain and tensioners for wear and if they are stretch, I'd replace them too.

[Blaze_316_316]

i would change the water pump but its not inside the timing cover its just a gear inside the timing cover, that has splines on back side, running the pump,the water pump is on the firwall side under the exhaust... **NOT DO NOT PRY ON THE TIMING COVER!** Remeber there is 3 studs on the back side on timing cover, connecting the water pump to the gear. 2/3 down the back side on the timing cover.. I heard too many stories of these weak covers breaking due to prying. also remeber 4 bolts on bottom of oil pan, connecting timing cover. Like xeroinfinity says check the timing chain if shes over 200,000 km it could use a new tensior and chain/Guides x3 (do not use silicone when installing your timing cover** you may block important oil ports running your tensior**)

ps: You don;t have to pull the motor

[Quad4]

I thought you had to take it out to take it apart. Like I said before, all the engine needs is a head gasket to run like new, but changing the water pump and the timing chain and tensioner won't hurt either, she's got 188,000kms. I'd like to thank you all for your help and suggestions. I've changed fuel tanks, steering pumps, brakes, wheel bearings, shocks and a whole lotta crap on old cars but I never changed anything this serious. It'll be like a challenge and a learning experience for me. I'll be letting you know when I'm done. Once again, thanks alot, you've been really helpful.

Good driving!

[Blaze_316_316]

If you run into any problems at all give me a email blaze_316_316@hotmail.com most ppl run into timing chain instalation problems and get really frustrated, i can help. hope to hear from ya again on forums