98 Forrester with Overheating Cooling System

[mattfrombedford]

98 Forrester with 149K miles.

 

After sifting through the posts on overheating engines, I have a pretty good idea that my head gaskets may be the problem but there are some confusing symtoms of my problem that perhaps maybe someone out there can shed light on for me.

 

First noticed the problem after a two hour highway drive. Temperature sensor was spiked and coolant spraying out of the engine from unknown source. There were no broken hoses so it was either coming out of the coolant reservoir or the radiator cap. The radiator cap was COLD. The outlet hose was HOT and there was no heat coming out of the car heating system. This sort of indicates no flow right?

 

OK so I took it to the shop(mom & pop place, not a Subaru Dealer), they replaced the thermostat first - still overheating- and then replaced the radiator assuming it was blocked. Mechanic drove it around town for some time no overheating. I got ready to drive it home and five minutes on the expressway, the temperature gage spikes again. This time I am getting heat from the car heater and if fact run it to try to get the heat off the engine as I limp home. Same thing however. Coolant blown inside the engine, COLD radiator cap and Hot exit hose. Belts around the water pump appear to be fine so at first glance, that is not siezed but is it possible that the impeller is somehow busted and the pump still turning freely? Head gasket would not totally restrict the flow would it? I would think that the Cap on the radiator would at least be warm? Also, if the lower intake hose was collapsing, the radiator would have been a little warm as well. I haven't checked the oil or coolant for contamination and will do so shortly so that will help in diagnosis.

 

Anyway, it is back at the shop and I am a little nervous that my mechanic may be a bit out of his element as he has never worked on this type of car. If it does turn out to be head gaskets, is this a job he could handle? He is a good mechanic but not versed in the Subaru engine. I don't know my way around the modern car engines either so I am in an uncomfortable position at this point.

 

Thank you to anyone who takes time to respond to this. I really appreciate your time

[The Dude]

If the replacement radiator cap was genuine Subaru, it sure sounds like a classic blown head gasket to me. You could have the coolant "sniffed" for combustion gases if you wish to confirm the diagnosis.

Phase I head gasket replacement has been successfully done by a number of owners on this board. Most of the owners were "shade tree" amateur mechanics. Therefore, a compentent and experienced professional mechanic SHOULD be able to handle the job. But you know your mechanic personally. Will he stand tall if something goes wrong with the head gasket repair?

[OB99W]

Unfortunately, it's likely that HGs are the problem. That doesn't mean a defective radiator cap, thermostat, or water pump couldn't cause such symptoms, but it's less likely. By the way, anyone replacing those parts would do well to use OEM ones.

 

As to the lack of heat from the heater - "no flow" can either mean a blockage or that there isn't much to flow; the latter is more likely. When it comes to blown HGs, it's more an issue of what they don't block than what they do.

 

Looking at the accessory drive belts won't tell you if the water pump is being properly driven, because they don't drive it. However, since the engine seems to run okay outside of the coolant spewing, it's likely that the timing belt, which does drive the pump, is not the cause of this problem.

 

If the coolant reservoir becomes full (the level normally falls within a specified range) when the problem occurs, and especially if much of it isn't pulled back into the cooling system as things cool down, that's typically an indication of leaking HGs.

 

Subaru engines are a bit "different". While any "good" mechanic could probably do the HG work, one experienced on Subaru engines would likely be able to complete the job faster and with less grief. Just knowing how to purge the cooling system of air after doing all the work can mean the difference between success and rework/failure. If your current mechanic replaced the radiator "assuming it was blocked", rather than doing a flow test, I'd be a bit leery of going back there for major work.

 

Best of luck.

[mattfrombedford]

Thanks Dude, I'll talk to the Mechanic about sniffing the coolant. Not understaning the mechanics of the motor itself, why would the flow be restricted in the overall system as a result as a result of the gasket being comprimised?

If it is an ignorant question, excuse it in advance :-\

 

Thanks man

[mattfrombedford]

I forgot to mention in the first post that I only seemed to loose a little bit of coolant. maybe less than half a gallon. The overheating was due to no flow as oppose to no coolant.

 

I'll post the final solution so folks can see the complete story.

 

thanks much guys.

 

m

[cookie]

the coolant sniffer does not always work on these cars. Probably because they vent the gas and seal back up while cold. On the other hand I am told they don't give false positives.

Your coolant will not circulate becuse the coolant at the top is replaced by combustion gas.

You have to remove the timing belt to replace the head gaskets. The only other likely culprit is the water pump. Inspect it while you have the belt off and if the impeller was not turning try a new pump before doing the head gaskets.