: 97 overheating update/helms/questions

06-01-04, 05:43 PM
Thought I'd post and update and let you guys know what the dealer found. Had it back to dealer last Friday, and they agreed to pay for diagnostics since I only put 3300 miles on the 97 ETC since last October. Anyhow, it took three hours!!!

Just a quick rundown: the car only overheated after some hard running uphill, or some long running up a slight grade. The mechanic did the pressure test as everyone recommended, with everything checking out OK. He also looked for exhaust gases in the coolant, everything OK there. At that point, the service manager got me involved directly with the mechanic, and I explained the symptoms and exactly when they occurred. He ran the test a third time (!), only he let the car get good and hot sitting there, and I believe he blocked off the radiator too. Anyhow, he finally got some exhaust gases in the coolant after the engine got real warm. His diagnosis: the head gaskets are going, but not shot yet.

The cost of repair: $2800 if they do it (and they'll pay the first $1000), or they'll give me all the parts, and loan me the timesert tools, if I do it myself. Since I feel mechanically inclined (and I sure as hell don't have $1800), I'm going to tackle this myself. Which brings me to these questions:
1) Would addition of Bars Leak powder work, or just delay the inevitable until I'm on a long trip and in the middle of nowhere.
2) Everyone recommends "Helms" manuals: which ones??? They list about a dozen on their web site, and I only want to get the ones I need.
3) I also have a oil leak at the lower pan gasket: should I do just this one, or replace all of them while I have the thing out.
4) Any other tips or tricks of the trade?? Anything else I should replace?? The dealer recommended a flush after the works done, something about getting coolant in the oil. Anyone else had a problem, or is just being extra careful going to work??

Lastly, I want to thank everyone for helping. God, I love this car and want to keep it a long time, and since it's only got 79K miles on it, I figure it's money well spent. Look forward to hearing from everyone, and thanks again.

06-01-04, 09:24 PM
The manuals are the factory service manuals. Helms is the distributor. You should check Ebay before you order them from Helms as you'll probably save some money at ebay. There are 3 manuals in the set. Get all 3...the price should be for all 3.

I've done 2 by dropping the cradle out the bottom and I wouldn't consider pulling it out the top. Once the cradle is out you have a lot of room and everything is easy to work on. Some guys pull just the engine but on this model I think that is the hard way of doing it! You decide which way you are comfortable.

You don't have to open the brake lines but you will have to open the AC lines. You have r134 so it should be easy to get it recharged. If you drop the cradle you don't have to pull the hood off.

You will be replacing the oil and water so I don't think an additional flush is needed.

Here's the info I put up. It has all the info on tools etc.


06-05-04, 05:56 PM

Thanks for the help, and I'll admit this is going to be interesting. Hope to start over the Father's day weekend, no real hurry since my beater gets me around. Have another question: I checked helms, they want $120 for the set (YOWZA!!). Haven't found a set on ebay, but I HAVE found a two book set of factory service manuals - will these work? Actually, I've found two sets, been outbid on one. You get a chance, let me know, and thanks again.

06-05-04, 10:07 PM
Checking the coolant for "exhaust gases" is notoriously inaccurate....especially with DexCool. Do not rely on this to start ripping the engine apart to do the head gaskets.

A pressure test of the combustion chambers is the ONLY sure way to identify a head gasket problem. Make an adapter out of an old spark plug shell or use the adapter from a compression gauge. Apply 120 PSI to the combustion chamber thru the spark plug port and watch the cooling system for bubbling. If the cylinders hold pressure without leaking into the cooling system (as evidenced by bubbling coolant) then the head gaskets are fine.

Head gaskets rarely if ever fail suddenly or catostrophically. I know of at least one Northstar that had the symptoms that you describe that checked positively for the head gasket leaking and then ran for about 80K further using the BarsLeaks (to excess at times....LOL) Put at least six of the GM coolant supplement pellets into the radiator hose (NOT the surge tank) or use two tubes of the BarsLeaks "golden seal" powder. NO substitutes. Use more if required. If it is a head gasket it will have to come apart at some time so it would be hard to put too much of the sealer into the system as it can't really hurt anything.....

I assume you have checked the obvious like the water pump drive belt, the water pump drive belt tensioner, the vapor vent line for positive flow and venting and the coolant concentration for a 50/50 mix. Any of these could cause the same symptoms you describe and have been described in detail in previous posts.

06-06-04, 09:41 AM

As you read, the mechanic said he did the pressure test - how much pressure I didn't ask, and it took him three tries to get the "exhaust gas in the coolant" result. I'll get my hands on an old plug, and make an adapter - would you recommend the test hot or cold?? Water pump belt is good, tensioner is good, that hose that runs from ? to the surge tank (3/8" hose) pumps coolant when started, thermostat was new in fall (and car sat most of winter). As far as 50/50, I can't get my hands on a refractometer of that scale, but I'm assuming (and we know what happens when we do that!!) that the mechanic checked it. Like I said, it only happens under a load: as when running for a while, hit a steep hill or really long grade at a decent speed. I was thinking about putting two tubes of the Bars Leak in, just to see if it would help. But I do get the sweet smelling exhaust if it runs setting in the driveway, so I don't know. If I didn't like this car so damn much, I'd trade it in a heartbeat since I want a dependable ride when I go to car shows and such (and the ladies think it's hot too - too bad the driver ain't). Anyhow, any more opinions are appreciated, and thanks for everyones help.

06-06-04, 01:15 PM
I find it rare for a mechanic to do the pressure test of the cylinders as I describe it. Usually they will do a compression test...which is pretty useless looking for a head gasket...or the "pressure test" they describe is a pressure test of the cooling system...not of the combustion chambers as I described. You have to find out what they did.....

Another quick check that you can do yourself is to get a cooling system pressure checker and pump the cooling system up to 15 PSI and let it sit. Do this with the cooling system full and the engine cold. While it is sitting...I am assuming there are no external leaks at this point....pull the spark plugs. Let the engine sit for 2-3 hours with pressure at 15PSI in the cooling system. Then spin the engine over with the plugs out with the starter. Watch the spark plug ports for coolant. If a head gasket is leaking it is likely that coolant will find it's way into the chambers as the engine sits with pressure on the cooling system and the engine off. I still like the pressure test of the combustion chambers with shop air better but this test is good too.

Definitely try the sealer in the system. It cannot hurt anything and it may stem the seepage (if there is some) until you can better orchestrate the head gasket job if needed.

Do NOT assume that the coolant is 50/50. Check it with a refractometer. Most any good shop has a refractometer for checking coolant concentration..... Or...drain the coolant and refill with a known premix of 50/50. Only way to be sure.

One other poster several months ago had boiling and overheating problems and found that the coolant was only about 20% instead of 50%. Putting 50/50 into the system cured the problem immediately...and the system had just been drained and "flushed" by a garage before he bought the car....duh..... I have seen this several times before so do not assume that someone got the coolant mix correct.

06-06-04, 09:27 PM
OK Bbob, thanks for the info. In the event I can't get my grubby paws on a refractometer, I'll drain the system and fill with 50/50 Dexcool and distilled water. One question: what's the best way to drain?? Lower radiator hose?? If I only take the hose off, I'll miss the coolant in the engine (or at least above the thermostat). If I refill, I'm in the same boat I'm in now. Obviously, I need to get the maximum amount of existing coolant out, so what's best.

I'm still going to work on the pressure test if I can lay my hands on an old plug, or get the compression tester fitting. 120# of air is no problem, but hot or cold engine?? If the mechanic is right in that it has to be really warm, should I do the pressure test under the same conditions, or if the gasket is going bad it wouldn't matter.

Due to your wisdom, I'm beginning to feel a little better about this whole thing, and maybe it isn't as bad as it seems. I'm keeping my fingers crossed, and thanks.

06-06-04, 09:33 PM
bobinski is the best and he knows his stuff

06-06-04, 10:29 PM
Pressure test the combustion chambers cold or hot...it really doesn't matter. If the head gasket is starting to go the 120 PSI constant pressure will find the leak and it will show up in the coolant as bubbling.

Just take the bottom hose off and use shop air to blow thru the hose to purge as much coolant from the system as possible.

06-09-04, 11:03 PM
KD makes a tool called an air hold if I remember correctly and it was primarily designed to put shop air in a cylinder to keep the valves closed for changing valve seals with out pulling the heads. They are about $5 each or a set of two. As for breaking up an old plug ... I was never successful doing that when I tried. That ceramic is very hard and cracks easily but doesn't come out easily for me. Another posibility is that I have seen compression gauges that the gauge snaped off with a quick disconnect like an air hose. IF you are so luck to have a matching air hose you are all done. I think the harbor freight $15 compression guage does that.

Now I have a tough question ... What is the easiest way to do a compression test on a 4.9L or to change the plugs? I still have not mastered or seen an easy way to do this. Last time I droped the rear of the engine cradle and that gave me enough room to do it from underneath as I lay in the street in front of my house ... Actually last time I had the heads off changing the head gaskets and on reassembly with the rocker arm support bar off access was easy. But it took me many hours to figure out how to reassemble that 3d puzzle as I hooked up the fuel rails first instead of last. My Dad's 98 Deville Northstar looks easy in comparison. It looks like just remove the coil pack and go to pulling plug wires.