Head gasket replacement - Take 2 (damn!) [Archive] - SaabCentral Forums

: Head gasket replacement - Take 2 (damn!)

2nd October 2006, 12:55 PM
Hello all...I need some help!

I spent the last year doing an engine rebuild in my 87 SPG on weekends/evenings :cheesy:. Sven had 400,00km (250,000mi) on him and the engine/tranny gasket blew as did the lower rad hose at the water pump under the intake manifold, otherwise he was awesome with no smoking or oil consumption. I love to tinker and despite being a girl who had never done an engine rebuild (or even seen one!), I got er done...I thought!

The head was sent to a machine shop and done professionally and I suspect they resurfaced it. So much time has passed they can't say for 100% sure, but think they did as it is pretty standard. I did not send the short block in for machining, just did the pistons, bearings, etc in my garage. SO... I put it all together a couple of months ago and have had several problems including...

Vacuum readings of about 5 (normal should be 13 to 20 I think) with a hunting, choppy idle. He often stalls when you give him gas and the idle drops down. He has no power to the point of not being drivable.:cry: In addition a coolant leak at the head gasket. :evil:

So I opened up the valve cover and retorqued the head bolts (twice) with the 2nd run being somewhat beyond the proper level which reduced but did not stop the coolant leaks. Am I correct in suspecting the vacuum leak I have been chasing for the last couple of months might be at the head gasket? Would this be enough to produce the choppy, hunting idle and complete lack of power and stalling? Sven does start up easily and can hold the idle so not all is lost I hope! In fact he seems to be better (but not good) for the first minute (ie. he's cold) and then deteriorates.

So now I ask for advice. Could there be a sufficient mismatch of the head gasket surfaces with the head side being machined and the other side not being done to cause me this grief? I am not prepared to pull the engine again at this time...although I tend to get mad at him like this and put him away for a couple of months only to grudgingly return and have a go at him anyway:lol: . Currently, I have the head almost back off again but wondering where I will go. Can one use a gasket sealer carefully at the head gasket other than the on two ends as Bentley tells me to do - my leaks seemed to be on the exhaust side around cylinder 2 and 3, thus hoping the sealant will help fill any deviations caused by the surfacing? If some of the gasket sealer got into the cylinders I imagine that would be a big problem. I am going to use all new gaskets again and yet another set of head bolts just to be safe. Any advice on the use of sealant type and strategies?

Any other ideas on the suspected vaccum leak would be helpful if the head gasket is not the potential cause. I covered several things already like checking all the hoses - all vaccum hoses were replaced and intake manifold bushings etc replaced. I also retorqued intake manifold and other bolts, tested the AIC, AMM, O2/lambda sensor, blue top coolant sensor, etc. The head gasket might be all I have left as a cause. I didn't do a smoke or propane test, but since I knew I needed to redo the head gasket, I figured I would have to recheck everything at the end again anyway if it is still a problem.


2nd October 2006, 01:56 PM
Karen -

there are a couple possibilities - sorry to say they're not attractive -

1) the head was stored incorrectly (laying across a couple 2*4's, for example) and gravity did its thing (gave it a slight bow)
2) the head was incorrectly resurfaced - if they didn't blanchard grind it "true flat" they could have introduced a problem.

On the less serious side there's ....

1) you didn't clean all the old gasket material off of the block
2) you didn't follow the correct torque sequence when you re-installed the head
3) you didn't torque the head correctly - compromised the head gasket - then re-torqued (but as the gasket was irregular it didn't help).
4) they did cut the head - and your head bolts are bottoming out in the block before you REALLY get the required clamping force - if you re-used the old head bolts this is a possibility - bolts stretch a bit when they're torqued - they stretch a bit every time they're re-torqued - on most engines it doesn't take much stretch to use up the depth of the holes -

If you're leaking coolant and getting low vacuum readings I think you'll need to re-pull the head - if you do - check for fresh machining marks (you should be able to see where it's been cut - the metal will look really "new") -

use a caliper to measure the thickness of the head, check the depth of the head bolt holes, measure the compressed thickness of the head gasket (there should be a spec somewhere for this) - then measure the head bolts - personally I'd use fresh head bolts .... oh - chase the threads in the block wiht a tap first also - so you don't get false torque readings from the bolt hitting a burr -

Sorry there's no quick fix - but - seeing as you've rebuilt the whole engine on your own anyhow - having the head off one more time should be a breeze!


PS - re-read your post - don't use gasket goop to try and seal a head gasket - it should seal through the pressure between the head and block - the goop will never withstand combustion pressure -

It is possible that you got a defective head gasket - by the way - when you pull the head it'll be obvious where the leak(s) were ...

2nd October 2006, 02:54 PM
Thanks Steve for the reply,

Yes I did store it on 2x4's for a couple of months, but the 2x4's were run along the length of the head vs. just on the ends, so less likely but possible. It was machined and put on the block within a couple of days of machining.
As for torquing, I used the correct sequence and directions from Elring, used new bolts, new gaskets everywhere. Surfaces were cleaned well, head done by the machine shop and the block by me with razor blade, gasket cleaner, carb cleaner and then 600grit sandpaper (the blue stuff that I use for final preps on my feeble attempts at autobody repairs:cheesy: ) to get the last residue off, followed by carb cleaner again. Not too likely any left as it was shiny clean all round. Didn't notice any marks,pits or gouges but I'll check again once it's off.

Really worried about a warp and will have to run a straight edge over it and check the depth with my caliper. Thanks for the tip on the head bolts bottoming, I kinda had a feel that one bolt at that location might not be wanting to torque more and was on the verge of stripping the threads if I tried (or heaven forbid has stripped a bit already!:o )- which might fit with bottoming out. If it is bottoming, I guess I could grind down the end of the head bolt to give me some more room.

Damn, Damn, Damn.:cry: PLease let it be a defective gasket... Homage will be paid the the Saab Gods if it is...I'll be so happy that I might not even get mad at Elring for making a crappy gasket. I sure don't want to buy a new head or have to fix the threads on the block - any tips there if one of the threads is stripped that might not result in the engine needing to be pulled? If Sven keeps this up, he is going to be a parts car for my '94 vert (Sonja).


2nd October 2006, 03:20 PM
Karen -

No problem - hey - girls who rebuild their own cars are cool - my first girlfriend rebuilt the motor in her 1948 Jeep ... something special about a gal with grease under her fingernails!

A lot of times when you clean stuff up on the mating surfaces - some of it'll go down the head bolt holes - you can depth-check them with a wooden dowel (or pencil) to make sure there's nothing down in there.

For length you can either grind the bolts (being careful to chase the threads when you're done so they'll start in well) or (sometimes) use washers under the headbolts to take up some length.

When you remove the bolts examine the threads - if anything stripped or started to strip it should be pretty obvious - so long as the bolt didn't go "tight - tighter - loose" you should be fine.

Also remember that torque specs differ between lubricated torque and dry torque - not sure what Saab specifies - but it does matter when you're cranking the bolts.

If there's a machine shop near where you live you can always take the head over and ask to use their flat table - they should have a very stable ultra flat heavy steel surface - failing that a thick plate of glass can be used to check for a flat surface. I always stored heads sitting on the end - but lengthwise on 2*4's should have been fine as well - and a couple days shouldn't have been enough time for gravity to do its thing - typically bad things happen if you store heads the wrong way for a protracted period of time.

Kinda sounds like the head gasket just didn't seal correctly - hopefully it's a defective gasket -

It'd be a shame for him to become a parts car - interesting how the gender assignment of vehicle names changes with the gender of the owner - I constantly refer to cars as "her" or "she" .....:roll:

best of luck


2nd October 2006, 06:10 PM
One day I hope to find a girl who can do head gasket changes for me! :lol:

I've got a couple of thoughts (speaking as someone who did a head gasket change without having the head checked and then had to do it again! :roll: )

Did you hold one of the new bolts up against the old ones? I replaced my head bolts and the new ones were longer than the old ones! I had to use washers under the heads or they bottomed out just as they started to tighten (it was really close.. I stripped 2 engines for parts and one had washers and one didnt!)

Secondly - before you strip it down again do a compression test. It is really easy and should tell you quite a bit! Even if you take it apart again it will help you know where to look.

I dont know a lot about these newfangled 16v engines but could your dodgy idle be caused by something other than the headwork. Dont you have AMM's and o2 sensors and possible vacuum leaks?

2nd October 2006, 08:37 PM

Well, on the plus side, the head bolts all look really good. The threads are all beautiful with no marks. Taking your comments to heart, I'm leaving the head on where it won't warp while I await the replacement gaskets/bolts and other sundries to arrive from eEuroparts - takes about 10 days to get here what with clearing customs and being on the opposite coast.

On your comment about the gender of cars, my '94 vert is a girl (Sonja) - partly 'cause she likes to drive around topless:cheesy:, mostly because a friend of mine dubbed her that after a very cheesy Arnold Schwarzenegger movie called Red Sonja from the 80's (Conan the Barbarian type movie). I was looking for a good Swedish name and was thinking along the lines of a female name, and that clinched it (let's face it Olga or Helga wasn't in the running for something as pretty as a red Saab convertible!). I was hoping to mate them and get free parts, but that hasn't worked yet;) . If it finally does happen, I imagine my husband will expect to get a 2nd Dodge Ram pickup in hot pink to match the patriot blue one. NOT!:roll:

Thanks again for your help and I'll post in a couple of weeks with how the saga turns out.