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Head gasket??

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bigjones

bigjones

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Hi folks,

Short story: A friend of a friend has come down to visit. The car (1500 Midget) overheated on the freeway last night.
This morning we went to take a look - car would not start and there was dirty oil in the coolant overflow bottle.

Had it towed back to my place where I've just done some compression tests (psi) - cold engine - (has a Weber carb so didn't know how to open the throttle):

#1: 142
#2: 100
#3: 79
#4: 112

and #1 again: 136

(all plugs removed)

I've a home-made leak-down tester someplace that I can use to analyze some more but what do you think so far?

Ideas, suggestions, most welcome as always.

Cheers!
 
Update:

Added a teaspoon of Castrol 20-50W to each cylinder:

Compression readings (psi):

#1: 150
#2: 110
#3: 87
#4: 124
 
Head needs to come off. Then send it to a machine shop for leak test and surfacing if needed and any valve work that is due.

recommend you find a local shop that deals with independent repair shops. They are more inclined to tell you what is needed and then what they recommend, rather than PRODUCTIOn shops that will tell you that it needs surfacing, new guides, new springs, new valves, etc...
 
Before you pull the head, hook up that leakdown tester. Best to have the full story.

If you find that you are leaking through an exhaust valve, you can tap on the valve rocker with a small hammer while blowing air into the cylinder. Sometimes this will blow out the carbon and give you good seal again.
 
BillM, Ron, Morris.

Many thanks for the replies.

I'll do the leak-down test and report back. Should be interesting!

That would be nice if I could fix the problem with a hammer!!!

As far as head gaskets go, am I right in the following concepts?

1. A head gasket can fail on its own accord. This would lead to over-heating.
2. Over-heating can lead to the head gasket failing.

Just trying to think ahead.

Cheers!
 
After the head is removed, I'd straight edge check both the block and head decks , anything .002" and under a gasket will take care of, anything more resurfacing needs to be done. The design of the 1500 head gasket was to better seal around the cylinders, but the ironic thing is the head gasket seem to be a weak point on the 1500s.
 
Thanks for the info, Hap. I'll certainly use a straight edge on the block and head to check for flatness.

Cheers!
 
Weber.jpg


Results of the leak-down test (stone cold engine):

#1 went from 80 psi to about 77 psi, the only air escaping was from the valve cover.

With #2,3,4, however, with the pistons maintained at TDC, there was serious bubbling out of the radiator overflow bottle (with psi dropping approx. 0, 15, 25, respectively)

Looks like the head is coming off, right?

OK, as you can see, it has a Weber. I'm more familar, by necessity :laugh: , with ZS and SU. When I pulled off the head on the ole TR3, I could leave the carbs and manifolds intact (unbolted from the head of course) just dangling in mid air. I'm thinking I can do the same here.

Any advice on the disassembly would be most appreciated here - this is not my car and I don't want to mess up.

Incidentally, I noticed that the valve clearances were very tight - would this have caused overheating which may have led to the gasket blowing or can a gasket just decide, on it's own, to loose interest?

Cheers!
PS. Just checked the thermostat. It's a 180F and it seems to be opening at about 183F, according to my barbeque thermometer. So we can rule that out. I'm thinking of putting in a 160F, seeing the car lives in Virginia and it is mighty hot here in NC, which, of course, is next door.
 
Yep, right, head is comming off for a new gasket and, and check the deck and the head for straightness with a steel straight edge. Also check valves for burning etc while you are in there.

Yep tight valves could cause overheating depending how tight of course. But yes.
 
Well, it was a bit of a pig but it is off. :thirsty:

I'm a bit disappointed that, to me, there is no obvious damage to the gasket. What is the opinion?
Top:
GasketTop.jpg

Bottom:
GasketBottom.jpg

Head.jpg

Block.jpg

I'll get the straight edge out after I get my breathe back :laugh:
 
I'll bet that when you pull out the valves (especially #1 valves) you will find crud, burning or a hole on the backside (probably the exhaust valve).
Bill
 
Adrian, I don't see anything obvious on the head gasket pictures but closer examination of the gasket may reveal some form of witness marks.

Contrary to the advice of others who suspect valve issues, I would focus on the flatness of the head and block since you observed oil in the coolant and your leak down test showed a path into the water jacket on cylinders 2 through 4.

That said, while you are looking at the head, I would certainly take the time to check the valves since the head is off the engine. An absolutely worst case scenario would be cracking in the head that has connected the combustion chambers to the water jacket and oil galleries.

I don't know any machine shops in Durham or Wake Forest. As late as 8 years ago I was still using Walker Automotive off of Six Forks Road in Raleigh for machine shop work.
 
All those places on the block and head where you do not have to scrape off remnants of head gasket... that's where it was leaking. :wink:
 
OK, thanks folks.

Still trying to clean the head up so I can lay a straight edge on it.

Doug - here is a shop I used about 10 years ago for the TR3 head. They had reasonable prices and the car is still running strong - the TR3 head was also a little tricky to work on as well (valve stem clearances) so they did well.

I'll give them a call tomorrow. The gal I'm doing this for isn't rolling in money but I'm thinking I should at least have it cleaned and checked for cracks, valves and flatness.

More at ten.

Cheers!
 
Now, clean things up, put a bit of oil on top of pistons and on top of block.

Turning attention to the head. I would have valves removed, guides removed, boiled, leveled, new guides, valves ground, paint it preaty and, and.

with a new gasket replace it if the top of the block checks flat as well.

I have to assume that when whoever does the head is finished they are going to be able to tell you what the prob is was. Suggest to them that it may be cracked, warped or a bad valve.

Agree with all above that it may just be a durn head gasket.

Last but not least let us know what someone found.
 
Jack,

Thanks for the encouragement.

OK, took a straight edge to the cleaned head and I could slide a 4 thou feeler gauge in there between 2 and 3 cylinders.

I'm off to the shop to get it skimmed and the valves checked.

Cheers!
 
Even after having my head and block skimmed, I still managed to blow a head gasket. The last time I put a head gasket on, I used Permatex spray on head gasket sealer and everything is holding strong. I highly recommend you do the same.
 
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